外文翻譯--基于plc的異步電動機監(jiān)控系統(tǒng)的設(shè)計及應(yīng)用

1、<p><b>　　中文4620字</b></p><p><b>　　英文原文</b></p><p>　　Design and Implementation of </p><p>　　PLC-Based Monitoring Control System for Induction Motor</p&

2、gt;<p>　　Maria G. Ioannides, Senior Member, IEEE</p><p>　　IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 19, NO. 3, SEPTEMBER 2004</p><p>　　Abstract—The implementation of a monitoring and c

3、ontrol system for the induction motor based on programmable logic controller(PLC) technology is described. Also, the implementation of the hardware and software for speed control and protection with the results obtained

4、from tests on induction motor performance is provided. The PLC correlates the operational parameters to the speed requested by the user and monitors the system during normal operation and under trip conditions. Tests of

5、the inducti</p><p>　　Index Terms—Computer-controlled systems, computerized monitoring, electric drives, induction motors, motion control, programmable logic controllers (PLCs), variable-frequency drives, vol

6、tage control.</p><p>　　I. INTRODUCTION</p><p>　　Since technology for motion control of electric drives became available, the use of programmable logic controllers (PLCs) with power electronics i

7、n electric machines applications has been introduced in the manufacturing automation [1], [2].This use offers advantages such as lower voltage drop when turned on and the ability to control motors and other equipment wit

8、h a virtually unity power factor [3]. Many factories use PLCs in automation processes to diminish production cost and to increase qual</p><p>　　Few papers were published concerning dc machines controlled by

9、PLCs. They report both the implementation of the fuzzy method for speed control of a dc motor/generator set using a PLC to change the armature voltage [16], and the incorporation of an adaptive controller based on the se

10、lf-tuning regulator technology into an existing industrial PLC [17]. Also, other types of machines were interfaced with PLCs. Thereby, an industrial PLC was used for controlling stepper motors in a five-axis rotor pos<

11、;/p><p>　　Only few papers were published in the field of induction motors with PLCs. A power factor controller for a three-phase induction motor utilizes PLC to improve the power factor and to keep its voltage

12、to frequency ratio constant under the whole control conditions [3]. The vector control integrated circuit uses a complex programmable logic device (CPLD) and integer arithmetic for the voltage or current regulation of th

13、ree-phase pulse-width modulation (PWM) inverters [22]. </p><p>　　Many applications of induction motors require besides the motor control functionality, the handling of several specific analog and digital I/O

14、 signals, home signals, trip signals,On /off/ reverse commands. In such cases, a control unit involving a PLC must be added to the system structure. This paper presents a PLC-based monitoring and control system for a thr

15、ee-phase induction motor. It describes the design and implementation of the configured hardware and software. The test results obtained on</p><p>　　II. PLC AS SYSTEM CONTROLLER</p><p>　　A PLC is

16、 a microprocessor-based control system, designed for automation processes in industrial environments. It uses a programmable memory for the internal storage of user-orientated instructions for implementing specific funct

17、ions such as arithmetic, counting, logic, sequencing, and timing [23], [24].A PLC can be programmed to sense, activate, and control industrial equipment and, therefore, incorporates a number of I/O points, which allow el

18、ectrical signals to be interfaced. Input devices and</p><p>　　In our application, it controls through analog and digital inputs and outputs the varying load-constant speed operation of an induction motor. Al

19、so, the PLC continuously monitors the inputs and activates the outputs according to the control program. This PLC system is of modular type composed of specific hardware building blocks (modules), which plug directly int

20、o a proprietary bus: a central processor unit (CPU), a power supply unit, input-output modules I/O, and a program terminal. Such a modu</p><p>　　III. CONTROL SYSTEM OF INDUCTION MOTOR</p><p>　　I

21、n Fig. 2, the block diagram of the experimental system is illustrated. The following configurations can be obtained from this setup. </p><p>　　a) A closed-loop control system for constant speed operation, co

22、nfigured with speed feedback and load current feedback. The induction motor drives a variable load, is fed by an inverter, and the PLC controls the inverter V/F output.</p><p>　　b) An open-loop control syste

23、m for variable speed operation. The induction motor drives a variable load and is fed by an inverter in constant V/F control mode. The PLC is inactivated.</p><p>　　c) The standard variable speed operation. T

24、he induction motor drives a variable load and is fed by a constant voltage-constant frequency standard three-phase supply. </p><p>　　The open-loop configuration b) can be obtained from the closed-loop config

