外文翻译-变频调速技术在风机、泵类中的应用分析

Frequency conversion transfer speed technology application of air

blower, pump type analyze

In industrial production and processing and manufacturing industry of the products, air blower, pump apparatus are in extensive application range; Its electric energy is consumed to account for with throttle loss and safeguarding, maintenance cost such as valve, relevant apparatus of guard 7%~25% of the production cost, it is a sum of big production expenses. With the deepening constantly of economic reform, the constant aggravation of the market competition; saving energy and reducing the cost has already become and reduced the production cost, raised one of the important means of product quality.

And the frequency conversion that developed at the beginning of the eighties adjusts speed technology, it is exactly the requirement for complying with development of industrial production automation, open a brand-new intellectual electrical machinery era. Change the outmoded mode that the ordinary motor can only be operated by way of making the speed, make motor and pull load can according to produce technological requirement adjust rotational speed export on condition that needn't have any change, thus reduce the consumption of the electrical machinery and achieve the goal that the system is operated high-efficiently.

At the end of the eighties, this technology was introduced to our country and popularized. Have already got practical application in the electrical machinery transmission apparatus in many kinds of trades such as the electricity, metallurgy, petroleum, chemical industry, papermaking, food, textile now. At present, frequency conversion adjusts a main developing direction that speed technology has already become modern electric transmission technology. Remarkable adjusting speed performance, prominent result of economizing on electricity, improve the operation operating mode of the existing equipment, improve systematic safe reliability and utilization rate of equipment and installations, lengthen advantages such as the service life of apparatus, etc. and get abundant embodiment with constant enlargement of the application.

Usually used mainly in the boiler and burn occasions such as system, drying system, cooling system, ventilating system, etc. in the industrial production, apoplexy machine apparatus of processing and manufacturing industry of products, control and regulate indexes such as pressure of burner hearth, wind speed, wind amount,

temperature, etc. so as to meeting the needs of craft and operation operating mode according to the need of producing. The most frequently used control means is to regulate the air door, size of making degree of guard to adjust the controlled target. In this way, no matter the demand size of production, the air blowers should all operate at full speed, but the change of the operation operating mode makes energy consume with the throttle losses of air door, guard. In process of production, not only control the precision and is limited but also cause a large amount of energy to waste losing with the apparatus. Thus lead to the fact the production cost increases, the service life of apparatus is shortened, the plant maintenance, maintenance cost can not be ranked.

The pump apparatus has broad application space on the production field too, propose water pump station, pond store pot give system of arranging, industry water circulatory system, hot exchange system use centrifugal pump, axial-flow pump, gear wheel pump, column fill in apparatus such as the pump Moreover adopt, adjust according to different production demand valve, reflux valve, stop valve, etc. reduce expenditure apparatus carry on flow, pressure, water level control of signal often. In this way, not merely cause a large number of energy to waste, the destruction of sealing properties such as the pipeline, valve, etc.; also accelerate wearing and tearing and vapors of the pump, body of valve and lose, damage the apparatus, influence production, jeopardize product quality when being serious.

Most of air blower, pump apparatus adopt the way in which the asynchronous motor drive directly and run, store in and start the electric current greatly, machinery is assaulted, protect the bad shortcoming of the characteristic electrically. Not only influence by apparatus service life, but also not at load can twinkling of an eye movement protect by apparatus, often present the pump and damage the phenomenon that the electrical machinery is burnt too at the same time.

In recent years, for the energy-conserving urgent need and requirement for improving constantly in product quality, in addition the adoption frequency conversion governor (abbreviated as the frequency converter) is easy to use, non-maintaining and controlling the precision high, and can realize the high functional characteristic; Therefore the scheme of adopting the frequency converter and driving begins to replace the control scheme of air door, guard, valve progressively.

The basic principle of adjusting speed technology of frequency conversion is to

import the relation that frequency is directly proportional to according to rotational speed and working power of electrical machinery: n =60f (1-s) / p, (n, f, s, p show the rotational speed, input frequency, electrical machinery and transfer to difference rate, electrical machinery magnetic pole logarithm respectively in type); Achieve the goal of changing the rotational speed of the electrical machinery through changing the motor working power frequency. The frequency converter is on the basis of principle described above adopts handing in - straight - hand in the power and vary technology, electric electron, microcomputer are controlled, etc. the comprehensive electric products that technology is all over.

Can know through the hydro mechanical philosophy: Air blower, pump apparatus belong to the torque load of square, its rotational speed n and flow Q, pressure H and power P of axle have the following relations: Q ∝ n, H∝ n2, P∝ n3;

I.e., the flow is proportional to rotational speed, the pressure is proportional to the square of rotational speed, the axle power is proportional to the cube of rotational speed.

Take a water pump as an example, its export presses the head for H0 (export presses the quiet pressure difference that the head i.e. entry to the pump and pipeline exports), the specified rotational speed is n0, it is r0 that the tube when the valve is made completely hinders the characteristic, under the specified operating mode and its corresponding pressure is H1, it is Q1 to export the flow.

