电气专业毕业设计外文翻译

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电气工程及其自动化专业毕业论文外文翻译

本科毕业设计(论文)中英文对照翻译院(系部）工程学院专业名称电气工程及其自动化年级班级 11级2班学生姓名蔡李良指导老师赵波Infrared Remote Control SystemAbstractRed outside data correspondence the technique be currently within the scope of world drive extensive usage of a kind of wireless conjunction technique, drive numerous hardware and software platform support。

Red outside the transceiver product have cost low，small scaled turn, the baud rate be quick，point to point SSL, be free from electromagnetism thousand Raos etc. characteristics，can realization information at dissimilarity of the product fast，convenience，safely exchange and transmission, at short distance wireless deliver aspect to own very obvious of advantage。

Along with red outside the data deliver a technique more and more mature, the cost descend, red outside the transceiver necessarily will get at the short distance communication realm more extensive of application.The purpose that design this s ystem is transmit customer’s operation information with infrared rays for transmit media, then demodulate original signal with receive circuit。

电气毕业设计用外文翻译(中英文对照)

The Transformer on load ﹠Introduction to DC Machine sThe Transformer on loadIt has been shown that a primary input voltage 1V can be transformed to any desired open-circuit secondary voltage 2E by a suitable choice of turns ratio. 2E is available for circulating a load current impedance. For the moment, a lagging power factor will be considered. The secondary current and the resulting ampere-turns 22N I will change the flux, tending to demagnetize the core, reduce m Φ and with it 1E . Because the primary leakage impedance drop is so low, a small alteration to 1E will cause an appreciable increase of primary current from 0I to a new value of 1I equal to ()()i jX R E V ++111/. The extra primary current and ampere-turns nearly cancel the whole of the secondary ampere-turns. This being so , the mutual flux suffers only a slight modification and requires practically the same net ampere-turns 10N I as on no load. The total primary ampere-turns are increased by an amount 22N I necessary to neutralize the same amount of secondary ampere-turns. In the vector equation , 102211N I N I N I =+; alternatively, 221011N I N I N I -=. At full load, the current 0I is only about 5% of the full-load current and so 1I is nearly equal to 122/N N I . Because in mind that 2121/N N E E =, the input kV A which is approximately 11I E is also approximately equal to the output kV A, 22I E .The physical current has increased, and with in the primary leakage flux to which it is proportional. The total flux linking the primary ,111Φ=Φ+Φ=Φm p , is shown unchanged because the total back e.m.f.,（dt d N E /111Φ-）is still equal and opposite to 1V . However, there has been a redistribution of flux and the mutual component has fallen due to the increase of 1Φ with 1I . Although the change is small, the secondary demand could not be met without a mutual flux and e.m.f. alteration to permit primary current to change. The net flux s Φlinking the secondary winding has been further reduced by the establishment of secondary leakage flux due to 2I , and this opposes m Φ. Although m Φ and2Φ are indicated separately , they combine to one resultant in the core which will be downwards at the instant shown. Thus the secondary terminal voltage is reduced to dt d N V S /22Φ-= which can be considered in two components, i.e. dt d N dt d N V m //2222Φ-Φ-=or vectorially 2222I jX E V -=. As for the primary, 2Φ is responsible for a substantially constant secondaryleakage inductance 222222/Λ=ΦN i N . It will be noticed that the primary leakage flux is responsiblefor part of the change in the secondary terminal voltage due to its effects on the mutual flux. The two leakage fluxes are closely related; 2Φ, for example, by its demagnetizing action on m Φ has caused the changes on the primary side which led to the establishment of primary leakage flux.If a low enough leading power factor is considered, the total secondary flux and the mutual flux are increased causing the secondary terminal voltage to rise with load. p Φ is unchanged in magnitude from the no load condition since, neglecting resistance, it still has to provide a total back e.m.f. equal to 1V . It is virtually the same as 11Φ, though now produced by the combined effect of primary and secondary ampere-turns. The mutual flux must still change with load to give a change of 1E and permit more primary current to flow. 1E has increased this time but due to the vector combination with 1V there is still an increase of primary current.Two more points should be made about the figures. Firstly, a unity turns ratio has been assumed for convenience so that '21E E =. Secondly, the physical picture is drawn for a different instant of time from the vector diagrams which show 0=Φm , if the horizontal axis is taken as usual, to be the zero time reference. There are instants in the cycle when primary leakage flux is zero, when the secondary leakage flux is zero, and when primary and secondary leakage flux is zero, and when primary and secondary leakage fluxes are in the same sense.The equivalent circuit already derived for the transformer with the secondary terminals open, can easily be extended to cover the loaded secondary by the addition of the secondary resistance and leakage reactance.Practically all transformers have a turns ratio different from unity although such an arrangement issometimes employed for the purposes of electrically isolating one circuit from another operating at the same voltage. To explain the case where 21N N ≠ the reaction of the secondary will be viewed from the primary winding. The reaction is experienced only in terms of the magnetizing force due to the secondary ampere-turns. There is no way of detecting from the primary side whether 2I is large and 2N small or vice versa, it is the product of current and turns which causes the reaction. Consequently, a secondary winding can be replaced by any number of different equivalent windings and load circuits which will give rise to an identical reaction on the primary .It is clearly convenient to change the secondary winding to an equivalent winding having the same number of turns 1N as the primary.With 2N changes to 1N , since the e.m.f.s are proportional to turns, 2212)/('E N N E = which is the same as 1E .For current, since the reaction ampere turns must be unchanged 1222'''N I N I = must be equal to 22N I .i.e. 2122)/(I N N I =.For impedance , since any secondary voltage V becomes V N N )/(21, and secondary current I becomes I N N )/(12, then any secondary impedance, including load impedance, must become I V N N I V /)/('/'221=. Consequently, 22212)/('R N N R = and 22212)/('X N N X = .If the primary turns are taken as reference turns, the process is called referring to the primary side. There are a few checks which can be made to see if the procedure outlined is valid.For example, the copper loss in the referred secondary winding must be the same as in the original secondary otherwise the primary would have to supply a different loss power. ''222R I must be equal to 222R I . ）222122122/()/(N N R N N I ∙∙ does in fact reduce to 222R I .Similarly the stored magnetic energy in the leakage field )2/1(2LI which is proportional to 22'X I will be found to check as ''22X I . The referred secondary 2212221222)/()/(''I E N N I N N E I E kVA =∙==.The argument is sound, though at first it may have seemed suspect. In fact, if the actual secondarywinding was removed physically from the core and replaced by the equivalent winding and load circuit designed to give the parameters 1N ,'2R ,'2X and '2I , measurements from the primary terminals would be unable to detect any difference in secondary ampere-turns, kVA demand or copper loss, under normal power frequency operation.There is no point in choosing any basis other than equal turns on primary and referred secondary, but it is sometimes convenient to refer the primary to the secondary winding. In this case, if all the subscript 1’s are interchanged for the subscript 2’s, the necessary referring constants are easily found; e.g. 2'1R R ≈,21'X X ≈; similarly 1'2R R ≈ and 12'X X ≈.The equivalent circuit for the general case where 21N N ≠ except that m r has been added to allow for iron loss and an ideal lossless transformation has been included before the secondary terminals to return '2V to 2V .All calculations of internal voltage and power losses are made before this ideal transformation is applied. The behaviour of a transformer as detected at both sets of terminals is the same as the behaviour detected at the corresponding terminals of this circuit when the appropriate parameters are inserted. The slightly different representation showing the coils 1N and 2N side by side with a core in between is only used for convenience. On the transformer itself, the coils are , of course , wound round the same core.Very little error is introduced if the magnetising branch is transferred to the primary terminals, but a few anomalies will arise. For example ,the current shown flowing through the primary impedance is no longer the whole of the primary current. The error is quite small since 0I is usually such a small fraction of 1I . Slightly different answers may be obtained to a particular problem depending on whether or not allowance is made for this error. With this simplified circuit, the primary and referred secondary impedances can be added to give: 221211)/(Re N N R R += and 221211)/(N N X X Xe +=It should be pointed out that the equivalent circuit as derived here is only valid for normal operation at power frequencies; capacitance effects must be taken into account whenever the rate of change of voltage would give rise to appreciable capacitance currents, dt CdV I c /=. They are important at high voltages and at frequencies much beyond 100 cycles/sec. A further point is not theonly possible equivalent circuit even for power frequencies .An alternative , treating the transformer as a three-or four-terminal network, gives rise to a representation which is just as accurate and has some advantages for the circuit engineer who treats all devices as circuit elements with certain transfer properties. The circuit on this basis would have a turns ratio having a phase shift as well as a magnitude change, and the impedances would not be the same as those of the windings. The circuit would not explain the phenomena within the device like the effects of saturation, so for an understanding of internal behaviour .There are two ways of looking at the equivalent circuit:(a) viewed from the primary as a sink but the referred load impedance connected across '2V ,or (b) viewed from the secondary as a source of constant voltage 1V with internal drops due to 1Re and 1Xe . The magnetizing branch is sometimes omitted in this representation and so the circuit reduces to a generator producing a constant voltage 1E (actually equal to 1V ) and having an internal impedance jX R + (actually equal to 11Re jXe +).In either case, the parameters could be referred to the secondary winding and this may save calculation time .The resistances and reactances can be obtained from two simple light load tests.Introduction to DC MachinesDC machines are characterized by their versatility. By means of various combination of shunt, series, and separately excited field windings they can be designed to display a wide variety of volt-ampere or speed-torque characteristics for both dynamic and steadystate operation. Because of the ease with which they can be controlled , systems of DC machines are often used in applications requiring a wide range of motor speeds or precise control of motor output.The essential features of a DC machine are shown schematically. The stator has salient poles and is excited by one or more field coils. The air-gap flux distribution created by the field winding is symmetrical about the centerline of the field poles. This axis is called the field axis or direct axis.As we know , the AC voltage generated in each rotating armature coil is converted to DC in the external armature terminals by means of a rotating commutator and stationary brushes to which the armature leads are connected. The commutator-brush combination forms a mechanical rectifier,resulting in a DC armature voltage as well as an armature m.m.f. wave which is fixed in space. The brushes are located so that commutation occurs when the coil sides are in the neutral zone , midway between the field poles. The axis of the armature m.m.f. wave then in 90 electrical degrees from the axis of the field poles, i.e., in the quadrature axis. In the schematic representation the brushes are shown in quarature axis because this is the position of the coils to which they are connected. The armature m.m.f. wave then is along the brush axis as shown.. (The geometrical position of the brushes in an actual machine is approximately 90 electrical degrees from their position in the schematic diagram because of the shape of the end connections to the commutator.)The magnetic torque and the speed voltage appearing at the brushes are independent of the spatial waveform of the flux distribution; for convenience we shall continue to assume a sinusoidal flux-density wave in the air gap. The torque can then be found from the magnetic field viewpoint.The torque can be expressed in terms of the interaction of the direct-axis air-gap flux per pole d Φ and the space-fundamental component 1a F of the armature m.m.f. wave . With the brushes in the quadrature axis, the angle between these fields is 90 electrical degrees, and its sine equals unity. For a P pole machine 12)2(2a d F P T ϕπ= In which the minus sign has been dropped because the positive direction of the torque can be determined from physical reasoning. The space fundamental 1a F of the sawtooth armature m.m.f. wave is 8/2π times its peak. Substitution in above equation then gives a d a a d a i K i mPC T ϕϕπ==2 Where a i =current in external armature circuit;a C =total number of conductors in armature winding;m =number of parallel paths through winding;And mPC K a a π2=Is a constant fixed by the design of the winding.The rectified voltage generated in the armature has already been discussed before for an elementary single-coil armature. The effect of distributing the winding in several slots is shown in figure ,in which each of the rectified sine waves is the voltage generated in one of the coils, commutation taking place at the moment when the coil sides are in the neutral zone. The generated voltage as observed from the brushes is the sum of the rectified voltages of all the coils in series between brushes and is shown by the rippling line labeled a e in figure. With a dozen or so commutator segments per pole, the ripple becomes very small and the average generated voltage observed from the brushes equals the sum of the average values of the rectified coil voltages. The rectified voltage a e between brushes, known also as the speed voltage, is m d a m d a a W K W mPC e ϕϕπ==2 Where a K is the design constant. The rectified voltage of a distributed winding has the same average value as that of a concentrated coil. The difference is that the ripple is greatly reduced.From the above equations, with all variable expressed in SI units:m a a Tw i e =This equation simply says that the instantaneous electric power associated with the speed voltage equals the instantaneous mechanical power associated with the magnetic torque , the direction of power flow being determined by whether the machine is acting as a motor or generator.The direct-axis air-gap flux is produced by the combined m.m.f. f f i N ∑ of the field windings, the flux-m.m.f. characteristic being the magnetization curve for the particular iron geometry of the machine. In the magnetization curve, it is assumed that the armature m.m.f. wave is perpendicular to the field axis. It will be necessary to reexamine this assumption later in this chapter, where the effects of saturation are investigated more thoroughly. Because the armature e.m.f. is proportional to flux timesspeed, it is usually more convenient to express the magnetization curve in terms of the armature e.m.f. 0a e at a constant speed 0m w . The voltage a e for a given flux at any other speed m w is proportional to the speed,i.e. 00a m m a e w w e Figure shows the magnetization curve with only one field winding excited. This curve can easily be obtained by test methods, no knowledge of any design details being required.Over a fairly wide range of excitation the reluctance of the iron is negligible compared with that of the air gap. In this region the flux is linearly proportional to the total m.m.f. of the field windings, the constant of proportionality being the direct-axis air-gap permeance.The outstanding advantages of DC machines arise from the wide variety of operating characteristics which can be obtained by selection of the method of excitation of the field windings. The field windings may be separately excited from an external DC source, or they may be self-excited; i.e., the machine may supply its own excitation. The method of excitation profoundly influences not only the steady-state characteristics, but also the dynamic behavior of the machine in control systems.The connection diagram of a separately excited generator is given. The required field current is a very small fraction of the rated armature current. A small amount of power in the field circuit may control a relatively large amount of power in the armature circuit; i.e., the generator is a power amplifier. Separately excited generators are often used in feedback control systems when control of the armature voltage over a wide range is required. The field windings of self-excited generators may be supplied in three different ways. The field may be connected in series with the armature, resulting in a shunt generator, or the field may be in two sections, one of which is connected in series and the other in shunt with the armature, resulting in a compound generator. With self-excited generators residual magnetism must be present in the machine iron to get the self-excitation process started.In the typical steady-state volt-ampere characteristics, constant-speed primemovers being assumed. The relation between the steady-state generated e.m.f. a E and the terminal voltage t V isa a a t R I E V -=Where a I is the armature current output and a R is the armature circuit resistance. In a generator, a E is large than t V ; and the electromagnetic torque T is a countertorque opposing rotation.The terminal voltage of a separately excited generator decreases slightly with increase in the load current, principally because of the voltage drop in the armature resistance. The field current of a series generator is the same as the load current, so that the air-gap flux and hence the voltage vary widely with load. As a consequence, series generators are not often used. The voltage of shunt generators drops off somewhat with load. Compound generators are normally connected so that the m.m.f. of the series winding aids that of the shunt winding. The advantage is that through the action of the series winding the flux per pole can increase with load, resulting in a voltage output which is nearly constant. Usually, shunt winding contains many turns of comparatively heavy conductor because it must carry the full armature current of the machine. The voltage of both shunt and compound generators can be controlled over reasonable limits by means of rheostats in the shunt field. Any of the methods of excitation used for generators can also be used for motors. In the typical steady-state speed-torque characteristics, it is assumed that the motor terminals are supplied from a constant-voltage source. In a motor the relation between the e.m.f. a E generated in the armature and the terminal voltage t V isa a a t R I E V +=Where a I is now the armature current input. The generated e.m.f. a E is now smaller than the terminal voltage t V , the armature current is in the opposite direction to that in a motor, and the electromagnetic torque is in the direction to sustain rotation ofthe armature.In shunt and separately excited motors the field flux is nearly constant. Consequently, increased torque must be accompanied by a very nearly proportional increase in armature current and hence by a small decrease in counter e.m.f. to allow this increased current through the small armature resistance. Since counter e.m.f. is determined by flux and speed, the speed must drop slightly. Like the squirrel-cage induction motor ,the shunt motor is substantially a constant-speed motor having about 5 percent drop in speed from no load to full load. Starting torque and maximum torque are limited by the armature current that can be commutated successfully.An outstanding advantage of the shunt motor is ease of speed control. With a rheostat in the shunt-field circuit, the field current and flux per pole can be varied at will, and variation of flux causes the inverse variation of speed to maintain counter e.m.f. approximately equal to the impressed terminal voltage. A maximum speed range of about 4 or 5 to 1 can be obtained by this method, the limitation again being commutating conditions. By variation of the impressed armature voltage, very wide speed ranges can be obtained.In the series motor, increase in load is accompanied by increase in the armature current and m.m.f. and the stator field flux (provided the iron is not completely saturated). Because flux increases with load, speed must drop in order to maintain the balance between impressed voltage and counter e.m.f.; moreover, the increase in armature current caused by increased torque is smaller than in the shunt motor because of the increased flux. The series motor is therefore a varying-speed motor with a markedly drooping speed-load characteristic. For applications requiring heavy torque overloads, this characteristic is particularly advantageous because the corresponding power overloads are held to more reasonable values by the associated speed drops. Very favorable starting characteristics also result from the increase in flux with increased armature current.In the compound motor the series field may be connected either cumulatively, so that its.m.m.f.adds to that of the shunt field, or differentially, so that it opposes. The differential connection is very rarely used. A cumulatively compounded motor hasspeed-load characteristic intermediate between those of a shunt and a series motor, the drop of speed with load depending on the relative number of ampere-turns in the shunt and series fields. It does not have the disadvantage of very high light-load speed associated with a series motor, but it retains to a considerable degree the advantages of series excitation.The application advantages of DC machines lie in the variety of performance characteristics offered by the possibilities of shunt, series, and compound excitation. Some of these characteristics have been touched upon briefly in this article. Still greater possibilities exist if additional sets of brushes are added so that other voltages can be obtained from the commutator. Thus the versatility of DC machine systems and their adaptability to control, both manual and automatic, are their outstanding features.负载运行的变压器及直流电机导论负载运行的变压器通过选择合适的匝数比，一次侧输入电压1V 可任意转换成所希望的二次侧开路电压2E 。