25、uration a) by removing the speed and load feedback. On the other hand, operation c) results if the entire control system is bypassed.</p><p>　　IV. HARDWARE DESCRIPTION</p><p>　　The control syste

26、m is implemented and tested for a wound rotor induction motor, having the technical specifications given in Table I. The induction motor drives a dc generator, which supplies a variable load. The three-phase power supply

27、 is connected to a three-phase main switch and then to a three-phase thermal overload relay, which provides protection against current overloads. The relay output is connected to the rectifier, which rectifies the three-

28、phase voltage and gives a dc input to the i</p><p>　　? central processor unit (CPU);</p><p>　　? discrete output module (DOM);</p><p>　　? discrete input module (DIM);</p><

29、p>　　? analog outputs module (AOM)</p><p>　　? analog inputs module (AIM)</p><p>　　? power supply.</p><p>　　Other details of the PLC configuration are shown in Tables III and IV. &

30、lt;/p><p>　　A speed sensor is used for the speed feedback, a current sensor is used for the load current feedback, and a second current sensor is connected to the stator circuits [32]. Thus, the two feedback lo

31、ops of the closed-loop system are setup by using the load current sensor, the speed sensor, and the AIM. </p><p>　　A tachogenerator (permanent magnet dc motor) is used for speed sensing. The induction machin

32、e drives its shaft mechanically and an output voltage is produced, </p><p>　　the magnitude of which is proportional to the speed of rotation. Polarity depends on the direction of rotation. The voltage signal

33、 from the tachogenerator must match the specified voltage range of the AIM (0–5 V dc and 200-k internal resistance). Other PLC external control circuits are designed using a low-voltage supply of 24 V dc.</p><

34、p>　　For the manual control, the scheme is equipped with start, stop, and trip push buttons, as well as with a forward and backward direction selector switch. As shown in Fig. 2, all of the described components: a main

35、 switch, an automatic three-phase switch, an automatic single phase switch, a three-phase thermal overload relay, a load automatic switch, signal lamps (forward, backward, start, stop, trip), push buttons (start, stop, t

36、rip), a selector switch (for the forward/backward direction of rota</p><p>　　V. SOFTWARE DESCRIPTION</p><p>　　PLC’s programming is based on the logic demands of input devices and the programs im

37、plemented are predominantly logical rather than numerical computational algorithms. Most of the programmed operations work on a straightforward two-state “on or off” basis and these alternate possibilities correspond to

38、“true or false” (logical form) and “1 or 0” (binary form), respectively. Thus, PLCs offer a flexible programmable alternative to electrical circuit relay-based control systems built using analog d</p><p>　　T

39、he programming method used is the ladder diagram method. The PLC system provides a design environment in the form of software tools running on a host computer terminal which allows ladder diagrams to be developed, verifi

40、ed, tested, and diagnosed. First, the high-level program is written in ladder diagrams, [33], [34]. Then, the ladder diagram is converted into binary instruction codes so that they can be stored in random-access memory (

41、RAM) or erasable programmable read-only memory (EPROM). Eac</p><p>　　The PLC program uses a cyclic scan in the main program loop such that periodic checks are made to the input variables (Fig. 3). The progra

42、m loop starts by scanning the inputs to the system and storing their states in fixed memory locations (input image memory I). The ladder program is then executed rung-by-rung. Scanning the program and solving the logic o

43、f the various ladder rungs determine the output states. The updated output states are stored in fixed memory locations (output image memory Q)</p><p>　　The development system comprises a host computer (PC) c

44、onnected via an RS232 port to the target PLC. The host computer provides the software environment to perform file editing, storage, printing, and program operation monitoring. The process of developing the program to run

45、 on the PLC consists of: using an editor to draw the source ladder program, converting the source program to binary object code which will run on the PLC’s microprocessor and downloading the object code from the PC to th

46、e PLC</p><p>　　PLC Speed Control Software</p><p>　　In Fig. 4, the flowchart of the speed control software is illustrated. The software regulates the speed and monitors the constant speed control

47、 regardless of torque variation. The inverter being the power supply for the motor executes this while, at the same time, it is controlled by PLC’s software. The inverter alone cannot keep the speed constant without the

48、control loop with feedback and PLC. </p><p>　　From the control panel, the operator selects the speed setpoint and the forward/backward direction of rotation. Then, by pushing the manual start pushbutton, the

49、n the rotation stops. The corresponding input signals are interfaced to the DIM and the output signals to the DOM as shown in Table IV. </p><p>　　The AIM receives the trip signal IS from the stator current s

50、ensor, the speed feedback signal from the tachogenerator, and the signal from the control panel. In this way, the PLC reads the requested speed and the actual speed of the motor. The difference between the requested spee

