基于PLC的恒压供水系统设计 英文资料.doc
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1、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 principle and systems structure of automatic water supply system by using frequency conversion speed regulation in detail. Then th
2、e systems 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
3、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 freq
4、uency 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
5、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-cons
6、erving 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 =
7、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
8、 respectively. According the above: H1/H2 = (f1/f2)2.Namely 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 streng
9、th 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 regula
10、tor 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 a
11、mount 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 charac
12、teristic 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 spee
13、d is 70% oclock of specified rotational speed, the power consumption of the governor is 0.73 =0.343, account for specified 35%. That is to say , 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 backs
14、et 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、CaseanalysesConstant pressure is it regulate flow of
15、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
16、 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
17、increment type or the position type, its total mark one will fetch the cistern , water pump group and complement the fittings to 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
18、 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
19、 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 , t
20、here 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 an
21、d 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
22、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 frequ
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