电气专业毕业设计外文翻译---电力系统自动化

外文资料翻译Power System AutomationPower system integration is the act of communication data to, or among IED s in the I&C system and remote users. Substation integration refers to combining data from the IED′s local to a substation so that there is a single point of contact in the substation for all of the I&C data. Poletop devices often communicate to the substation via wireless or fiber connections. Remote and local substation and feeder control is passed through the substation controller acting as a single point of contact. Some systems bypass the substation controller by using direct connections to the poletop devices, such as RTU s, protective relays, and controllers.Power system automation is the act of automatically controlling the power system via I&C devices. Substation automation refers to using IED data, control and automation capabilities within the substation, and control commands from remote users to control power system devices. Since true substation automation relies on substation integration, the terms are often used interchangeably.Power system automation includes processes associated with generation and delivery of power. A subset of the process deal with delivery of power at transmission and distribution levels, which is power delivery automation. Together, monitoring and control of power delivery system in the substation and on the poletop reduce the occurrence of outages and shorten the duration of outages that do occur. The IED′s, communications protocols, and communications methods described in previous sections, work together as a system to perform power system automation.Though each utility is unique, most consider power delivery automation of transmission and distribution substation and feeders to include : Supervisory Control and Data Acquisition(SCADA)-operatorsupervision and control;Distribution Automation-fault location, auto-isolation, auto-sectionalizing, and auto-restoration;Substation Automation-breaker failure, reclosing, battery monitoring, dead substation transfer, and substation load transfer;Energy Management System (EMS)-load flow, VAR and voltage monitoring and control, generation control, transformer and feeder load balancing;Fault analysis and device maintenance.System without automated control still have the advantages of remote monitoring and operator control of power system devices, which includes: Remote monitoring and control of circuit breakers and automated switches;Remote monitoring of non-automated switches and fuses;Remote monitoring and control of capacitor banks;Remote monitoring and voltage control;Remote power quality monitoring and control.IED s described in the overview are used to perform power system integration and automation. Most designs require that the one IED act as the substation controller and perform data acquisition and control of the other IED s. The substation controllers is often called upon to support system automation tasks as well. The communications industry uses the term client/server for a device that acts as a master, or client, retrieving data from some devices and then acts as a slaver, a server, sending this data to other devices. The client/server collecting and concentrating dynamically. A data concentrator creates a substation databases by collecting and concentrating dynamic data from several devices. In this fashion, essential subsets of data from each IED are forwarded to a master through one data transfer. The concentrator databases is used to pass data between IED s that are not directly connected.A substation archive client/server collects and archives data from several devices. The archive data is retrieved when it is convenient for the userto do so.The age of the IED s now in substations varies widely. Many of these IED s are still useful but lack the most recent protocols. A communications processor that can communicate with each IED via a unique baud rate and protocol extends the time that each IED is useful. Using a communications processor for substation integration also easily accommodates future IED s. It is rare for all existing IED s to be discarded during a substation integration upgrade project.The benefits of monitoring, remote control, and automation of power delivery include improved employee and public safety, and deferment of the cost of purchasing new equipment. Also, reduced operation and maintenance costs are realized through improved use of existing facilities and optimized performance of the power system through reduced losses associated with outages and improved voltage profile. Collection of information can result in better planning and system design, and increased customer satisfaction will result from improved responsiveness, service reliability, and power quality.Power system automation includes a variety of equipment. The principal items are listed and briefly described below.Instrument transformers are used to sense power system current and voltage. They are physically connected to power system apparatus and convert the actual power system signals, which includes high voltage and current magnitudes, down to lower signal levels.Transducers convert the analog output of an instrument transformer from one magnitude to another or from one value type to another, such as from an ac current to dc voltage.As the name implies, a remote terminal device, RTU, is an IED that can be installed in a remote location, and acts as a termination point for filed contacts. A dedicated pair of copper conductors are used to sense every contract and transducer value. These conductors originated at the power system device, are installed in trenches or overhead cable trays, and are thenterminated on panels within the RTU. The RTU can transfer collected data to other devices and receive data and control commands from other device through a serial port. User programmable RTUs are referred to as “smart RTUs.”A communication switch is a device that switches between several serial ports when it is told to do so. The remote user initiates communications with the port switch via a connection to the substation , typically a leased line or dial-up telephone connection. Once connected, the user can route their communication through the port switch to one of the connected substation IEDs. The port switch merely “passes through” the IED communication.A meter is an IED that is used to create accurate measurement of power system current, voltage, and power values. Metering values such as demand and peak are saved within the meter to create historical information about the activity of the power system.A digital fault recorder ,is an IED that records information about power system disturbances. It is capable of storing data in digital format when triggered by conditions detected on the power system. Harmonics, frequency, and voltage are examples of data captured by DFRs.Load tap changer are devices used to change the tap position on transformers. These devices work automatically or can be controlled via another local IED or form a remote operator or process.Recloser controllers remotely control the operation of automated reclosers and switches. These devices monitor and store power system conditions and determine when to perform control actions. They also accept commands form a remote operator or process.电力系统自动化电力系统集成是在I&C系统中的IED和远程用户之间进行数据通信的操作。