In controlling at the scene, usually adopt the water pump to operate and export the valve to control the flow rapidly definitely. When the flow reduces 50% to Q2 from Q1, valve turn on degree reduce, make pipe network drag characteristic turn r0 into r1, systematic operating point order, move, order along direction me from original A to B; The pressure H1 of function reduced expenditure by it turns into H2. Water pump axle power actual value can by the formula: P =Q* H/ (η c* η b) *10-3 is obtained. Among them, P, Q, H, η c, η b express the power, flow, pressure, water pump efficiency, transmission device efficiency respectively, transmit as 1 directly. Suppose the total efficiency (η c* η b) 1, water pump order, move, order work, from A to B then, consumption that electrical machinery save for AQ1OH1 and area of BQ2OH2 bad. If adopt and adjust rotational speed n that the speed means changes the water pump, when the flow is reduced from Q1 by 50% to Q2, pipe network drag characteristic the same curve r0 then, systematic operating point order, move, order

along direction II from original A to C, the operation of the water pump is also more rational. All open in the valves, there are only pipe networks.

Under the situation of resistance, the system meets the flow requirement of the scene, energy consumption certainly will be reduced. At this moment, the consumption that the electrical machinery saves is bad for the area of AQ1OH1 and CQ2OH3. Degree is regulated and the rotational speed of water pump is controlled to relatively adopt the valve to be driven, obviously use the rotational speed of the water pump to control more valid and more reasonable, have prominent energy-conserving results.

In addition, valve make systematic pressure H rise regulate, this transform to pipeline and sealing property of valve into, threaten and destroy; And when the rotational speed is regulated, the systematic pressure H will be reduced with reducing of the rotational speed n of the pump, so will not exert a bad influence on the system.

It is easy to obtain from the comparison above: When demand for the flow of the water pump is dropped from 100% to 50% at the scene, adopt the rotational speed to regulate and regulate the power size corresponding to save BCH3H2 than the original valve, the energy-conserving rate is above 75%.

Similar to this, adopt frequency conversion transfer speed technology change pump type, air blower apparatus rotational speed come, control on-the-spot pressure, temperature, water level, etc. other course control the parameter, can control the characteristic and draw out the curve of relation and obtain the comparative result described above according to the system too. Namely adopt frequency conversion transfer speed technology change electrical machinery method of rotational speed, than adopt valve, guard regulate economic for energy-conservation, the apparatus operation operating mode will be obviously improved too.

变频调速技术在风机、泵类中的应用分析

在工业生产和产品加工制造业中，风机、泵类设备应用范围广泛；其电能消耗和诸如阀门、挡板相关设备的节流损失以及维护、维修费用占到生产成本的7%~25%，是一笔不小的生产费用开支。随着经济改革的不断深入，市场竞争的不断加剧；节能降耗业已成为降低生产成本、提高产品质量的重要手段之一。

而八十年代初发展起来的变频调速技术，正是顺应了工业生产自动化发展的要求，开创了一个全新的智能电机时代。一改普通电动机只能以定速方式运行的陈旧模式，使得电动机及其拖动负载在无须任何改动的情况下即可以按照生产工艺要求调整转速输出，从而降低电机功耗达到系统高效运行的目的。

八十年代末，该技术引入我国并得到推广。现已在电力、冶金、石油、化工、造纸、食品、纺织等多种行业的电机传动设备中得到实际应用。目前，变频调速技术已经成为现代电力传动技术的一个主要发展方向。卓越的调速性能、显著的节电效果，改善现有设备的运行工况，提高系统的安全可靠性和设备利用率，延长设备使用寿命等优点随着应用领域的不断扩大而得到充分的体现。

通常在工业生产、产品加工制造业中风机设备主要用于锅炉燃烧系统、烘干系统、冷却系统、通风系统等场合，根据生产需要对炉膛压力、风速、风量、温度等指标进行控制和调节以适应工艺要求和运行工况。而最常用的控制手段则是调节风门、挡板开度的大小来调整受控对象。这样，不论生产的需求大小，风机都要全速运转，而运行工况的变化则使得能量以风门、挡板的节流损失消耗掉了。在生产过程中，不仅控制精度受到限制，而且还造成大量的能源浪费和设备损耗。从而导致生产成本增加，设备使用寿命缩短，设备维护、维修费用高居不下。

泵类设备在生产领域同样有着广阔的应用空间，提水泵站、水池储罐给排系统、工业水（油）循环系统、热交换系统均使用离心泵、轴流泵、齿轮泵、柱塞泵等设备。而且，根据不同的生产需求往往采用调整阀、回流阀、截止阀等节流设备进行流量、压力、水位等信号的控制。这样，不仅造成大量的能源浪费，管路、阀门等密封性能的破坏；还加速了泵腔、阀体的磨损和汽蚀，严重时损坏设备、影响生产、危及产品质量。

风机、泵类设备多数采用异步电动机直接驱动的方式运行，存在启动电流大、机械冲击、电气保护特性差等缺点。不仅影响设备使用寿命，而且当负载出现机械故障时不能瞬间动作保护设备，时常出现泵损坏同时电机也被烧毁的现象。

近年来，出于节能的迫切需要和对产品质量不断提高的要求，加之采用变频调速器（简称变频器）易操作、免维护、控制精度高，并可以实现高功能化等特点；因而采用变频器驱动的方案开始逐步取代风门、挡板、阀门的控制方案。