基于PLC的恒压供水系统设计 英文资料

Constant Pressure Water Supply System Based plcAbstract: Based one simple analysis of the methods for water supply used domestically and abroad, this paper discusses the principl e and system’s structure of automatic water supply system by using frequency conversion speed regulation in detail. Then the system’s advantages are discussed and some key problems that should be pay attention to designing are presented.Keyword: Frequency conversion speed regulation; water supply with stable pressure: PID regulator.1、ForewordAt present, supply water in residential area and life of the skyscraper of our country generally adopt the way common frequently. It has heavy energy consumption, high noise, and there has a great deal of questions in the source of water, such as secondary pollution etc. And it is a kind of comparatively ideal mode to adjust the water supply device controlled rapidly with frequency conversion .Entering the middle and later periods of the 1990s, as the speed technology of frequency conversion achieves more development becomes perfect, the way of the full-automatic constant pressure that based on this technology supplied water has already been widely used in the developed country, and is becoming riper.In recent years, authors has made some real work on rapidly to the transformation in frequency conversion supply water design and construction of control system, have accumulated some experience, and has formed the view on some questions. The reason why the energy-conserving principle frequency conversion of the water pump system of speed adjustment becomes popularized , is mainly because that it has a better energy- conserving result. To pump system of frequency conversion, the water pump after adjusting the speed has functional relation of the following:Q1/Q2 =n1/n2 (1)H1/H2 = (n1/n2)2(2)of the type. Q1, Q2 represents the flow before and after the speed for the water pump respectively; N1, n2 represents the rotational speed before and after the speed for the water pump respectively; H1, H2 represents the lift before and after the speed for the water pump respectively.According the above: H1/H2 = (f1/f2)ly real lift of a water pump is power the square of frequency in direct radio. Therefore changing the power supply frequency of the electrical machinery of water pump through the frequency converter can control supporting water pressure strength of the water pump. 2 constant pressures as Fig. 1 shows supply water of the automatically controlled frequency conversion water -supply system principle block diagram. P1 is the give pressure value, p2 for the actual pressure value had examined from the pipeline of the pressure sensor, PID regulator passes the error operation of the two value, and through controlling the frequency output of the frequency converter, thus make the pressure of the pipeline remain throughout on establishing value p1.This system can measure users' instantaneous water pressure adjust automatically , regulate the amount of quantity of supplying water and operation conditions of the electrical machinery in view of the above. Can according to give water pressure strength to set for and control pressure value which needed , make the equipment in the constant pressure state all the time, can know from load characteristic of electrical machinery axle power and its the third power of in direct radio rotational speed of electrical machinery mixed, that is p1/p2=(n1/n2)3. For example, as the frequency converter output frequency for 35Hz (establish as 50Hz at most), that is to say that the actual rotational speed is 70% o'clock of specified rotational speed, the power consumption of the governor is 0.73 =0.343, account for specified 35%. That is tosay , the water pump is always in constant pressure and turn the working state of matching the way into the flow , is it is it keep to exceed to dispel and backset current have work loss. Constant speed transfer with frequency conversion speed axle power change curve as Fig. 2 shows , relatively can know, it is the most obvious that frequency conversion adjusts the energy-conserving result of speed way.2、Case analysesConstant pressure is it regulate flow of water to the purpose to up to constant pressure through suiting well rapidly in frequency conversion to supply water, the goal that it controls finally is the water pressure. Controlling the target has non-linear, lagging characteristics. The quality of PID regulator performance , has determined the quality of the water -supply system to a great extent When the system is during the course of starting and stopping, or the pressure establishing value changes by a large margin , because there is a very great deviation within short time, no matter the control algorithm of PID regulator adopts the increment type or the position type, its total mark one will fetch the cistern , water pump group and complement the fittingsto form relevantly. The core of this system is that frequency conversion adjusts the speed switch board, it monitors the pressure of the pipe network in real time through the pressure sensor, and change into the electric signal and offer the frequency converter to make operation, through the controlling commonly of frequency converter, programmable controller PLC and relay array, adjust the system of supplying water rapidly after forming perfect full-automatic frequency conversion. Frequency converter is various in kinds, for instance the types, such as Mitsubishi, Fuji, three Kenya and ABB, etc. Generally often select the pumps, special-purpose series of air blower for use. Whether take Mitsubishi FR-A140E as an example, it except general function had of brand , there are the following characteristics : The inside adopts the intellectual power module of IPM, it is lowest to make the noise of the electrical machinery to reduce; Frequency converter, and work-frequency power can is it switch over to go on frequently, user is it is it start , stop through PLC and switch over the order automatically to input to need only, can conveniently through to lock movement switch over different water pump each other contactor, and does not need to design the tedious control procedure by oneself like the thing that in the past , this is one of this peculiar functions of frequency converter; Built-in instantaneous power cut starts and retries and starts the function , in a situation that nobody guarded,even if can be started by oneself after the frequency converter shuts down, totally realize with the operation of the automatic way. PID regulator available frequency converter of system this