(完整版)电气专业中英文对照翻译毕业设计论文

优秀论文审核通过未经允许切勿外传Chapter 3 Digital Electronics3.1 IntroductionA circuit that employs a numerical signal in its operation is classified as a digital circuitputers,pocket calculators, digital instruments, and numerical control (NC) equipment are common applications of digital circuits. Practically unlimited quantities of digital information can be processed in short periods of time electronically. With operational speed of prime importance in electronics today,digital circuits are used more frequently.In this chapter, digital circuit applications are discussed.There are many types of digital circuits that electronics, including logic circuits, flip-flop circuits, counting circuits, and many others. The first sections of this unit discuss the number systems that are basic to digital circuit understanding. The remainder of the chapter introduces some of the types of digital circuits and explains Boolean algebra as it is applied to logic circuits.3.2 Digital Number SystemsThe most common number system used today is the decimal system,in which 10 digits are used for counting. The number of digits in the systemis called its base (or radix).The decimal system，therefore，the counting process. The largest digit that can be used in a specific place or location is determined by the base of the system. In the decimal system the first position to the left of the decimal point is called the units place. Any digit from 0 to 9 can be used in this place.When number values greater than 9 are used,they must be expressed with two or more places.The next position to the left of the units place in a decimal system is the tens place.The number 99 is the largest digital value that can be expressed by two places in the decimal system.Each place added to the left extends the number system by a power of 10.Any number can be expressed as a sum of weighted place values.The decimal number 2583,for example, is expressed as (2×1000)+(5×100)+(8×10)+(3×1).The decimal number system is commonly used in our daily lives. Electronically, the binary system.Electronically,the value of 0 can be associated with a low-voltage value or no voltage. The number 1 can then be associated with a voltage value larger than 0. Binary systems that use these voltage values are said to , this chapter.The two operational states of a binary system,1 and 0,are natural circuit conditions. When a circuit is turned off or the off, or 0,state. An electrical circuit that the on，or 1,state. By using transistor or ICs，it is electronically possible to change states in less than a microsecond. Electronic devices make it possible to manipulate millions of 0s and is in a second and thus to process information quickly.The basic principles of numbering used in decimal numbers apply ingeneral to binary numbers.The base of the binary system is 2,meaning that only the digits 0 and 1 are used to express place value. The first place to the left of the binary point,or starting point，represents the units，or is,location. Places to the left of the binary point are the powers of 2.Some of the place values in base 2 are 2º=1,2¹=2,2²=4,2³=8,2⁴=16,25=32,and 26=64.When bases other than 10 are used,the numbers should example.The number 100₂(read“one,zero,zero, base 2”)is equivalent to 4 in base 10,or 410.Starting with the first digit to the left of the binary point,this number this method of conversion a binary number to an equivalent decimal number，write down the binary number first. Starting at the binary point，indicate the decimal equivalent for each binary place location where a 1 is indicated. For each 0 in the binary number leave a blank space or indicate a 0 ' Add the place values and then record the decimal equivalent.The conversion of a decimal number to a binary equivalent is achieved by repetitive steps of division by the number 2.When the quotient is even with no remainder,a 0 is recorded.When the quotient process continues until the quotient is 0.The binary equivalent consists of the remainder values in the order last to first.3.2.2 Binary-coded Decimal (BCD) Number SystemWhen large numbers are indicated by binary numbers，they are difficult to use. For this reason，the Binary-Coded Decimal(BCD) method of counting was devised. In this system four binary digits are used to represent each decimal digit.To illustrate this procedure，the number 105，is converted to a BCD number.In binary numbers，To apply the BCD conversion process，the base 10 number is first divided into digits according to place values.The number 10510 gives the digits 1-0-5.Converting each displayed by this process with only 12 binary numbers. The between each group of digits is important when displaying BCD numbers.The largest digit to be displayed by any group of BCD numbers is 9.Six digits of a number-coding group are not used at all in this system.Because of this, the octal (base 8) and the binary form but usually display them in BCD,octal,or a base 8 system is 7. The place values starting at the left of the octal point are the powers of eight: 80=1,81=8,82=64,83=512,84=4096,and so on.The process of converting an octal number to a decimal number is the same as that used in the binary-to-decimal conversion process. In this method, equivalent decimal is 25810.Converting an octal number to an equivalent binary number is similar to the BCD conversion process. The octal number is first divided into digits according to place value. Each octal digit is then converted into an equivalent binary number using only three digits.Converting a decimal number to an octal number is a process of repetitive division by the number 8.After the quotient determined，the remainder is brought down as the place value.When the quotient is even with no remainder，a 0 is transferred to the place position.The number for converting 409810 to base 8 is 100028.Converting a binary number to an octal number is an importantconversion process of digital circuits. Binary numbers are first processed at a very output circuit then accepts this signal and converts it to an octal signal displayed on a readout device.must first be divided into groups of three，starting at the octal point.Each binary group is then converted into an equivalent octal number.These numbers are then combined，while remaining in their same respective places，to represent the equivalent octal number.3.2.4 Hexadecimal Number SystemThe digital systems to process large number values.The base of this system is 16，which means that the largest number used in a place is 15.Digits used by this system are the numbers 0-9 and the letters A-F. The letters A-P are used to denote the digits 10-15，respectively. The place values to the left of the .The process of changing a proper digital order.The place values，or powers of the base，are then positioned under the respective digits in step 2.In step 3，the value of each digit is recorded. The values in steps 2 and 3 are then multiplied together and added. The sum gives the decimal equivalent value of a . Initially，the converted to a binary number using four digits per group. The binary group is combined to form the equivalent binary number.The conversion of a decimal number to a ，as with other number systems. In this procedure the division is by 16 and remainders can be as large as 15.Converting a binary number to a groups of four digits，starting at the converted to a digital circuit-design applications binary signals arefar superior to those of the octal，decimal，or be processed very easily through electronic circuitry，since they can be represented by two stable states of operation. These states can be easily defined as on or off, 1 or 0，up or down，voltage or no voltage，right or left，or any other two-condition states. There must be no in-between state.The symbols used to define the operational state of a binary system are very important.In positive binary logic，the state of voltage，on，true，or a letter designation (such as A ) is used to denote the operational state 1 .No voltage，off，false，and the letter A are commonly used to denote the 0 condition. A circuit can be set to either state and will remain in that state until it is caused to change conditions.Any electronic device that can be set in one of two operational states or conditions by an outside signal is said to be bistable. Relays，lamps，switches，transistors, diodes and ICs may be used for this purpose. A bistable device .By using many of these devices，it is possible to build an electronic circuit that will make decisions based upon the applied input signals. The output of this circuit is a decision based upon the operational conditions of the input. Since the application of bistable devices in digital circuits makes logical decisions，they are commonly called binary logic circuits.If we were to draw a circuit diagram for such a system，including all the resistors，diodes，transistors and interconnections，we would face an overwhelming task, and an unnecessary one.Anyone who read the circuit diagram would in their mind group the components into standard circuits and think in terms of the" system" functions of the individual gates. Forthis reason，we design and draw digital circuit with standard logic symbols. Three basic circuits of this type are used to make simple logic decisions.These are the AND circuit, OR circuit, and the NOT circuit.Electronic circuits designed to perform logic functions are called gates.This term refers to the capability of a circuit to pass or block specific digital signals.The logic-gate symbols are shown in Fig.3-1.The small circle at the output of NOT gate indicates the inversion of the signal. Mathematically，this action is described as A=.Thus without the small circle，the rectangle would represent an amplifier (or buffer) with a gain of unity.An AND gate the 1 state simultaneously，then there will be a 1 at the output.The AND gate in Fig. 3-1 produces only a 1 out-put when A and B are both 1. Mathematically，this action is described as A·B=C. This expression shows the multiplication operation. An OR gate Fig.3-1 produces a when either or both inputs are l.Mathematically，this action is described as A+B=C. This expression shows OR addition. This gate is used to make logic decisions of whether or not a 1 appears at either input.An IF-THEN type of sentence is often used to describe the basic operation of a logic state.For example，if the inputs applied to an AND gate are all 1，then the output will be 1 .If a 1 is applied to any input of an OR gate，then the output will be 1 .If an input is applied to a NOT gate，then the output will be the opposite or inverse.The logic gate symbols in Fig. 3-1 show only the input and output connections. The actual gates，when wired into a digital circuit, would pin 14 and 7.3.4 Combination Logic GatesWhen a NOT gate is combined with an AND gate or an OR gate，it iscalled a combination logic gate. A NOT-AND gate is called a NAND gate，which is an inverted AND gate. Mathematically the operation of a NAND gate is A·B=. A combination NOT-OR ，or NOR，gate produces a negation of the OR function.Mathematically the operation of a NOR gate is A+B=.A 1 appears at the output only when A is 0 and B is 0.The logic symbols are shown in Fig. 3-3.The bar over C denotes the inversion，or negative function，of the gate.The logic gates discussed .In actual digital electronic applications，solid-state components are ordinarily used to accomplish gate functions.Boolean algebra is a special form of algebra that was designed to show the relationships of logic operations.Thin form of algebra is ideally suited for analysis and design of binary logic systems.Through the use of Boolean algebra，it is possible to write mathematical expressions that describe specific logic functions.Boolean expressions are more meaningful than complex word statements or or elaborate truth tables.The laws that apply to Boolean algebra are used to simplify complex expressions. Through this type of operation it may be possible to reduce the number of logic gates needed to achieve a specific function before the circuits are designed.In Boolean algebra the variables of an equation are assigned by letters of the alphabet.Each variable then exists in states of 1 or 0 according to its condition.The 1，or true state，is normally represented by a single letter such as A，B or C.The opposite state or condition is then described as 0，or false，and is represented by or A’.This is described as NOT A，A negated，or A complemented.Boolean algebra is somewhat different from conventional algebra withrespect to mathematical operations.The Boolean operations are expressed as follows:Multiplication:A AND B，AB，,A·BOR addition:A OR B .A+BNegation，or complementing:NOT A，，A’Assume that a digital logic circuit only C is on by itself or when A，B and C are all on expression describes the desired output. Eight (23) different combinations of A，B，and C exist in this expression because there are three，inputs. Only two of those combinations should cause a signal that will actuate the output. When a variable is not on (0)，it is expressed as a negated letter. The original statement is expressed as follows: With A，B，and C on or with A off, B off, and C on ，an output (X）will occur:ABC+C=XA truth table illustrates if this expression is achieved or not.Table 3-1 shows a truth table for this equation. First，ABC is determined by multiplying the three inputs together.A 1 appears only when the A，B，and C inputs are all 1.Next the negated inputs A andB are determined.Then the products of inputs C，A，and B are listed.The next column shows the addition of ABC and C.The output of this equation shows that output 1 is produced only when C is 1 or when ABC is 1.A logic circuit to accomplish this Boolean expression is shown in Fig. 3-4.Initially the equation is analyzed to determine its primary operational function.Step1 shows the original equation.The primary function is addition，since it influences all parts of the equation in some way.Step 2 shows the primary function changed to a logic gate diagram.Step 3 showsthe branch parts of the equation expressed by logic diagram，with AND gates used to combine terms.Step 4 completes the process by connecting all inputs together.The circles at inputs，of the lower AND gate are used to achieve the negative function of these branch parts.The general rules for changing a Boolean equation into a logic circuit diagram are very similar to those outlined.Initially the original equation must be analyzed for its primary mathematical function.This is then changed into a gate diagram that is inputted by branch parts of the equation.Each branch operation is then analyzed and expressed in gate form.The process continues until all branches are completely expressed in diagram formmon inputs are then connected together.3.5 Timing and Storage ElementsDigital electronics involves a number of items that are not classified as gates.Circuits or devices of this type the operation of a system.Included in this system are such things as timing devices，storage elements，counters，decoders，memory，and registers.Truth tables symbols，operational characteristics，and applications of these items will be presented an IC chip. The internal construction of the chip cannot be effectively altered. Operation is controlled by the application of an external signal to the input. As a rule，very little work can be done to control operation other than altering the input signal.The logic circuits in Fig. 3-4 are combinational circuit because the output responds immediately to the inputs and there is no memory. When memory is a part of a logic circuit，the system is called sequential circuit because its output depends on the input plus its an input signal isapplied.A bistable multivibrator，in the strict sense，is a flip-flop. When it is turned on，it assumes a particular operational state. It does not change states until the input is altered.A flip-flop opposite polarity.Two inputs are usually needed to alter the state of a flip-flop. A variety of names are used for the inputs.These vary a great deal between different flip-flops.1. R-S flip-flopsFig.3-5 shows logic circuit construction of an R-S flip-flop. It is constructed from two NAND gates. The output of each NAND provides one of the inputs for the other NAND. R stands for the reset input and S represents the set input.The truth table and logic symbol are shown in Fig. 3-6.Notice that the truth table is somewhat more complex than that of a gate. It shows, for example，the applied input, previous output，and resulting output.To understand the operation of an R-S flip-flop，we must first look at the previous outputs.This is the status of the output before a change is applied to the input. The first four items of the previous outputs are Q=1 and =0. The second four states this case of the input to NANDS is 0 and that is 0，which implies that both inputs to NANDR are 1.By symmetry，the logic circuit will also stable with Q0 and 1.If now R momentarily becomes 0，the output of NANDR，，will rise to resulting in NANDS be realized by a 0 at S.The outputs Q and are unpredictable when the inputs R and S are 0 states.This case is not allowed.Seldom would individual gates be used to construct a flip-flop，rather than one of the special types for the flip-flop packages on a single chipwould be used by a designer.A variety of different flip-flops are used in digital electronic systems today. In general，each flip-flop type R-S-T flip-flop for example .is a triggered R-S flip-flop. It will not change states when the R and S inputs assume a value until a trigger pulse is applied. This would permit a large number of flip-flops to change states all at the same time. Fig. 3-7 shows the logic circuit construction. The truth table and logic symbol are shown in Fig. 3-8. The R and S input are thus active when the signal at the gate input (T) is 1 .Normally，such timing，or synchronizing，signals are distributed throughout a digital system by clock pulses，as shown in Fig. 3-9.The symmetrical clock signal provides two times each period.The circuit can be designed to trigger at the leading or trailing edge of the clock. The logic symbols for edge trigger flip-flops are shown in Fig.3-10.2. J-K flip-flopsAnother very important flip-flop unpredictable output state. The J and K inputs addition to this，J-K flip-flops may employ preset and preclear functions. This is used to establish sequential timing operations. Fig.3-11 shows the logic symbol and truth table of a J-K flip-flop.3. 5. 2 CountersA flip-flop be used in switching operations，and it can count pulses.A series of interconnected flip-flops is generally called a register.Each register can store one binary digit or bit of data. Several flip-flops connected form a counter. Counting is a fundamental digital electronic function.For an electronic circuit to count，a number of things must beachieved. Basically，the circuit must be supplied with some form of data or information that is suitable for processing. Typically，electrical pulses that turn on and off are applied to the input of a counter. These pulses must initiate a state change in the circuit when they are received. The circuit must also be able to recognize where it is in counting sequence at any particular time. This requires some form of memory. The counter must also be able to respond to the next number in the sequence. In digital electronic systems flip-flops are primarily used to achieve counting. This type of device is capable of changing states when a pulse is applied，output pulse.There are several types of counters used in digital circuitry today.Probably the most common of these is the binary counter.This particular counter is designed to process two-state or binary information. J-K flip-flops are commonly used in binary counters.Refer now to the single J-K flip-flop of Fig. 3-11 .In its toggle state，this flip-flop is capable of achieving counting. First，assume that the flip-flop is in its reset state. This would cause Q to be 0 and Q to be 1 .Normally，we are concerned only with Q output in counting operations. The flip-flop is now connected for operation in the toggle mode. J and K must both be made the 1 state. When a pulse is applied to the T，or clock，input，Q changes to 1.This means that with one pulse applied，a 1 is generated in the output. The flip-flop the next pulse arrives，Q resets，or changes to 0. Essentially，this means that two input pulses produce only one output pulse. This is a divide-by-two function.For binary numbers，counting is achieved by a number of divide-by-two flip-flops.To count more than one pulse，additional flip-flops must be employed. For each flip-flop added to the counter，its capacity is increased by the power of 2. With one flip-flop the maximum count was 20，or 1 .For two flip-flops it would count two places，such as 20 and 21.This would reach a count of 3 or a binary number of 11.The count would be 00，01，10，and 11. The counter would then clear and return to 00. In effect, this counts four state changes. Three flip-flops would count three places，or 20，21，and 22.This would permit a total count of eight state changes.The binary values are 000，001，010，011，100，101，110 and 111.The maximum count is seven，or 111 .Four flip-flops would count four places，or 20，21，22，and 23.The total count would make 16 state changes. The maximum count would be 15，or the binary number 1111.Each additional flip-flop would cause this to increase one binary place.河南理工大学电气工程及其自动化专业中英双语对照翻译。