51、d by the operator and the actual speed of the motor gives the error signal. If the error signal is not zero, but positive or negative, then the PLC according to the computations carried out by the CPU decreases or incre&

52、lt;/p><p>　　The implemented control is of proportional and integral (PI) type (i.e., the error signal is multiplied by gain KP, integrated, and added to the requested speed). As a result, the control signal is

53、sent to the DOM and connected to the digital input of the inverter to control V/F variations. At the beginning, the operator selects the gain KP by using a rotary resistor mounted on the control panel (gain adjust) and t

54、he AIM receives its voltage drop as controller gain signal (0–10 V). </p><p>　　The requested speed is selected using a rotary resistor and the AIM reads this signal. Its value is sent to the AOM and displaye

55、d at the control panel (speed set point display). Another display of the control panel shows the actual speed computed from the speed feedback signal. A third display shows the load torque computed from the load current

56、signal in Newton-meters (N.m). Their corresponding signals are output to the AOM (Table IV).</p><p>　　B. Monitor and Protection Software</p><p>　　During motor operation, it is not possible to re

57、verse its direction of rotation by changing the switch position. Before direction reversal, the stop button must be pushed. </p><p>　　For motor protection against overloading currents during starting and loa

58、ding, the following commands were programmed into the software.</p><p>　　i) Forward/backward signal is input to DIM.</p><p>　　ii) Speed set point signal nsp , the load current IL , the stator cu

59、rrent IS, and the speed feedback signal are input to AIM.</p><p>　　iii) At no load IS<1.0A , if the speed set point is lower than 20% or nsp<300 r/min, the motor will not start.</p><p>　　i

60、v) At an increased load over 0, 4 N m (40% of rated torque),IS ≥1.3A, and a speed setpoint lower than 40% or nsp≤600r/min, the motor will not start.</p><p>　　v) If the load is increased more than 1, 0N m(rat

61、ed torque) IS≥1.5A and if the speed set point exceeds 100% or nsp ≥1500r/min, the motor enters the cutoff procedure.</p><p>　　vi) In all other situations, the motor enters in the speed control mode and the s

62、peed control software is executed as described in Subsection A.</p><p>　　In Fig. 5, the flowchart of this software is shown.</p><p>　　C. Cutoff and Restart Motor Software</p><p>　　I

63、n Fig. 6, the flowchart of this software is shown.</p><p>　　? In overloading situations, the motor is cut off and the trip lamp (yellow) is lit. The operator must release the thermal relays and then must tur

64、n off the trip lamp by pushing trip or stop button. The thermal relays are set to the motor rated current 1, 5 A. Following this, the motor can be started again.</p><p>　　? The motor can be cut off by the op

65、erator pushing the stop button: the display of the actual speed is set to zero, the start lamp (green) turns off, and the stop lamp (red) turns on and remains lit for 3 s.</p><p>　　? The load must be disconn

66、ected immediately after the motor cuts off and before the drive system is restarted. The motor will not start before 3 s after cutoff even if the start button is pushed.</p><p><b>　　中文譯文</b></

67、p><p>　　基于PLC的異步電動機監(jiān)控系統(tǒng)的設(shè)計及應(yīng)用</p><p>　　主著：Maria G. Ioannides</p><p>　　摘要：本文主要介紹基于可編程邏輯控制器（PLC）的異步電動機監(jiān)控系統(tǒng)的設(shè)計及實現(xiàn)。同時，在獲得異步電動機運行參數(shù)的前提下，實現(xiàn)了電動機保護和速度控制的硬件和軟件設(shè)計。PLC通過處理用戶要求速度下的電動機運行參數(shù)來監(jiān)視系統(tǒng)的正常運

68、行和跳閘情況。實驗表明用逆變器驅(qū)動且PLC控制的異步電動機系統(tǒng)比傳統(tǒng)的V-F變頻控制系統(tǒng)在速度調(diào)整上有更高的精度。在電機速度高達同步速度的95%時PLC控制的系統(tǒng)的效率增加了。因此，可以說明PLC在電力拖動的工業(yè)控制方面是一個通用且有效的工具。</p><p>　　索引詞——計算機控制系統(tǒng)，計算機監(jiān)控，電力拖動，異步電動機，運動控制，可編程邏輯控制（PLCS），變頻驅(qū)動，電壓控制。</p><