built-in value very heavy, this will store deviation in regulates. During the process of dispelling the deviation to regulate, must lead to the fact the system and present greater ultra mediation long-time vibration, can produce the serious integration saturation phenomenon also at the same time, thus influence the normal running of the equipment. Is it drop the influence to most low to want , should adopt PID control method that integration separate among controlling algorithm, in order to reach the anticipated result. After dealing with like this, can shorten the system and reach steady transition course time greatly System allocate two 11kW water pump support 600 over resident water. Two pump offer large peak flow most when working at the same time, single platform meet the small flow and supply water at night. In addition all water pumps can run by way of frequency conversion, can circulate way soft to start, in this way, can reduce the impact to the electric wire netting and pipe network. What merits attention is two pump when frequency conversion and worker are switched over frequently, have procedure it locks to be enough each other only, outputting must adopt machinery to interlock the contactor, can avoid the situation that two contactors close at the same time in the twinkling of an eye in this way, so as not to short out in twinkling of an eye causing power. Pressure sensor P monitors the size of the water pressure signal in real time, the signal is dealt with by PID, input it to the frequency converter. At the small flow, water pump electrical machinery 1M turn round (whether 1KM1 is it shut to suck), and through feedback password change his rotational speed constantly, it is invariable in order to keep the pressure; In case of large flow , compare frequency conversion by pressure circuit send out through PLC " constant/changed switch over frequently" " operate and interlock " the order, machinery interlocks the contactor ( 2KM2 in 2KM (2KM1 +2KM2 ), contactor 3KM have the electricity. At this moment, electrical machinery 2M is started by way of frequency conversion, 1M is switched over and run at full speed frequently to run. In this way, this system can maintain water consumption on a invariable pressure all the time. Built up in the aforesaid district initial stage, supply water and adopt the way frequently of workers, because of energy consumption being heavy dependability is bad, the household reflects strongly. Use instead after frequency conversion supply water, installation total capacity reduce 25% than original equipment, economize on electricity the index is close 30% synthetically actually, the result is remarkable.3、Several questions while apply are in case of great majorityThe environment for use of the scene is comparatively abominable. Though frequency converter has very strong protection functions itself, such as owe keep , excessive pressure , is it flow to pass, electric current amplitude limiting is it make exactly to choose, overload, overheated lacking looking , shorting out and disconnected ink protect the function But must prevent trouble before it happens . Through using finding, two kinds of brands of Mitsubishi, Fuji, because has fully considered various kinds of abominable running environment in design andmanufacture. The dependability and service life under the same condition are higher than some brands. One small city of mountain area of west place in Hubei in Hubei, average 1200m above sea level, the humidity on the high side of long-term most of the time (about 80%), the sulfur dioxide is seriously polluted, a set of frequency conversion that one factory produces supplies water of the equipment, because has not considered above-mentioned factors, less than one year, the relevant parts of the equipment are corroded seriously. And the like product which we designed, installed in the same area, because has fully considered the situations of different difference, on the selecting types of the equipment and component, have adopted the ship standard. Through the use of more than two years, ran well, stood the tests of different sternness. Find in using actually, the frequency converter itself is that a strong interference takes place in the source, will often influence the normal running of the equipment. Especially when the low rotational speed of the water pump operates, the frequency shown on the frequency converter does not correspond to actual operation frequency. Generally there are two kinds of spread ways to interfere: The circuit bunch is disturbed and space radiation is interfered. Can take the corresponding measure to solve according to the actual conditions of the scene. For example is it strain wave and absorb the return circuit to increase to programmable power end of controller, PID regulator introduction of unit output sure to have reliable shielding, link frequency converter, ground terminal of electrical machinery with earth stake firmly, control the line and motive force line leave certain distance, in order to strengthen and resist the electromagnetic ability to interfere. Only in this way, can make system keep the long and steady working state in high temperature, humidity, mould, strong harsh terms of interfering etc.4、ConclusionsAre by way of adjusting the speed as the central water supply in frequency conversion, the result is obvious to economize on water, economize on electricity, can be extensively suitable for 20-10000 residents the biotope, skyscraper, hotels and restaurants, fire control or district pressurize and supply water, it is ideal facilities that the medium and small- scale waterworks supplied water too. Its amount of water quality supported is high, the economic benefits are obvious, the social benefit is enormous, with the development of national economy and constant improvement of the living standards of the people, it is sure to be used and popularized progressively in our country5、List of referencesZhang Wanzhong, Zhu Jie, Wang Mingquan. A kind of new-type frequency conversion constant pressure supplies water of the plan of design of the pump station. Electrical age, 1999 (10): 22-232Liu YingChun. Principle design of the sensor and application. Beijing: University of Science and Technology of the national defense publishing Press, 1989.59-623Lu Guangda. Electric installation project manual of the building. Beijing: The electric publishing house of water conservancy, write the group in 1995.222- 2244"Theautomatic projecting ". Give and drain off water the automatic project. Beijing: The electric publishing house of water conservancy, 1997.301-312。