电气专业毕业设计外文翻译--防雷接地

Lightning protection groundingAbstract The significance of lightning p.rotection and mitigation on very little money to prevent large losses, and its function is to use scientific means avoid natural disasters. Grounding is to make the system has been included in the lightning protection lightning energy discharge into the earth, and good grounding can effectively reduce the online guide overvoltage, avoid counterattack. Avoid ground is the most important aspect of technology, whether sings rem, induction lightning, or other forms of ray, ultimately the lightning current into the earth. Therefore, no reasonable and good grounding device is can't reliably the lightning strikes. The smaller the grounding resistance, come loose flow is quicker, lightning objects the time to maintain high potential more short, the less riskKey W ords:Lightning protection; Grounding; Current; potential1 introductionIn recent years, many domestic and foreign standards do not advocate information equipment using independent grounding device, recommend the use of common earthing system. For example, the 2000 edition of the GB50057-94" design code for protection of structures" in point out clearly:" every building itself should adopt common earthing system" to be the buildings within the various grounding are unified to buildings based on, or outdoor grounding device. When the building was hit by lightning, power system voltage and electrical equipment grounding voltage rises at the same time, keep the equipment working voltage constant, so that the electronic equipment from lightning strikes can work normally. Common earthing system usually use the building foundation grounding electrode, the grounding resistance less than 1 ohm in general, if the equipment grounding resistance requirement is lower, should take the minimum value.The ground that has been incorporated into the lightning protection system of lightning energy drain into the earth, good grounding downlead to effectively reduce the voltage on the back, to avoid the occurrence of. In the past some requirements of electro nic equipment grounding alone, the purpose is to prevent stray current and transient current in power network disturbance of the normal work of equipment. Before 90 time, forces of the communication navigation equipment electronic tube device, using analog communication mode, analog communication on particularly sensitive to interference, interference, so will take power and communications grounding separate way. Now, the lightning protection engineering fields do not advocate a separate ground. In the IEC standards and ITU standards are not advocating a separate ground, American Standard IEEEStd1100-1992more sharply pointed out: not recommended the use of any kind of so-called separate, independent,computer, electronic or other such incorrect ground as equipment grounding conductor of a connection point. Grounding is the most fundamental aspect of the lightning protection system. The ground is not good, all the measures of lightning protection effect can play. Lightning protection grounding is ground communication stationCode for construction and acceptance of the basic safety requirements, the grounding of PLC belongs to a low-voltage electrical equipment of single point grounding modeLow voltage electrical equipment of single point grounding mode can be divided into: tandem type single point grounding, parallel type single point grounding, multiple branching of single point grounding.2 single point grounding methodTandem type single point grounding: or first grounding ways. Method : the number of low voltage electrical equipment grounding terminal equipment with the same root near the ground wire connecting, then through this grounding and grounding device. The grounding system is: save manpower, material resources; while the disadvantage is that: when the public grounding line open circuit, if the grounding system has a device leakage, can cause other equipment which occurred on voltage, a threat to the safety of personnel.B ackup ground terminal introducing a grounding line, and then the number of lines at the same time received a grounding device. The grounding system is: when the grounding system in which a device grounding wire broken circuit, will not cause other equipment enclosure voltage, to ensure personal safety. This grounding mode is: if it is not perfect on the interference of high frequency electronic equipment or other highly sensitive electrical equipment, high frequency interference from other devices ( such as converter, intermediate frequency stove thyristor converter parts) will be from the common place of string, causing the device is not working properly.Multiple branching of single point grounding: or third grounding ways. Grounding method: each equipment grounding terminal alone received a grounding device. Earthing method and second kinds of grounding is the difference: the device has a separate grounding body ( or a change of: received directly from the grounding body recent grounding device ( or grounded source office ), each device in the electrical ground loop on the distance is far more (for example, more than 50meters ) ). This effectively avoids the mutual electrical equipmentMagnetic interference.But this grounding mode time-consuming, laborious and separate grounding the source is not good for.In the usual construction, in fact the grounding of PLC way adopts the second grounding ways, as for electromagnetic interference: if the cabinet is provided with a plurality of high power frequency converter, can be in the PLC power supply is installed in front of a single-phase power filter can be, generally designed in the inverter PLC near the front end are equipped with power supply filter.The interference effect of DC and AC equipment, can be connected together -- even if the DC and AC circuits because of some reason connectivity, because they are not the same as a loop ( grounding is not part of the loop ), will not cause damage to the equipment. People have AC220V power and DC24V circuit connected to it, but the equipment work remains normal.Digital and analog ground suggested separately ( unless you're a low-voltage electrical equipment power supply voltage only a few tens of volts ), because the digital circuit belongs to positive and negative 5V,12V,24V level, are vulnerable to interference, and once the external abnormal voltage once the series will very possible equipment damage. I just go to work in the factory has a 1000 tons of SACMI press, because other equipment and digital ground causes the electronic facilities burned down last several times, Italy sent technicians ( just graduated from secondary school students ) and replacement equipment, conductor of the in situ dug a pit, buried a piece of ground the brass and the earthing filler, engage in a separate grounding.3 Lightning proof grounding device for part of a concept(1) Lightning receiving device directly or indirectly accept the lightning rod ( flash ), such as lightning, lightning protection zone ( net ), overhead ground wire and arrester. (2) lead: for the lightning current from the lightning arrester is conducted to the grounding conductor.(3) grounding: electrical equipment, tower grounding terminal and a grounding body or the zero line connected with the normally not current-carrying metal conductor.(4) grounding body ( polar ): buried in the soil and directly touch the earth metal conductor, known as the grounding body. Divided into vertical grounding electrode and level of grounding body.(5): grounding device grounding and grounding. (6): grounding grid by vertical and horizontal grounding body composition having discharge and pressure equalizing function network grounding device. (7): grounding resistance of grounding body or natural grounding resistance to the ground of the sum, a grounding device resistance, its value is equal to the grounding device of voltage to the ground and through the grounding body into ground current ratio. At the same time the grounding resistance of grounding device is a constant level indication.4 The grounding device is easy to corrosion location mainly(1) equipment grounding downlead and connecting screws; (2) each welding head; (3) cable channel equalizing zone; (4) the horizontal grounding body,Anti corrosion measures,grounding body using copper, copper clad steel earth body or hot galvanized materials; welding brush asphalt paint or powder coating; use of cathodic protection.One, ground resistance test requirements: a. AC grounding, grounding resistance should be less than4 ohm; b. Safety grounding, grounding resistance should be less than4 ohm; C DC grounding, grounding resistance should be according to the computer system specific requirements determined; lightning protection to D. Grounding resistance should be less than10 ohm; e for shielding system if the joint grounding, grounding resistance should not be greater than1 ohms.Two, ground resistance tester ZC-8grounding resistance meter is used for measuring the power system, electrical equipment, lightning and grounding resistance value. Also measuring low resistance conductor resistance and resistivity of soil.In three, the instrument by hand generator, current transformer, a slide wire resistor and galvanometer etc., all arranged in the plastic shell body, and the shell is convenient for carrying. Accessory auxiliary probe wires, installed in the accessory bag.The working principle of the voltage comparing type.I n four, before use to check whether the complete tester, tester comprises the following device. In 1, ZC-8 type grounding resistance tester, a2auxiliary grounding rods two root of 3,5m,20m,40m wire aGround resistance tester, usually hand ZC-XX series, including a short black lines, a20M line, a40M line, testing line connected at one end of a tested object whose the other end is connected with a shake table on each of two short connecting terminals, and the remaining 2terminal 20M line with P terminal,40M line C terminal to terminal, after the 20M and 40M line according to the ribbon (that is, to shake table for the endpoint of a triangle ) or linear completely out, hit good probe. In the shake table select file and then to 120RPM speed swing table, side table edge with a shake shake table can dial0, until the pointer on a shake table center scale 0, with stalls multiplied by the dial corresponding numerical result this grounding grounding resistance.Wire grounding is an important electrical safety technical measures, the operation should be serious, serious, comply with the requirements of technical specifications, must not be careless. Therefore, correctly use the ground, normative hanging, remove grounding behavior, consciously cultivate rigorous safety work style, improve their awareness of safety, to resistthe danger from thousands of miles away, in order to avoid the ground causes electrical accident.A ccording to the practical work, ground use should pay attention to the following matters.1work must be checked before grounding wire. Soft copper wire is broken, the screw loose connections, hook line stretch is normal, do not meet the requirements should be replaced or repaired before use.2 hanging wire must be a priori power, not checking cable grounding is the base of common habitual violations, in suspension when the grounding body and physical contact.3 in the work place two segment ends hanging earthing, lest the user would send electric, induction electricity, suffer a number of examples.4 in the play ground pile, you should dial can borrow to physical fast dredge accident current, grounding the quality guarantee.5to protect the earth. Grounding wire in use in the process may not be twisted, should not soft copper wire wheel, grounding in removed, not from the air leaving or anywhere to fall, use rope transfer, pay attention to ground cleaning work.6new staff must go through ground wire using the training, learning, after passing the examination, can the individual engaged in ground operation or use of the work.According to the different voltage levels corresponding to7specifications of the grounding wire selection.8prohibited the use of other metal wire instead of grounding wire.The 9 grounding wire has two sides, it has a safety function, improper use will produce destructive effect, so after work to timely removal of ground wire. With the earthing switch may damage electrical equipment and the destruction of the power grid stability, can lead to severe malignant electric accident.10field work not less hanging earthing conductor or alter the articulated ground location.5 Lightning protection system construction methods and technical measuresLightning protection system grounding engineering major required close coordination, interspersed with civil completed. In civil unit beam, column and reinforced structure modeling is to follow up the grounding body ( line ) of the lap welding and grounding lead welding. In order to prevent the welding fault leakage, during each lightning protection on the ground ( body ) after welding, are on the main reinforcement is painted in eye-catching mark, for the benefit of a layer.Wire, mesh welding.Lightning protection construction methodAccording to the design institute to provide the drawings, using the foundation steel (including pile steel mesh cage bars ) as the lightning protection and grounding, using column within 2main bar as lead, using concrete foundation beam reinforced bar as electrode connection, use of roof beam reinforcing steel bar and reinforced parapet coping as dark installed lightning protection belt.Flank-Striking lightning protection construction method:1straight buried metal pipes and metal top and lightning protection device.2into the building of buried metal pipeline, roof all the metal pipeline and its structure also and lightning protection device.3note that in the construction of grounding body ( line ) of the lap length must comply with the following provisions:3.1flat to2 times its width ( and at least 3edge welding);3.2bar is connected by double lapped continuous welding of , weld length not less than 6 times the diameter, good weld appearance;3.3round steel and flat steel connections, its length is6 times the diameter of round steel;3.4flat steel and steel, flat steel and angle steel welding, in order to reliable connection, except in the contact area on both sides of the welding, and welding to steel bent into arc ( or angle ) clips or directly by the strip itself curved surface arc ( or angle ) and steel ( or angle ) welding.3.5 exposed lightning strip galvanized special clamping support code support, avoid the support member and lightning belt welding.3.6steel pipe for lightning protection grounding device (including needle, etc. ), tube wall thickness not less than2.5mm. The butt welding of the tube, pipe is provided suitable liner pipe diameter. And connecting pipe diameter dovetails, lining length not less than4 times the outside diameter.From3.7in the first layer of ground1.51.8m leads to easy operation and maintenance of the permanent test. Test points are obvious grounding mark and reliable and anti-corrosion measures.The 3.8grounding resistance should be performed to detect, plus or minus 0part test point were tested individually, + 0above part can use test point of each of the three layer is a detection, i.e. each completed a lightning arrester grading ring or band is installed you can use e lectrode leading-out wire of a test work. The grounding resistance measurement requirements of less than 1ohm.6 Lightning protection engineering construction quality defects and Its CountermeasuresRoofing exposed metal pipe and equipment and component without lightning protection connection, or the connection does not meet the requirements, there is the potential for harm of thunder and lightning.Construction countermeasures:1strictly implement the" design code for protection of structures" ( GB5005794) concerned regulation, ensure the impulse grounding resistance to meet the requirements.The 2connecting leads not directly in galvanized steel pipe welding, suitable for welding or bolt connection in the special grounding wire card ( or metal pipe bracket ).The 3lightning protection connection lead should be concealed, grounding bar welding not fusion, resulting in effective contact area is reduced, the lightning will fuse risk.Construction countermeasures:Construction should pay attention to the appropriate electrode angle, swing, pay attention to the melting of lap joints on both sides.,Earthing and equipotential connection:1 all electrical equipment metal shell, frame, line pipe, cable bridge must have good ground, make it a good grounding path.2used for outdoor grounding bar welding length not less than 6times the diameter of round steel, flat steel two surface welding; the connection between the flat width for2 times, three surface welding; round steel and flat steel bar connection for6 times, two surface welding.3potential galvanized round steel welded beam in foundation of the main grounding bar, and small ground lines are connected, in the connection equipotential box galvanized plate, welding seam must be full. Indoor draught to the equipotential box is connected with the circuit to be connected is complete, the grounding wire specifications of not less than 4mm2, and ensure reliable contact.4 ground connection of all welds must oil antirust paint two times ( with the exception of concrete structure welding ); galvanized grounding bar, flat steel in the underground buried depth should not be less than0.8m.7 Importance of grounding and lightning grounding resistance testingLightning protection and grounding technology,In order to solve the communication network (including the user terminal ) overvoltage protection for the purpose, has developed a variety of lightning protection and grounding technology, these are to ensure the reliability of telecommunication network technology, is the important basic technology in the field of communication. Now commonly used by telecommunications building integrated earthing( grounding ) and introduces a variety of lightning protection device. But, now has access to the optical fiber communication era, even in the communication network of the user terminal, at the same time, and connected to an AC power line, at the user terminal using the large scale integrated circuit is more and more, the new features of the lightning protection and grounding, raised new requirement, we must try to adapt to these new characteristics.Grounding resistance test technology.In recent years, because of digital technology and the development of optical communication technology, so that the original installation in a telephone exchange part of the exchange, transmission equipment to the user mobile, and often these devices are mounted to the general residential buildings and overhead, so ask them with the telephone exchange room floor with.The shielding effect, it is obviously not possible, then how to do? Now hand requires these devices improve the adaptability, on the other hand, in order to prevent the leakage of electricity and lightning voltage on human body and equipment hazards, gro unding and lightning protection is vital.From the grounding purposes, especially for outdoor equipment grounding, leakage current and lightning protection is particularly important. The grounding resistance requirements, technical standards are clearly defined, it is. In order to ensure that the grounding resistance value to meet the requirement, after construction of the grounding resistance testing work is very necessary. But with the progress of the modernization of city, now the city roads and sidewalks are all concrete pavement asphalt pavement or covered now, if still use auxiliary electrode method to test the ground resistance, it is difficult to too much. The new ground resistance test method are introduced.In 1, the existing ground resistance test method.Wire grounding resistance is equal to the grounding electrode potential and the injected current ratio. The current earth resistance test method, as shown in figure 1. Where E is the grounding electrode, C is injected into the current of the auxiliary electrode, P is to test the potential of the auxiliary electrode imaginary reference point. Test, signal device in the E ~ C electrode with500 ~ 2KHz AC current by the dotted line into a flow, a current meter and a voltage meter readings, we can find the grounding resistance value.In order to test the value of accurate, the distance between the electrodes shall be not less than 10meters. The distance, in the downtown area of the city, is often difficult to do.防雷接地摘要防雷减灾的意义在于用很少的钱预防大的损失，其作用在于使用科学的手段规避自然灾害。