69、p><b>　?、?簡介</b></p><p>　　自從電力拖動運動控制技術(shù)出現(xiàn)，在電器方面得到應(yīng)用的用電力電子器件實現(xiàn)的可編程邏輯控制器（PLC）也應(yīng)用到生產(chǎn)自動化方面。這種應(yīng)用的優(yōu)點是：比如啟動時低電壓下滑，并且能夠通過整功率因數(shù)來控制電機和其它設(shè)備。許多廠家都將PLC運用到自動化過程中，降低生產(chǎn)成本且提高了質(zhì)量和可靠性。PLC還應(yīng)用到計算機數(shù)值控制（CNC）的改良精度的機床上。

70、將PLC與電源轉(zhuǎn)換器、個人計算機、和其它電器設(shè)備接口，可以得到精確的工業(yè)電力拖動系統(tǒng)。然而，這樣也使得設(shè)備更復(fù)雜更昂貴。 </p><p>　　很少有人發(fā)表關(guān)于用PLC控制直流電機的文章。他們都介紹用PLC改變電樞電壓控制直流發(fā)電機/電動機的速度這一模糊辦法，和把基于自我調(diào)整技術(shù)的自適應(yīng)調(diào)節(jié)裝置結(jié)合到工業(yè)PLC中。同時其它類型電機也與PLC接口。因此，工業(yè)PLC也可以控制步進電動機五軸轉(zhuǎn)子的位置、方向和速度，降

71、低線路元件的數(shù)量，減少成本，增強可靠性。開關(guān)磁阻電動機可以選擇用直流或是交流加速驅(qū)動，它是用可實現(xiàn)數(shù)字邏輯的PLC和電源控制器做成的單片邏輯控制器來控制電機的轉(zhuǎn)矩和速度。還有介紹用PLC接收數(shù)據(jù)并控制直線異步電動機驅(qū)動的人員升降機的驅(qū)動系統(tǒng)。用兩個PLC來確定裝置的靈敏度，監(jiān)視電網(wǎng)質(zhì)量和鑒別電設(shè)備帶來的擾動。</p><p>　　只有一少部分文章是介紹PLC在異步電動機上的應(yīng)用。一個三相異步電動機功率控制器利用P

72、LC來提高功率因數(shù)，且通過調(diào)整頻率占空比來調(diào)整電壓。矢量控制集成電路用復(fù)雜邏輯可編程和整數(shù)算法調(diào)整三相PWM逆變器的電壓和電流。</p><p>　　異步電機的應(yīng)用除了包括電機控制功能，還有許多特殊模擬和數(shù)字I/O信號，源信號，跳閘信號，開關(guān)轉(zhuǎn)換信號的處理。在這種情況下，PLC控制單元也需要加入到系統(tǒng)結(jié)構(gòu)中。這篇文章講述了基于PLC的三相電動機監(jiān)督控制系統(tǒng)。它描述了配置的硬件和軟件的應(yīng)用。異步電動機實驗表明了在變

73、動負載和恒速的運動情況下功率和精度都提高了?？傊琍LC控制正常和非正常情況下用戶和監(jiān)控者要求的速度設(shè)定點下的運行參數(shù)。</p><p>　　II．PLC作為系統(tǒng)控制器</p><p>　　PLC是為工業(yè)環(huán)境下自動化生產(chǎn)設(shè)計的基于微處理器的控制系統(tǒng)。它用可編程存儲器作為內(nèi)存儲器來存儲執(zhí)行特殊功能的用戶指令如：算法，計算，邏輯，排序和定時。PLC通過編程可檢測，激活和控制工業(yè)設(shè)備，還匯集很多

74、可輸入電信號的I/O點。輸入和輸出設(shè)備與PLC連接，控制程序存儲在PLC的存儲器里（圖1）。</p><p>　　圖1 PLC 的控制過程</p><p>　　在我們的應(yīng)用中，PLC控制異步電機恒速變負載的邏輯和數(shù)字輸入輸出信號。同樣,PLC連續(xù)的監(jiān)視輸入,根據(jù)控制規(guī)則調(diào)整輸出。PLC是有特殊的硬件板快即模塊組成的標(biāo)準型,它們可以直接插入它們的專屬位子:中央處理器(CPU),供電單元,輸

75、入輸出模塊,終端處理器.這種模塊方法的優(yōu)點是初始配置可以為將來的應(yīng)用擴展,如:多機系統(tǒng)或計算機連接。</p><p>　　III.異步電機的控制系統(tǒng)</p><p>　　圖2是實驗系統(tǒng)的結(jié)構(gòu)圖,系統(tǒng)有以下幾部分組成。</p><p>　　a)恒速閉環(huán)控制系統(tǒng)由速度反饋和負載電流反饋組成。異步電機通過逆變器反饋驅(qū)動變負載,PLC控制逆變器的輸出。</p>