电气专业毕业设计外文翻译--电源管理技术及计算

附录3 英文资料Power Management Techniques and CalculationRelevant DevicesThis application note applies to the following devices: C8051F000, C8051F001, C8051F002, C8051F005, C8051F006, C8051F010, C8051F011, C8051F012, C8051F012, C8051F015, C8051F016, and C8051F017.IntroductionThis application note discusses power management techniques and methods of calculating power in a Cygnet C8051F00x and C8051F01x Sock. Many applications will have strict power requirements, and there are several methods of lowering the rate of power consumption without sacrificing performance. Calculating the predicted power use is important to characterize the system‟s power supply requirements.Key Points• Supply volt age and system clock frequency strongly affect power consumption.• Cygnet‟s Sock‟s feature power management modes: IDLE and STOP.• Power use can be calculated as a function of system clock frequency, supply voltage, and enabled peripherals.Power Saving MethodsCMOS digital logic device power consumption is affected by supply voltage and system clock (SYSCLK) frequency. These parameters can be adjusted to realize power savings, and are readily controlled by the designer. This section discusses these parameters and how they affect power usage.Reducing System Clock FrequencyIn CMOS digital logic devices, power consumption is directly proportional to system clock (SYSCLK) frequency: power=CV2ƒ, where C is CMOS load capacitance, V is supply voltage, and ƒ is SYSCLK frequency.Equation 1.CMOS Power EquationThe system clock on the C8051Fxxx family of devices can be derived from an internal oscillator or an external source. External sources may be a CMOS clock, RC circuit, capacitor, or crystal oscillator. For information on configuring oscillators, see applic ation note: “AN02 - Configuring the Internal and External Oscillators.” The internal oscillator can provide four SYSCLK frequencies: 2, 4, 8, and16 MHz. Manydifferent frequencies can be achieved using the external oscillator.To conserve power, a designer must decide what the fastest needed SYSCLK frequency and required accuracy is for a given application. A design may require a constant SYSCLK frequency during all device opera tions. In this case, the designer will choose the lowest possible frequency required, and use the oscillator configuration that consumes the least power. Typical applications include serial communications, and periodic sampling with an ADC that must be performed.Some operations may require high speed operation, but only in short, intermittent intervals. This is sometimes referred to as “burst” operation. In the C8051Fxxx, the SYSCLK frequency can be changed at anytime. Thus, the device can operate at low frequency until a condition occurs that requires high frequency operation.Two examples of alternating between SYSCLK sources are (1) an internal oscillator/external crystal configuration, and (2) an external crystal/RC oscillator configuration. If the device is used for occasional high speed data conversion, and a real-time clock is used for time-stamping the data, a combination internal oscillator and external crystal would be ideal. During sampling operations, the high speed internal oscillator would be used. When sampling is complete, the device could then use an external 32 kHz crystal to maintain the real-time clock. Once high speed operations are required again, the device switches to the internal oscillator as necessary (see Figure 1below). An example of this procedure is illustrated in application note “AN008 Implementing a Rea l-Time Clock”.The crystal oscillator and internal oscillator may be operated simultaneously and each selected as the SYSCLK source in software as desired. To reduce supply current, the crystal may also be shutdown when using the internal oscillator. In this case, when switching from the internal to external oscillator the designer must consider the start-up delay when switching the SYSCLK source. The C8051F0xx devices have a flag that is set when the external clock signal is valid (XTLVLD bit in the OSCXCN register) to indicate the oscillator is running and stable. This flag is polled before switching to the external oscillator. Note that other operations can continue using the internal oscillator during the crystal start-up time.Some applications require intermittent high speed and accuracy (e.g., ADC sampling and data processing), but have lower frequency and accuracy requirements at other times (e.g., waiting for sampling interval), a combination of an external oscillator and RC circuit can be useful. In this case, the external RC oscillator is usedto derive the lower frequency SYSCLK source, and the crystal is used for high frequency operations. The RC circuit requires a connection to VDD (voltage source) to operate.Because this connection could load the crystal oscillator circuit while the crystal is in operation, we connect the RC circuit to a general purpose port pin (see Figure 2 below). When the RC circuit is in use, the port pin connection is driven high (to VDD) by selectin g its output mode to “push-pull” and writing a …1‟ to the port latch. When the crystal oscillator is being used, the port pin is placed in a …hi- Z‟ condition by configuring the output mode of the port to “open-drain” and writing a …1‟ to the port latch. Note the RC circuit may take advantage of the existing capacitors used for the crystal oscillator.The start-up of the RC-circuit oscillator is nearly instantaneous. However, there is a notable start-up time for the crystal. Therefore, switching from the RC oscillator to the external crystal oscillator using the following procedure:1. Switch to the internal oscillator.2. Configure the port pin used for the RC circuit voltage supply as open-drain and write a …1‟ to the port pin (Hi-Z condition).3. Start the crystal (Set the XFCN bits).4. Wait for 1 ms.5. Poll for the External Crystal Valid Bit (XTLVLD --> …1‟).6. Switch to the external oscillator.Switch from the external crystal oscillator to the RC oscillator as follows:1. Switch to the internal oscillator.2. Shutdown the crystal (clear the XFCN bits).3. Drive the voltage supply port pin high (to VDD) by putting the port pin in“push pull” mode and writing a …1‟ to its port latch.4. Switch back to the external oscillator.Supply VoltageThe amount of current used in CMOS logic is directly proportional to the voltage of the power supply. The power consumed by CMOS logic is proportional the power supply voltage squared (See Equation 1). Thus, power consumption may be reduced by lowering the supply voltage to the device. The C8051Fxxx families of devices require a supply voltage of 2.7-3.6 Volts. Thus, to save power, it is recommended to use a 3.0 volt regulator instead of a 3.3 volt regulator for power savings.CIP-51 Processor Power Management Mode sThe C8051 processor has two modes which can be used for power management. These modes are IDLE and STOP.IDLE ModeIn IDLE Mode, the CPU and FLASH memory are taken off-line. All peripherals external to the CPU remain active, including the internal clocks. The CPU exits IDLE Mode when an enabled interrupt or reset occurs. The CPU is placed in IDLE Mode by setting the Idle Mode Select Bit (PCON.0) to …1‟.When the IDLE Mode Select Bit is set to …1‟, the CPU enters IDLE Mode once the instruction that sets the bit has executed. An asserted interrupt will clear the IDLE Mode Select Bit and the CPU will vector to service the interrupt. After a return from interrupt (RETI), the CPU will return to the next instruction following the one that had set the IDLE Mode Select Bit. If a reset occurs while in IDLE Mode, the normal reset sequence will occur and the CPU will begin executing code at memory location 0x0000.As an example, the CPU can be placed in IDLE while waiting for a Timer 2 overflow toInitiate a sample/conversion in the ADC. Once the conversion and sample processing is complete, the ADC end-of-conversion interrupt wakes the CPU from IDLE Mode and processes the sample. After the sample processing is complete, the CPU is placed back into IDLE Mode to save power while waiting for the next interrupt.As another example, the CPU may wait in IDLE Mode to save power until an externalInterrupt signal is used to “wake up” the CPU as needed. Upon receivin g an external interrupt, the CPU will exit IDLE Mode and vector to the corresponding interrupt vector (e.g., / INT0 or /INT1).STOP ModeThe C8051 STOP Mode is used to shut down the CPU and oscillators. This will effectively shut down all digital peripherals as well. All analog peripherals must be shutdown by software prior to entering STOP Mode. The processor exits STOP Mode only by an internal or external reset. Thus, STOP Mode saves power by reducing the SYSCLK frequency to zero.Note that the Missing Clock Detector will cause an internal reset (if enabled) that will terminate STOP Mode. Thus, the Missing Clock Detector should be disabled prior to entering STOP Mode if the CPU is to be in STOP Mode longer than the Missing Clock Detector timeout (100 μs).The C8051 processor is placed in STOP Mode by setting the STOP Mode Select Bit (PCON.1) to …1‟. Upon reset, the CPU performs the normal reset sequence and begins executing code at 0x0000. Any valid RESET source will exit STOP Mode. Sources of reset to exit STOP Mode are External Reset (/RST), Missing Clock Detector, Comparator 0, and the External ADC Convert Start (/CNVSTR).As an example, the CPU may be placed in STOP Mode for a period to save power when no device operation is required. When the device is needed, Comparator 0 reset could be used to “wake up” the device.Generally, a power conscious design will use the lowest voltage supply, lowest SYSCLK frequency, and will use Power Management Modes when possible to maximize power savings. Most of these can be implemented or controlled in software.Calculating Power ConsumptionThere are two components of power consumption in Cygnet‟s C8051F00x and C8051F01x family of devices: analog and digital. The analog component of power consumption is nearly constant for all SYSCLK frequencies. The digital component of power consumption changes considerably with SYSCLK frequency. The digital and analog components are added to determine the total power consumption.The current use calculations presented in this application note apply to the C8051F00x and C8051F01x (…F000, 01, 02, 03, 05, 06, 10, 11, 12, 15, and 16) family of Cygnet devices.The data sheet section, “Global DC Electrical Characteristics” contains various supply current values for different device conditions. The current values are separated into digital (at three example frequencies) and analog components. The analog numbers presented are values with all analog peripherals active. Supply current values for each analog peripheral can be found in the data sheet section for the peripheral.For convenience, the Global DC Electrical Characteristics for the C8051F00x and C8051F01x family of devices are presented in the table below.Internal vs. External OscillatorBesides using lower SYSCLK frequencies, the designer can realize power savings by making smart SYSCLK source choices. The internal oscillator will typically consume 200μA of current supplied from the digital power supply. The current used to drive an external oscillator can vary. The drive current (supplied from the analog power supply) for an external source, such as a crystal, is set in software by configuring the XFCN bits in the External Oscillator Control Register (OSCXCN). Thus, at higher drive currents the user may save power by using the internal oscillator. However, at the lowest XFCN setting the external oscillator will use less than 1μA which is less current than used by the internal oscillator. Some typical measured current values are listed below. These measurements may vary from device to device. This drive level is kept as low as possibleTo minimize power consumption, but must be high enough to start the external oscillator. The following table lists the current vs. External Oscillator Frequency Control Bit settings.Digital PeripheralsFor rough calculations, a good rule of thumb is to assume a 1mA/MHz of operating current (digital) + 1mA if the analog components (ADC, comparators, DAC, VREF, etc.) are enabled. This rule of thumb assumes a 3.6 V supply voltage. A lowersupply voltage will reduce power consumption. At 2.7 V, the rule of thumb is 0.5mA/MHz (in NORMAL mode). The rules of thumb for rough calculations are presented in the table below:Analog PeripheralsThe individual supply current values for each analog peripheral are posted in the data sheet section for that component (typically near the end of the section). It is recommended to disable all peripherals not in use to save power. For convenience, the C8051F00x and C8051F10x analog peripherals supply current values are listed below:Calculating Total CurrentWhen the required SYSCLK frequency, supply voltage, and peripherals have been determined, the total supply current can be estimated. To calculate the total supply current, the analog peripheral current use (found by adding the currents of each of the enabled analog peripherals) is added to the digital current use (calculated for a given frequency, power mode, and supply voltage). If all of the analog peripherals are enabled, analog current use is about 1mA.Example CalculationsThe following are examples of supply current calculations. Each application may use different power modes, SYSCLK frequencies, and peripherals at different times. Thus, power management specifications may require several different supply current calculations. The digital component and analog components of current use are found separately, and then added together for the total.Example 1The C8051F000 device is being used in a system with VDD=3.6 V. An ADC is sampling parameters and processing the sample for an output to one DAC. Because of the sampling and processing requirements of the application, SYSCLK frequency is 16 MHz using the internal oscillator.Analog ComponentsPeripheral Supply Current (μ A)ADC 450VREF (internal) 50Internal Oscan. 200One DAC 110VDD monitor 15Total Analog 825Digital ComponentIn NORMAL Mode @ 16 MHz;1mA/M Hz * 16 MHz = 16mATotal825μA (analog) + 16mA (digital)= 16.8mAExample 2Assume we are still estimating the supply current in the same application in Example 1. If the sample processing is a burst operation (i.e., intermittent need for sampling and conversions), we may choose to place the CIP-51 in IDLE Mode to allow a Timer to wake-up the CIP-51 after a specified interval. In this case, the average supply current can be calculated in order to estimate power requirements. The device will switch between NORMAL Mode (for sampling and data conversion) and IDLE Mode (between sample processing operations). The switch between IDLE and NORMAL Modes (and supply current values) will happen in a cycle with a period equal to the sampling rate. (See Figure 3 below). This will allow us to calculate average supply current, after we calculate the supply current in IDLE Mode.Analog ComponentAnalog peripherals are disabled during the IDLE Mode period between sample processing and output. Thus, analog current consumption is just:VDD monitor = 15μA.Digital ComponentIn IDLE Mode @ 16 MHz;0.65mA/MHz * 16 MHz = 10.4mATotalThe analog component would be considered negligible in most applications, thus, the total is just the digital component:50μA (analog) + 10.4mA (digital) = 10.4mANow that we have calculated IDLE Mode supply current and NORMAL Mode supply current (in Example 1), we must calculate the time we spend in each mode to find the average current the device will use.Assuming the ADC is in low-power tracking mode and at the maximum SAR conversionClock of 2 MHz (ADC set for SAR clock = SYSCLK/8), and we desire a 10 kHzsampling rate. The period of the power cycle in Figure 3 is 1/10,000 (sample rate) = 100μs.The time in NORMAL Mode will be the ADC tracking/conversion time, and the time to store the value in memory. In low-power tracking mode, it will take 3 SAR clocks for tracking, and 16 SAR clocks for conversion. 19 SAR clocks at 2 MHz will take 9.5μs. To store the number will take to system clock cycles, or 0.125μs. To enter NORMAL Mode, a move instruction is executed, taking 3 SYSCLK cycles which takes 0.188μs. Thus, the total time in NORMAL Mode is 9.5 μs+0.125 μs+0.188μs = 9.8μs.Because the ADC sample period is 100μs, the time we may be in IDLE Mode during the power cycle is 100μs - 9.8μs (time in NORMAL Mode) = 90.2μs. By integrating the area under the curve in Figure 3 for one period (100μs), and dividing that number by the period, the average supply current is 11mA.Example 3If the oscillator frequency were lowered while in IDLE Mode (in Example 2) to 32 kHz using an external crystal for additional power savings, the current use would be:The external oscillator contr ol bits will be set to XFCN = 000. This uses 0.6μA of analog current. (0.65mA *.032 MHz) + 0.6μA = 21μAThis is a dramatic difference from Example 2‟s IDLE Mode at 16 MHz, by simply reducing oscillator frequency.Continuing with the average supply current calculation in Example 2 (with 6 extra SYSCLK cycles in NORMAL Mode to lower the frequency), the average supply current would be 1.7mA!Example 4In this application, the C8051F000 is being used to sample a parameter using the ADC and store samples in memory, with high accuracy timing of samples required. For more accurate timing, the SYSCLK is derived from an external 18.432 MHz crystal oscillator. To save power, the designer has decided to use a supply voltage of 3.0 V. Timer 2 is used to time the ADC sampling intervals.Digital ComponentIn NORMAL Mode @ 18.432 MHz;0.8mA/MHz * 18.432 MHz = 14.7mATotal Current Use3.4mA (analog)+14.7mA (digital)= 18.1mAExample 4 in IDLE ModePlacing the application in IDLE Mode with the ADC disabled during intervals that sampling is not required (no CIP-51 operations are needed; digital peripherals continue to operate) will save power if the sampling operation is a burst operation. In IDLE Mode, the digital current consumption is only 0.6mA/MHz, with no ADC, thus the current consumption at 18.432 MHz =11.1 miscalculating the average supply current for one sample period (similarly to Example 2, assuming a 10 kHz sampling rate and low-power tracking mode), the average current is estimated to be 11.9mA附录4 英文资料翻译电源管理技术及计算本设计应用于下列器件C8051F000、C8051F001、C8051F002、C8051F005、C8051F006、C8051F010、C8051F011、C8051F012、C8051F015、C8051F016、C8051F0171 引言本应用笔记讨论电源管理技术及计算C8051F00x和C8051F01x Sock中的功率消耗的方法。

电子电气类专业毕业设计外文翻译

附录一：外文原文Super capacitors - An OverviewKey words: Electrostatic capacitor; Electrolytic capacitor; Ceramic capacitor;Electrical double layer capacitor; Super Capacitor1.INTRODUCTIONThis paper offers a concise review on the renaissance of a conventional capacitor toelectrochemical double layer capacitor or super capacitor. Capacitors are fundamental electrical circuitelements that store electrical energy in the order of microfarads and assist in filtering. Capacitors havetwo main applications; one of which is a function to charge or discharge electricity. This function isapplied to smoothing circuits of power supplies, backup circuits of microcomputers, and timer circuitsthat make use of the periods to charge or discharge electricity. The other is a function to block the flowof DC. This function is applied to filters that extract or eliminate particular frequencies. This isindispensable to circuits where excellent frequency characteristics are required. Electrolytic capacitorsare next generation capacitors which are commercialized in full scale. They are similar to batteries in cell construction but the anode and cathode materials remain the same. They are aluminum, tantalum and ceramic capacitors where they use solid/liquid electrolytes with a separator between two symmetrical electro des.An electrochemical capacitor (EC), often called a Super capacitor or Ultra capacitor, stores electrical charge in the electric double layer at a surface-electrolyte interface, primarily in high-surface-area carbon. Because of the high surface area and the thinness of the double layer, these devices can have very a high specific and volumetric capacitance. This enables them to combine a previously unattainable capacitance density with an essentially unlimited charge/discharge cycle life. The operational voltage per cell ,limited only by the breakdown potential of the electrolyte, is usually<1 or <3 volts per cell for aqueous or organic electrolytes respectively.The concept of storing electrical energy in the electric double layer that isformed at the interface between an electrolyte and a solid has been known since the late 1800s. The first electrical device using double-layer charge storage was reported in 1957 by H.I. Becker of General Electric (U.S. Patent 2,800,616).Unfortunately, Becker’s device was imp ractical in that, similarly to a flooded battery, both electrodes needed to be immersed in a container of electrolyte, and the device was never comercialised.Becker did, however, appreciate the large capacitance values subsequently achieved by Robert A. Rightmire, a chemist at the Standard Oil Company of Ohio (SOHIO), to whom can be attributed the invention of the device in the format now commonly used. His patent (U.S. 3,288,641), filed in 1962 and awarded in late November 1966, and a follow-on patent (U.S. Patent 3,536,963) by fellow SOHIO researcher Donald L. Boos in 1970, form the basis for the many hundreds of subsequent patents and journal articles covering all aspects of EC technology.This technology has grown into an industrywith sales worth severalhundred million dollars per year. It is an in dustry that is poised today for rapid growth in the near term with the expansion of power quality needs and emerging transportation applications.Following the commercial introduction of NEC’s Super Capacitor in 1978, under licence from SOHIO, EC have evolved through several generations of designs. Initially they were used as back-up power devices for v is for cells ranging in size from small millifarad size devices with exceptional pulse power performance up to devices rated at hundreds of thousands of farads, with systems in some applications operating at up to 1,500 volts. The technology is seeing increasingly broad use, replacing batteriesolatile clock chips and complementary metal-oxide-semiconductor (CMOS) computer memories. But many other applications have emerged over the past 30 years, including portable wireless communication, enhanced power quality for distributed power generation systems, industrial actuator power sources, and high-efficiency energy storage for electric vehicles(EVs) and hybrid electric vehicles (HEVs).Overall, the unique attributes of ECs often complement the weaknesses of other power sources like batteries and fuel cells.Early ECs were generally rated at a few volts and had capacitance values measured from fractions of farads up to several farads. The trend today in some cases and in others complementing their performance.The third generation evolution is the electric double layer capacitor, where the electrical charge stored at a metal/electrolyte interface is exploited to construct astorage device. The interface can store electrical charge in the order of 610Farad. The main component in the electrode construction is activated carbon. Though this concept was initialized and industrialized some 40 years ago, there was a stagnancy in research until recent times; the need for this revival of interest arises due to the increasing demands for electrical energy storage in certain current applications like digital electronic devices, implantable medical devices and stop/start operation in vehicle traction which need very short high power pulses that could be fulfilled by electric double layer capacitors. They are complementary to batteries as they deliver high power density and low energy density. They also have longer cycle life than batteries and possess higher energy density as compared to conventional capacitors. This has led to new concepts of the so-called hybrid charge storage devices in which electrochemical capacitor is interfaced with a fuel cell or a battery. These capacitors using carbon as the main electrode material for both anode and cathode with organic and aqueous electrolytes are commercialized and used in day to-day applications. Fig.1 presents the three types of capacitors depicting the basic differences in their design and construction.Figure 1.Schematic presentation of electrostatic capacitor, electrolytic capacitor and electrical double layer capacitor.EDLCs, however suffer from low energy density. To rectify these problems, recently researchers try to incorporate transition metal oxides along with carbon in the electrode materials. When the electrode materials consist of transition metal oxides, then the electrosorption or redox processes enhance the value of specific capacitance ca. 10 -100 times depending on the nature of oxides. In such a situation, the EDLC is called as super capacitor or pseudo capacitor . This is the fourth generation capacitor. Performance of a super capacitor combines simultaneously two kinds of energy storage, i.e. non-faradic charge as in EDLC capacitors and faradaic charge similar toprocesses proceeding in batteries. The market for EC devices used for memory protection in electronic circuitry is about $150-200 million annually. New potential applications for ECs include the portable electronic device market, the power quality market, due particularly to distributed generation and low-emission hybrid cars, buses and trucks. There are some published reviews on capacitors and super capacitors . In the present overview, the evolution of electrochemical double layer capacitors starting from simple electrostatic capacitors is summarized.2. EXPERIMENTAL PARTThe invention of Leiden jar in 1745 started the capacitor technology; since then, there has been tremendous progress in this field. In the beginning, capacitors are used primarily in electrical and electronic products, but today they are used in fields ranging from industrial application to automobiles, aircraft and space, medicine, computers, games and power supply circuits. Capacitors are made from two metallic electrodes (mainly Si) placed in mutual opposition with an insulating material (dielectric) between the electrodes for accumulating an electrical charge. The basic equation relating to the capacitors is:C = εS/d (1)where C(μF) is the electrostatic capacity, the dielectric constant of the dielectric, S (cm2) the surface area of the electrode and d (cm) the thickness of the dielectric. The charge accumulating principle can be described as follows: when a battery is connected to the capacitor, flow of current induces the flow of electrons so that electrons are attracted to the positive terminal of the battery and so they flow towards the power source. As a result, an electron deficiency develops at the positive side, which becomes positively charged and an electron surplus develops at the negative side, which becomes negatively charged. This electron flow continues until the potential difference between the two electrodes becomes equal to the battery voltage. Thus the capacitor gets charged. Once the battery is removed, the electrons flow from the negative side to the side with an electron deficiency; this process leads to discharging. The conventional capacitors yield capacitance in the range of 0.1 to 1 μF with a voltage range of 50 to 400 V. Various materials such as paper (ε, 1.2-2.6), paraffin (ε 1.9-2.4), polyethylene (2.2-2.4), polystyrene (ε, 2.5-2.7), ebonite (ε, 2-3.5), polyethylene tetraphtharate (ε,3.1-3.2), water (ε, 80) sulfur（ε, 2-4.2), steatite porcelain (ε, 6-7), Al porcelain (ε, 8-10), mica（ε, 5-7)and insulated mineral oil (ε, 2.2-2.4) are used as dielectrics in capacitors.The capacitance output of these silicon based capacitors is limited and has to cope with low surface-to volume ratios of these electrodes. To increase the capacitance, as per eq., one has to increase to ∂or S and decrease; however the ∂value is largely determined by the working voltage and cannot be tampered. When aiming at high capacitance densities, it is necessary to combine the mutual benefits achieved with a high permittivity insulator material and an increased effective surface area. With Si as the substrate material, electrochemical etching produces effective surface area. The surface area of this material gets enlarged by two orders of magnitude compared to unetched surface. Electrochemically formed macroporous Si has been used for the preparation of high aspect ratio capacitors with layered SiO2/Si3N4/SiO2 insulators. Research work on the modification of conventional capacitors to increase the specific capacitance is also in progress. Approximately 30 times higher capacitance densities are reported recently for Si/Al2O3/ZnO: Al capacitor where Si is electrochemically etched porous one. Another way identified to increase the surface area of the electrodes is to form anodically formed oxides (Al, Ta); however, ceramic capacitors are based on the high dielectric constant rather than the electrode area.3. ELECTROLYTIC CAPACITORSThe next generation capacitors are the electrolytic capacitors; they are of Ta, Al and ceramic electrolytic capacitors. Electrolytic capacitors use an electrolyte as conductor between the dielectrics and an electrode. A typical aluminum electrolytic capacitor includes an anode foil and a cathode foil processed by surface enlargement and or formation treatments. Usually, the dielectric film is fabricated by anodizing high purity Al foil for high voltage applications in boric acid solutions. The thickness of the dielectric film is related to the working voltage of the aluminum electrolytic capacitor. After cutting to a specific size according to the design specification, a laminate made up of an anode foil, a cathode foil which is opposed to the dielectric film of the anode foil and a separator interposed between the anode and cathode foils, is wound to provide an element. The wound element does not have any electricalcharacteristics of electrolytic capacitor yet until completely dipped in an electrolyte for driving and housed in a metallic sheathed package in cylindrical form with a closed-end equipping a releaser. Furthermore, a sealing material made of elastic rubber is inserted into an open-end section of the sheathed package and the open-end section of the sheathed package by drawing, whereby an aluminum electrolytic capacitor is constituted. Electrolytic aluminum capacitors are mainly used as power supplies for automobiles, aircraft, space vehicles, computers, monitors, motherboards of personal computers and other electronics.There are two types of tantalum capacitors commercially available in the market; wet electrolytic capacitors which use sulfuric acid as the electrolyte and solid electrolytic capacitors which use MnO2 as the solid electrolyte. Though the capacitances derived from both Ta and Al capacitors are the same, Ta capacitors are superior to Al capacitors in temperature and frequency characteristics. For analog signal systems, Al capacitors produce a current-spike noise which does not happen in Ta capacitors. In other words, Ta capacitors are preferred for circuits which need high stability characteristics. The total world wide production of Al electrolytic capacitors amounts to US$ 3.8 billion, 99% of which are of the wet type. Unlike Ta solid electrolytic capacitors, the solid electrolyte materials used are of organic origin; polypyrrole, a functional polymer and TCNQ (7,7, 8, 8- tetracyanoquniodimethane) an organic semiconductor. Next, MnO2 solid electrolyte material is formed on the surface of that dielectric layer and on top of that a layer of polypyrrole organic solid electrolyte material is formed by electrolytic synthesis. Following this, the positive and negative electrodes are mounted to complete the electronic component. However, the capacitances of these electrolytic capacitors are in the range 0.1 to 10F with a voltage profile of 25 to 50 V.The history of development of electrolytic capacitors which were mass produced in the past as well as today is presented by S. Niwa and Y. Taketani . Many researchers try to improve the performance of these electrolytic capacitors by modifying the electrode or electrolyte. Generally, the increases in effective surface area (S) are achieved by electrolytic etching of aluminum substrate before anodization, but now it faces with the limit. It is also very difficult to decrease d because the d value is largely decided when the working voltages are decided. Increase in may be a possible routine to form composite dielectric layers by incorporating relatively large value compounds. Replacement of MnO2 by polypyrrole solid electrolyte was reported to reduce electrostatic resistance due to its higher conductivity; aromaticsulfonate ions were used as charge compensating dopant ions .A tantalum capacitor with Ta metal as anode, polypyrrole as cathode and Ta2O5 dielectric layer was also reported. In the Al solid electrolytic capacitors, polyaniline doped with inorganic and organic acids was also studied as counter electrode. In yet another work, Al solid electrolytic capacitor with etched Al foil as anode, polyaniline / polypyrrrole as cathode and Al2O3 as dielectric was developed. Ethylene carbonate based organic electrolytes and -butyrolactone based electrolytes have been tried as operating electrolytes in Al electrolytic capacitors. Masuda et al. have obtained high capacitance by electrochemically anodizing rapidly quenching Al-Ti alloy foil. Many researchers have tried the other combination of alloys such as Al-Zr, Al-Si, Al-Ti, Al-Nb and Al-Ta composite oxide films. Composite oxide films of Al2O3-(Ba0.5Sr0.5TiO3) and Al2O3- Bi4Ti3O12 on low-voltage etched aluminum foil were also studied. Nb-Ta-Al for Ta electrolytic capacitors was also tried as anode material .A ceramic capacitor is a capacitor constructed of alternating layers of metal and ceramic, with the ceramic material acting as the dielectric. Multilayer ceramic capacitors (MLCs) typically consist of ~100 alternate layers of electrode and dielectric ceramics sandwiched between two ceramic cover layers. They are fabricated by screen-printing of electrode layers on dielectric layers and co-sintering of the laminate. Conventionally, Ag-Pd is used as the electrode material and BaTiO3 is used as the dielectric ceramic. From 2000 onwards, the MLCs market has been growing in pace with the exponential development of communications. They are produced in the capacitance range of 10 F (normally the range of Ta and Al electrolytic capacitors); they are highly useful in high frequency applications. Historically, a ceramic capacitor is a two-terminal non-polar device. The classical ceramic capacitor is the disc capacitor. This device predates the transistor and was used extensively in vacuum-tube equipment (e.g radio receivers) from c. a. 1930 through the 1950s and in discrete transistor equipment from the 1950s through the 1980s. As of 2007, ceramic disc capacitors are in widespread use in electronic equipment, providing high capacity and small size at low price compared to the other types.The other ceramic materials that have been identified and used are CaZrO3, MgTiO3, SrTiO3 etc. A typical 10 F MLC is a chip of size (3.2 x 1.6 x 1.5 mm). Mn, Ca, Pd , Ag etc are some of the other internal electrodes used. Linear dielectrics and antiferroelectrics based o strontium titante have been developed for high voltage disk capacitors. These are applicable for MLCs with thinner layers because of their high coercive fields. One of the most critical material processing parameters is the degreeof homogeneous mixing of additive in the slurry. The binder distribution in the green ceramic sheet, the degree of surface roughness, fine size nickel powder, formation of green sheet, electrode deposition ad sheet stacking etc play a crucial role in the process technology. Any one of these facts if mishandled would result in the failure of the device. For instance, providing a roughess of 5 m thick green sheet to 0.5 m is mandatory so that a smooth contact surface with the inner nickel electrode can be established. This is a very important factor in avoiding the concentration of electric filed at asperities, where the charge emission from the electrode is accelerated, resulting in short failure. Conventional sheet/printing method has a technical limit of producing a thickness around 1 m dielectric; in order to decrease the thickness further, thin film technologies like CVD, sputtering, plasma-spray etc has to be used.The other types of capacitors are film capacitors which use thin polyester film and polypropylene film as dielectrics and meta-glazed capacitors which incorporate electrode plates made of film vacuum evaporated with metal such as Al. Films can be of polyester, polypropylene or polycarbonate make. Also capacitors are specified depending on the dielectric used such as polyester film capacitor, polypropylene capacitor, mica capacitor, metallized polyester film capacitor etc.4. DOUBLE LAYER CAPACITORSElectric/electrochemical double layer capacitor (EDLC) is a unique electrical storage device, which can store much more energy than conventional capacitors and offer much higher power densitythan batteries. EDLCs fill up the gap between the batteries and the conventional capacitor, allowing applications for various power and energy requirements i.e., back up power sources for electronic devices, load-leveling, engine start or acceleration for hybrid vehicles and electricity storage generated from solar or wind energy. EDLC works on the principle of double-layer capacitance at the electrode/electrolyte interface where electric charges are accumulated on the electrode surfaces and ions of opposite charge are arranged on the electrolyte side.Figure 2.Charge storage mechanism of an EDLC cell under idle and charged conditions.Fig. 2 shows the mechanism of charge storage in an EDLC cell and Fig. 3 shows the configuration of an typical EDLC cell. There are two main types of double layer capacitors as classified by the charge storage mechanism: (i) electrical double-layer capacitor; (ii) electrochemical double layer capacitor or super/pseudocapacitor. An EDLC stores energy in the double-layer at the electrode/electrolyte interface, whereas the supercapacitor sustains a Faradic reaction between the electrode and the electrolyte in a suitable potential window. Thus the electrode material used for the construction of the cell for the former is mainly carbon material while for the latter, the electrode material consist of either transition metal oxides or mixtures of carbon and metal oxides/polymers. The electrolytes can be either aqueous or non-aqueous depending on the mode of construction of EDLC cell.Figure 3.Typical configuration of an EDLC cellThere are two general directions of interest. One is the long term goal of the development of electrical propulsion for vehicles, and the other is the rapid growth of portable electronic devices that require power sources with maximum energy content and the lowest possible size and weight.5. CONCLUSIONSAccording to a market survey by Montana, super capacitors are becoming a promising solution for brake energy storage in rail vehicles. The expected technological development outside railway sector is also shown to be highly dynamic: diesel electric vehicles, catenary free operation of city light rail, starting system for diesel engines, hybrid-electric cars, industrial applications, elevators, pallet trucks etc. The time horizon expected for development is next 5 to 10 years. The main development goals will be,· long life time· increase of the rated voltage· improvements of the range of operating temperature· increase of the energy and power densitiesVery recently, hybrid car is introduced in the market but it is turned to be very expensive and out of common man’s reach. Shortage and cost of fossil fuels already instigated alternate technologies viable for traction purposes. In such a situation,EDLCs are also useful to store energy generated from non-conventional energy sources. A future possibility of service centers set up for EDLC supply similar to petrol (as on date) is not far as the main setbacks in technology development may take a decade for fruitful results.附录二：外文译文超级电容器-概述关键词：静电电容，电解电容器，陶瓷电容器，双电层 ,电容器，超级电容器1．引言本文为电化学双层电容器或超级电容器提供在一台常规电容器，简明的介绍新生的电化学双电层电容器或超级电容器。

电子电气专业毕业外文翻译

DC Switching Power Supply Protection TechnologyAbstract: The DC switching power supply protection system, protection system design principles and machine protection measures, an analysis of switching power supply in the range of protected characteristics and its design methodology, introduced a number of practical protection circuit.Keywords: switching power supply protection circuit system designA、IntroductionDC switching regulator used in the price of more expensive high-power switching devices, the control circuit is also more complex, In addition, the load switching regulators are generally used a large number of highly integrated electronic systems installed devices. Transistors and integrated device tolerance electricity, less heat shocks. Switching Regulators therefore should take into account the protection of voltage regulators and load their own safety. Many different types of circuit protection, polarity protection, introduced here, the program protection, over-current protection, over-voltage protection, under-voltage protection and over-temperature protection circuit. Usually chosen to be some combination of protection, constitutes a complete protection system.B、Polarity protectionDC switching regulator input is generally not regulated DC power supply. Operating errors or accidents as a result of the situation will take its wrong polarity; switching power supply will be damaged. Polarity protection purposes, is to make the switching regulator only when the correct polarity is not connected to DC power supply regulator to work at. Connecting a single device can achieve power polarity protection. Since the diode D to flow through switching regulator input total current, this circuit applied in a low-power switching regulator more suitable. Power in the larger occasion,while the polarity protection circuit as a procedure to protect a link, save the power required for polarity protection diodes, power consumption will be reduced. In order to easy to operate, make it easier to identify the correct polarity or not, collect the next light.C、Procedures to protectSwitching power supply circuit is rather complicated, basically can be divided into low-power and high-power part of the control part of the switch. Switch is a high-power transistors, for the protection of the transistor switch is turned on or off power safety, we must first modulator, amplifier and other low-power control circuit. To this end, the boot to ensure the correct procedures. Switching Regulators generally take the input of a small inductor, the input filter capacitor. Moment in the boot, filter capacitor will flow a lot of surge current, the surge current can be several times more than the normal input current. Such a large surge current may contact the general power switch or relay contact melting, and the input fuse. In addition, the capacitor surge current will damage to shorten the life span of premature damage. To this end, the boot should be access to a current limiting resistor, through the current limiting resistor to capacitor charging. In order not to make the current limiting resistor excessive power consumption, thus affecting the normal switching regulator, and the transient process in the boot after a short period then automatically relays it to DC power supply directly to the switching regulator power supply. This circuit switching regulator called a "soft start" circuit.Switching regulator control circuit of the logic components required or op-amp auxiliary power supply. To this end, the auxiliary power supply must be in the switch circuit. This control circuit can be used to ensure the boot. Normal boot process is: to identify the polarity of input power, voltage protection procedures → boot → auxiliary power supply circuit and through current limiting resis tor R of the switching regulator input capacitor C →charge modulation switching regulator circuit, → short-circuit current limiting resistor stability switching regulator.In the switching regulator, the machines just because the output capacitance, and charge to the rated output voltage value of the need for a certain period of time. During this time, sampling the output amplifier with low input voltage sampling, closed-loop regulation characteristics of the system will force the switching of the transistor conduction time lengthened, so that switching transistor during this period will tend to continuous conduction, and easily damaged. To this end, the requirements of this paragraph in the boot time, the switch to switch the output modulation circuit transistor base drive signal of the pulse width modulation, can guarantee the switching transistor by the cut-off switches are becoming more and more normal state, therefore the protection of the setting up of a boot to tie in with the soft start.D、Over-current protectionWhen the load short-circuit, overload control circuit failure or unforeseen circumstances, such as would cause the flow of switching voltage regulator transistor current is too large, so that increased power tubes, fever, if there is no over-current protection device, high power switching transistor may be damaged. Therefore, the switching regulator in the over-current protection is commonly used. The most economical way is to use simple fuse. As a result of the heat capacity of small transistors, general fuse protection in general can not play a role in the rapid fuse common fuse. This method has the advantage of the protection of vulnerable, but it needs to switch transistor in accordance with specific security requirements of the work area to select the fuse specifications. This disadvantage is over-current protection measures brought about by the inconvenience of frequent replacement of fuses.Linear voltage regulator commonly used in the protection and currentlimiting to protect the cut-off in the switching regulator can be applied. However, according to the characteristics of switching regulators, the protection circuit can not directly control the output transistor switches, and over current protection must be converted to pulse output commands to control the modulator to protect the transistor switch. In order to achieve over-current protection are generally required sampling resistor in series in the circuit, this will affect the efficiency of power supply, so more for low-power switching regulator of occasions. In the high-power switching power supply, by taking into account the power consumption should be avoided as far as possible access to the sampling resistor. Therefore, there will usually be converted to over-current protection, and under-voltage protection.E、Over-voltage protectionSwitching regulator's input over-voltage protection, including over-voltage protection and output over-voltage protection. Switching regulator is not used in DC power supply voltage regulator and rectifier, such as battery voltage, if too high, so switching regulator is not working properly, or even damage to internal devices, therefore, it is necessary to use the input over-voltage protection circuit. Using transistors and relays protection circuit.In the circuit, when the input DC power supply voltage higher than the voltage regulator diode breakdown voltage value, the breakdown voltage regulator tube, a current flowing through resistor R, so that V turn-on transistor, relay, normally closed contact off open, cut off the input. Voltage regulator voltage regulator which controls the value of Vs. = Earwax-UBE. The polarity of input power with the input protection circuit can be combined with over-voltage protection, polarity protection constitute a differential circuit and over voltage protection.Output over-voltage protection switching power supply is essential. In particular, for the 5V output of the switching regulator, it is a lot of load on a high level of integration of the logic device. If at work, switching regulator sudden damage to the switch transistor, the output potential may be increased immediately to the importation of non-regulated DC power supply voltage value, causing great loss instantaneous. Commonly used method is short-circuit protection thirsted. The simplest over-voltage protection circuit. When the output voltage is too high, the regulator tube breakdown triggered thirstier turn-on, the output short-circuit, resulting in over-current through the fuse or circuit protective device to cut off the input to protect the load. This circuit is equivalent to the response time of the opening time of thirstier is about 5 ~ 10μs. The disadvantage is that its action is fixed voltage, temperature coefficient, and action points of instability. In addition, there is a voltage regulator control parameters of the discrete, model over-voltage start-up the same but has different values, difficult to debug. Esc a sudden increase in output voltage, transistors V1, V2 conduction, the thruster conduction. Reference voltage Vs. by type.F、Under-voltage protectionOutput voltage below the value to reflect the input DC power supply, switching regulator output load internal or unusual occurrence. Input DC power supply voltage drops below the specified value would result in switching regulator output voltage drops, the input current increases, not only endanger the switching transistor, but also endanger the input power. Therefore, in order to set up due to voltage protection. Due to simple voltage protection.When no voltage regulator input normal, ZD breakdown voltage regulator tube, transistors V conduction, the relay action, contact pull-in, power-switching regulator. When the input below the minimum allowable voltage value, the regulator tube ZD barrier, V cut-off, contact Kai-hop,switching regulator can not work. Internal switching regulator, as the control switch transistor circuit disorders or failure will decrease the output voltage; load short-circuit output voltage will also decline.Especially in the reversed-phase step-up or step-up switching regulator DC voltage of the protection due to over-current protection with closely related and therefore more important. Implementation of Switching Regulators in the termination of the output voltage comparators.Normally, there is no comparator output, once the voltage drops below the allowable value in the comparator on the flip, drive alarm circuit; also fed back to the switching regulator control circuit, so that switching transistor cut-off or cut off the input power.G、Over-temperature protectionSwitching regulator and the high level of integration of light-weight small volume, with its unit volume greatly increased the power density, power supply components to its work within the requirements of the ambient temperature is also a corresponding increase. Otherwise, the circuit performance will deteriorate premature component failure. Therefore, in high-power switching regulator should be set up over-temperature protection.Relays used to detect the temperature inside the power supply temperature, when the internally generated power supply overheating, the temperature of the relay on the action, so that whole circuit in a warning alarm, and the realization of the power supply over-temperature protection. Temperature relay can be placed in the vicinity of the switching transistor, the general high-power tube shell to allow the maximum temperature is 75 ℃, adjust the temperature setting to 60 ℃. When the shell after the temperature exceeds the allowable value to cut off electrical relay on the switch protection. Semiconductor switching device thermal "hot thirstier," in the over-temperature protection, played an important role. It can be used asdirected circuit temperature. Under the control of p-hot-gate thirstier (TT102) characteristics, by RT value to determine the temperature of the device turn-on, RT greater the temperature the lower the turn-on. When placed near the power switching transistor or power device, it will be able to play the role of temperature instructions. When the power control the temperature of the shell or the internal device temperature exceeds the allowed value, the heat conduction thirstier on, so that LED warning light. If the opt coupler with, would enable the whole circuit alarm action to protect the switching regulator. It can also be used as a power transistor as the over-temperature protection, crystal switch the base current by n-type gate control thirstier TT201 thermal bypass, cut-off switch to cut off the collector current to prevent overheating.I、ConclusionDiscussed above in the switching regulator of a variety of conservation, and introduces a number of specific ways to achieve. Of a given switching power supply is concerned, but also protection from the whole to consider the following points:1) The switching regulator used in the switching transistor in the DC security restrictions on the work of regional work. The transistor switches selected by the manual available transistors get DC safe working area. According to the maximum collector current to determine the input value of over-current protection. However, the instantaneous maximum value should be converted to the average current. At rated output current and output voltage conditions, the switch of the dynamic load line does not exceed a safe working area DC maximum input voltage, input over-voltage protection is the voltage value.2)The switching regulator output limit given by the technical indicators within. Work within the required temperature range, the switching regulator's output voltage, the lower limit of the output is off, due to thevoltage value of voltage protection. Over-current protection can be based on the maximum output current to determine. False alarm in order not to protect the value of a certain margin to remain appropriate.3)From the above two methods to determine the protection after the power supply device in accordance with the needs of measures to determine the alarm. Measures the general alarm sound and light alarm two police. Voice of the police applied to more complex machines, power supply parts and do not stand out in a place, it can give staff an effective warning of failure; optical Police instructions can be eye-catching and fault alarm and pointed out that the fault location and type. Protection measures should be protected as to determine the location. In the high-power, multi-channel power supply, always paying, DC circuit breakers, relays, etc. high-sensitivity auto-protection measures, to cut off the input power supply to stop working the system from damage. Through the logic control circuit to make the appropriate program cut-off switch transistor is sensitive it is convenient and economic. This eliminated large, long response time, the price of your high-power relay or circuit breaker.4) The power of putting in the protection circuit will be affected after the reliability of the system, for which want to protect the reliability of the circuit itself is higher in order to improve the reliability of the entire power system, thereby increasing its own power supply MTBF. This requires the protection of strict logic, the circuit is simple, at least components, In addition to the protection circuit should also be considered a failure of maintenance of their difficulty and their power to protect the damage.Therefore, we must be comprehensive and systematic consideration of a variety of switching power supply protection measures to ensure the normal operation of switching power supplies and high-efficiency and high reliability.直流开关稳压电源的保护技术摘要：讨论了直流开关稳压电源的保护系统,提出保护系统设计的原则和整机保护的措施，分析了开关稳压电源中的各种保护的特点及其设计方法,介绍了几种实用保护电路。

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附录1：外文资料翻译A1.1外文资料题目26.22 接地故障电路开关我们目前为止报道的接地方法通常是充分的, 但更加进一步的安全措施在某些情况下是必要的。

假设例如, 有人将他的手指伸进灯口（如Fig.26.45示）。

虽然金属封入物安全地接地, 但那人仍将受到痛苦的震动。

或假设1个120V 的电炉掉入游泳池。

发热设备和联络装置将导致电流流入在水池中的危害，即使电路的外壳被安全地接地，现在已经发展为当这样的事件发生时，设备的电源将被切断。

如果接地电流超过5mA ，接地开关将在5 ms 内跳掉，这些装置怎么运行的？如Fig.26.46所示，一台小变流器缠绕上导线，第二步是要连接到可能触发开合120 V 线的一台敏感电子探测器。

在正常情况下流过导体的电流W I 与中性点上的电流N I 准切的相等，因此流经核心的净潮流(N W I I -)是零。

结果，在核心没有产生电流，导致的电压F E 为零，并且开关CB 没有动作。

假设如果某人接触了一个终端(图Fig.26.45示)，故障电流F I 将直接地从载电线漏到地面，这是可能发生的。

如果绝缘材料在马达和它的地面封入物之间断开，故障电流也会被产生。

在以下任何情况下，流经CT 的孔的净潮流等于F I 或L I ，不再是零。

电流被产生，并且产生了可以控制CB 开关的电压F E 。

由于5 mA 不平衡状态只必须被检测出，变压器的核心一定是非常有渗透性的在低通量密度。

Supermalloy 是最为常用的，因为它有相对渗透性典型地70000在通量密度仅4mT 。

26.23 t I 2是导体迅速发热的因素它有时发生于导体短期内电流远大于正常值的情况下，R I 2损失非常大并且导体的温度可以在数秒内上升几百度。

例如，当发生严重短路时，在保险丝或开关作用之前，会有很大的电流流过导体和电缆。

此外，热量没有时间被消散到周围，因此导体的温度非常迅速地增加。

在这些情况下什么是温度上升？假设导体有大量m ，电阻R 和热量热容量c 。

而且，假设电流是I ，并且那它流动在t 少于15秒期间。

在导体上引起的热Rt I Q 2=从Eq.3.17，在功率一定的情况下我们可以计算导体上升的温度差：t mc Q ∆=因此由t mc Rt I ∆=2得出 )(2t I mcR t =∆ 因而断定一个导体的温度上升取决于t I 2因素。

众所周知：高温会破坏包裹在导体表面的绝缘。

因此确定温度上升因素t I 2是非常重要的，因为它在短路情况下，决定导体的温度上升。

例如，一个最初在温度C ︒90的No.2AWG 铜导体，如果它的温度在短路时必须控制在C ︒250，不可能承受t I 2因素超出s A 261022⨯。

一般来说，t I 2因素可以被用于计算知道(a)导体的横断面， (b)它的构成(铜或铝)和(c)它能承受的最高温度。

铜和铝的t I 2因素给出以下等式：对于铜导体， )234234(log 105.11010242θθ++⨯=m A t I 对于铝导体， )234234(log 102.5010242θθ++⨯=m A t I 其中：I=短路电流（A ）t=短路的时间（s ）A =导体没有计算空的空间的网横断面（mm 2） =0θ导体的最初温度(c ︒)=m θ导体的最后温度(c ︒)例子26-1___________________________________________一条由铝导体NO3.AWG 制成且横断面为26.6mm 的架空线。

在正常情况下这个导体可能连续运载电流160 A 。

a.在短路期间，计算最大可允许的t I 2因素，知道最初的温度是c ︒80，并且最大温度不应该超出c ︒250。

b.在此架空线上有2000A 的最大短路电流，问它在无需超出c ︒250温度极限的情况下运行多久？解答a.由Eq.26.5我们发现 )234234(log 102.5010242θθ++⨯=m A t I =80234250234(log 102.51024++⨯A =7s A 2610⨯b.2000A 电流可运行的时间tt I 2=7610⨯ 2000t 2 =7610⨯t = 1.75s例子26-2___________________________________________它提议使用NO.30AWG 铜丝作为一根临时保险丝。

如果它最初的温度是50c ︒，计算以下： a.需要熔化导线的t I 2 (铜熔化在1083c ︒)b.如果短路电流是30A ，需要熔化导线的时间解答a.由我们有的Eq.26.4 )502341083234(log 0507.0105.1110242++⨯⨯=t I =197 A s 2b.从电流为30A 可得到t I 2=197301972=tt=0.22s因此，保险丝可能在220ms 后被熔断。

26.24 保险丝的角色为了保护导体在短路期间免受过热温度的毁坏，一系列保险丝必须安置在导体上。

保险丝是经过选择的，目的是它的规定值t I 2比将保护导体上升的过热温度要少。

实际上，我们要保险丝在导体获得一个危险温度之前熔断，通常采取是250c ︒。

实践上，保险丝的规定值t I 2远在产生导体温度的t I 2最大限度之下。

尽管如此，导体的规定值t I 2在保险丝的选择时是一个重要的因素。

26.25 在建筑内的电子设备安装电子分布式系统在建筑内是消费者和电能初始源之间最后的链接。

所有这一类建筑内部的分布式系统，不管他们大或小，必须符合一些基本要求：1. 安全性a. 电击的保护b. 对导体物理损伤的保护c. 对超载保护d. 对恶劣环境的保护2. 导体的电压降它不应该超出1或2%3. 估计寿命分布式系统应该持续最小限度于50年4. 经济性电力设施的费用应该是在考虑到当前一般标准的最小值。

标准由全国电子代码规定，并且电子设施在它可以被放入服务之前必须由审查员批准。

26.26 电力设施的主要成分许多成分组成了电子设施。

结构图Figs.26.47和26.48，与以下定义一起，将帮助读者了解某些更加重要的项目的意义。

1. 服务导体这些是在消费者之前从街道主馈线延长或从变压器对服务设备的导体。

2. 服务设备这些是必要的设备，通常包括开关或开关和保险丝以及他们的辅助部件，位于大厦或者其它结构服务导体的入口处，或是一个其他方面被定义的区域和意欲构成主控制和切断供应的方法。

3. 会议设备各种各样的记录在这个前提下预测电能消耗。

4 镶板一个盘区或小组盘区单位为汇编设计了以一个唯一盘区的形式; 包括公共汽车，自动过载电流设备和有或没有为光、热或者功率电路控制的开关；27.1 核电的安全尽管核电厂的安全与设计阶段的决策.施工前的谨慎的研究以及施工本身有着直接关系，但只有在电厂真正进入运行阶段，才有可能在各方面看到其核安全状况，如：由于其设计缺陷出现的事故危险质量不佳或运行故障。

保持安全水平为了保持安全水平，首先必须遵守设计所规定的运行限制。

这些限制在《安全分析报告》的“技术操作说明”中作了明确的陈述。

按照安全重要系统（IPS）进行一项详尽无疑的分析，同样也是为了确定哪一种设备需要进行定期的检测，哪一项无需检测（正常运行就是运行状况良好的充分证明）。

对每个系统和每次检测来说，《检测程序》文件对操作程序，操作标准和要求检测的周期等都作了明确的规定，这些规定成了运行人员制定检测计划表的基础。

提高安全水平，操作经验反馈由EDF采用的标准政策（EDF是一种主要PWR系统类型和有限的单个电厂序列数量）可保证通过特别重视预兆的分析极大的提高操作经验的价值。

这有双重目的：1．减少能够引起发电设备不能用的事故发生频率，即使这些事故可能对安全没有直接关系；2．减少可能对安全造成后果的严重事故的发生频率，实际上，以“多层保护”和故障存在为基础的核机组设计原理，认为严重的事故只能是那些单独事故和那些所谓不可能发生的事故同时发生的产物。

从核安全的角度考虑，操作反馈的主要目标如下：1确认可导致更为严重事故的预兆事故，以明确和贯彻在这类事故发生前所需采取的改正措施；2利用标准的机组（事故的一般方面，从修改研究等方面获取最大的效益）3如有必须修改之处，那么在将原理推广到整个电厂序列之前，要保证不会产生相反的副作用；4要利用在机组实际运行中所获得的数据，以统一安全标准，特别是对新厂更需要如此。

EDF是按如下方针制定其操作经验反馈系统的：1系统地收集尽可能多的数据资料，尽可能广泛地交流收集到的数据，特别是在EDF范围内；2在数据分析过程中，要尽可能地让设计人员，运行人员，制造厂商和安全机构一起参与；3吸取经验，这不仅有益于那些正在计划和建设中的机组，而且有益于那些目前正在运行的机组。

A1.2外文资料题目26.22 Ground-fault circuit breakerThe grounding methods we have covered so far are usually adequate,but further safety measures are needed in some cases.Suppose foe example , that a person sticks his finger into a lamp socket (Fig.26.45).Although the metal enclosure is securely grounded, the person will still receive a painful shock. Or suppose a 120 V eletric toster tumbles into a swimming pool. The heating elements and contacts will produce a hazardos leakage current throughout the pool ,ven if the frame of the toaster is securely grounded. Devices have been developed that will cut the source of power as soon as such accidents occur. These ground-fault circuit breaker will typically trip in 25 ms if the leakage current exceeds 5 mA. How do these protective devices operate ?A small current transformer surrounds the live and neutral wires as shown in Fig.26.46. The secondary is connected to a sensitive electronic detetor that can trigged a circuit breaker CB that is in series with the 120 V line.Under normal conditions the current I w in the line conductor is exactly equal to thecurrent I n in the neutral ,and so the net current (I W-I N) flowing through the hole in the toroidal core is zero. Consequently, no flux is produced in the core, the induced voltage E F is zero, and breaker CB does not trip.Suppose now that a fault current I F leaks directly from the live wire to ground . This could happen if someone touched a live terminal (Fig.26.45). A fault current I L would also be produced if the insulation broke down between a motor and its grounded enclosure . Under any of these conditions, the net current flowing through the hole of the CT is no longer zero but equal to I F or I L. A flux is set up and a voltage E F is induced, which trips CB. Because an imbalance of only 5 mA has to be detected, the core of the transformer must be verypermeable at low flux densities. Supermalloy TM is often used for this purpose because it has a relative permeability of typically 70000 at a flux density of only 4mT .26.23 rapid conductor heating: the I2t factorIt sometimes happens that a current far greater than normal flows for a brief period in a conductor . The I 2losses are than very large and the temperature of the conductor can rise several hundred degrees in a fraction Rof a second . For example, during a severe short-circuit, intense currents can flow in conductors and cables before the circuit is opened by the fuse or circuit breaker.Furthermore, the heat does not have time to be dissipated to the surroundings and so the temperature of the conductor increases very rapidly. What is the temperature rise under these condition?Suppose the conductor has a mass m, a resistance R, and a thermal heat capacity c. Moreover, suppose the current is I and that it flows for a period t that is typically less than 15 seconds. The heat generated in the conductor is given byRt I Q 2=Form Eq.3.17,we can calculate the temperature rise t ∆for a given value of Q :t mc Q ∆=hencet mc Rt I ∆=2from which)(2t I mcR t =∆ If follows that for a given conductor the temperature rise depends upon the I t 2 factor .It is well known that high temperature damage the insulation that covers a conductor. The I t 2 factor is ,therefore ,very important because it determines the temperature rise under short-circuit conditions. For example , a No.2AWG copper conductor, initially at a temperature of 90C ︒,cannot endure an It 2 factor in eccess of 222610A ⨯s if its temperature is to be limited to 250C ︒during a short-circuit.In general, the I t 2 factor can be calculated knowing (a) the cross section of the conductor, (b) itscomposition(copper or aluminum), and (c) the maximum temperature it can tolerate. The It 2 factor for copperand aluminum conductors are given by the following equations:for copper conductors, )234234(log 105.11010242θθ++⨯=m A t Ifor aluminum conductors,)234234(log 102.5010242θθ++⨯=m A t I whereI =short-circuit current []A=t duration of the short-circuit []sA = net cross-section of conductor without counting the empty spaces []2mm =0θ initial temperature of conductor []C ︒=m θfinal temperature of conductor []C ︒Example 26-1___________________________________________An overhead line made of aluminum conductor No.3 AWG has a cross-section of 26.6mm 2. Under normal conditions this conductor can continuously carry a current of 160 A. ,a Calculate the manximum permissible I t 2 factor during a short-circuit, knowing that the initial temperature is 80C ︒and that the manximum temperature should not exceed 250C ︒.,b A manximum short-circuit of 2000 A is foreseen on this overhead line. For how long can it circulate without exceeding the 250C ︒ temperature limit?Solution,a Using Eq.26.5 we find)234234(log 102.5010242θθ++⨯=m A t I =80234250234(log 102.51024++⨯A )=7s A 2610⨯,b The 2000 A current can flow for a time t given byI t 2=7610⨯2000t 2 =7610⨯t = 1.75sExample 26-1___________________________________________It is proposed to use a No.30 AWG copper wire as a temporary fuse. If its initial temperature is 50C ︒, calculate the following :,a The I t 2 needed to melt the wire ( copper melts at 1083C ︒),b The time needed to melt the wire if the short circuit current is 30 ASolutionForm Eq.26.4 we have)502341083234(log 0507.0105.1110242++⨯⨯=t I =197 A s 2,b For a current of 30 A we obtainI t 2=197301972=tt=0.22sThus, the fuse will blow in approximately 220ms.26.24 The role of fusesIn order to protect a conductor from excessive temperature during a short-circuit, a fuse must be placed in series with the conductor. The fuse must be selected so that its I t2rating is less than that which will protect an excessive temperature rise of the conductor. In effect, we want the fuse to blow before the conductor attains a dangerous temperature, usually taken to be 250C . In practice, the I t2rating of the fuse is such as to product conductor temperatures far below this maximum limit. Nevertheless, the I t2 rating of the conductor is an important element in the choice of the fuse.26.25 Electrical installation in buildingsThe electrical distribution system in a building is the final link between the consumer and the original source of electrical energy. All such in-house distribution systems, be they large or small, must meet certain basic requirements:1.Safetya.Protection against electric shockb.Protection of conductors against physical damagec.Protection against overloadsd.Protection against hostile environments2.Conductor voltage dropIt should not exceed 1 or 2 percent3.Life expectancyThe distribution system should last a minimum of 50 years4.EconomyThe cost of the installation should be minimized while observing the pertinent standards.Standards are set by the National Electrical Code and every electrical installation must be approved by an inspector before it can be put into service.26.26 Principal components of an electrical installationMany components are used in the markup of an electrical installation. The block diagrams of Figs.26.47 and 26.48, together with the following definitions, will help the reader understand the purpose of some of the more important items.1.Service Conductors. These are the conductors that extend form the street main or form atransformer to the service equipment on the consumer premises.2.Service Equipment. The necessary equipment, usually consisting of a circuit breaker or switch andfuses, and their accessories, located near the point of entrance of service conductors to a building orother structure, or an otherwise defined area, and intended to constitute the main control and means ofcutoff of the supply.3.Meeting Equipment. Various meters and recorders to indicate the electrical energy consumed on thepremises.4.Panel Board.A single panel or group of panel units designed for assembly in the form of a singlepanel; including buses, automatic over current devices, and with or without switches for the control oflight, heat, or power circuits;5.SafetyAlthough the safety of a nuclear power plant is directly linked to the decision taken at the design stage and to the care taken in pre-construction studies and construction itself, it is only really in operation that nuclear safety can be seen in all its various facets, i.e. the risk of accident due to weaknesses in the design, insufficient quality or operational error.Maintaining the Safety levelIn order to maintain the level of safety, it is first of all necessary to observe the operational limits of the design. These limitatio ns are set out in the “Technical Operating Specifications” volume of the Safety Analysis Report.An exhaustive analysis is also carried out on systems Important For Safety (IPS) to identify which equipment is required to undergo periodic testing and to justify which items do not require testing (normal operation is sufficient proof of good working order). For each system and test the “Test Procedure” document specifies the operating procedure, criteria and the required testing intervals. These instructions are used by the operators as the basis for preparing “Test Schedules”.27.1 Safety of Nuclear electricityThe standardization policy adopted by EDF (one major PWR system type and a limited number of individual plant series) justifies a major commitment to maximizing the value of operational experience by placing particular emphasis on the analysis of precursor incidents. This has a dual purpose:●To reduce the frequency of serious incidents liable to result in the generating equipment becomingunavailable, even if these is no direct bearing on safety.●To reduce the frequency of incidents likely to have consequences to safety , in practice, the design principlesfor nuclear units based on Defence In Depth and the presence of barriers are such that serious accidents could only result from a simultaneous combination of independent and improbable incidents.In terms of nuclear safety, the principal objectives of operational feedback are as follows:# to identify precursor incidents leading to more serious accidents in order to define and implement anycorrective measures required before any such accidents occur.# to take adventage of standardized units (the generic aspects of incidents, deriving maximum benefit from modification studies, ect )# to ensure, in cases where modification is necessary, that these are no adverse secondary effects before principle is extended to the entire plant series.# to utilize data gathered during actual operation of the installation in order to unify the level of safety, especially in the case of a new plant series.The guidelines on which EDF has based its operational experience feedback system are as follows:i.To systematically gather the maximum amount of data and circulate it as widely as possible, particularlywithin EDF.ii.To bring together as many as possible Designers. Operators, Manufacturers and Safety Authorities in the data analysis process.iii.To lean from experience on order to benefit not only those units planned or under construction but also units currently in service.。