76、<p>　　b)變速開環(huán)控制系統(tǒng).異步電機通過恒定的逆變器反饋驅(qū)動變負載。PLC是沒有靈活性。</p><p>　　圖2 實驗系統(tǒng)電氣原理圖</p><p>　　c)標(biāo)準變速系統(tǒng).由三相標(biāo)準恒壓恒頻電源提供給異步電機來驅(qū)動變負載。閉環(huán)系統(tǒng)b)去掉速度和負載反饋可得到開環(huán)系統(tǒng)a)。另一方面,如果整個控制系統(tǒng)是迂回的，c)系統(tǒng)可以實現(xiàn)。</p><p>&

77、lt;b>　　IV．硬件設(shè)計</b></p><p>　　控制系統(tǒng)是為測試轉(zhuǎn)子損壞的異步電機而設(shè)計的，表I給出了技術(shù)規(guī)范。異步電機驅(qū)動作為變動負載的直流電機。三相電源和三相主開關(guān)聯(lián)接，再和可以保護防止過電流的三相熱繼電器相連。繼電器輸出連接整流器，整流器調(diào)整三相電壓，并且給IGBT逆變器提供直流輸入。它的技術(shù)規(guī)范[25]在表II中給出了概括。</p><p>　　表1 異

78、步電機技術(shù)參數(shù)</p><p>　　表2 逆變器技術(shù)參數(shù)</p><p>　　IGBT逆變器將直流電壓輸入轉(zhuǎn)變成三相電壓輸出，提供給異步電機的定子。另外，逆變器與基于PLC的控制器連接。控制器是在標(biāo)準PLC的基礎(chǔ)上實現(xiàn)的。PLC系統(tǒng)調(diào)用它固有的硬件和軟件。作為基于微處理器的系統(tǒng)，PLC系統(tǒng)硬件是由以下幾個模塊組成：</p><p>　　中央處理單元（CPU）<

79、/p><p>　　數(shù)字輸出模塊（DOM）</p><p>　　數(shù)字輸入模塊（DIM）</p><p>　　模擬輸入模塊（AOM）</p><p>　　模擬輸出模塊（AIM）</p><p><b>　　電源</b></p><p>　　表3—表5給出了PLC的其它詳細的結(jié)構(gòu)。速

80、度傳感器是用于速度反饋，電流傳感器是用于負載電流反饋，第二電流傳感器是連接定子回路。因此，閉環(huán)系統(tǒng)的雙反饋回路是有負載電流傳感器，速度傳感器和模擬輸入模塊組成。測速電動機（永磁電動機）就是速度傳感器。異步電機帶動它的軸機械旋轉(zhuǎn)，輸出一個電壓，電壓的大小與旋轉(zhuǎn)速度成比例。極性取決于旋轉(zhuǎn)方向，測速發(fā)電機的電壓信號必須與模擬輸入模塊的電壓范圍（直流0-5V和電阻200K）匹配。PLC的其它外在控制回路設(shè)計采用低壓直流24V電源。因為手動控制，

81、系統(tǒng)中配置了啟動，停止和急速跳閘按鈕，還有向前向后方向選擇開關(guān)。圖2給出了所有組成；一個主開關(guān)，一個自動單相開關(guān)，一個三相熱繼電器，一個負載自動開關(guān)，信號燈（向前，向后，啟動，停止，跳閘），按鈕（啟動，停止，跳閘），選擇開關(guān)（向前向后旋轉(zhuǎn)），一個速度選擇器，一個增益選擇器，還有PLC模塊和整流逆變器也放置在控制面板上。程序從個人主機上通過RS232總線下到PLC中。</p><p>　　表3 PLC結(jié)構(gòu)配置&l

82、t;/p><p><b>　　V.軟件描述</b></p><p>　　PLC程序是依據(jù)輸入設(shè)備的邏輯要求，程序與其說是體現(xiàn)數(shù)字計算法則不若說主要是體現(xiàn)了邏輯性。許多編制的程序是直接工作在“開或關(guān)”兩種狀態(tài)，并且它們這種交替的形式分別是與“真或假”（邏輯形式）和“1或0”（二進制形式）對應(yīng)的。因此，PLC提供了靈活的可編程選擇形式給用模擬設(shè)備建立的電路傳輸控制系統(tǒng)。編程是

83、采用梯形圖方法。PLC提供了在主機終端可以運行的基于軟件的設(shè)計環(huán)境，它可以將梯形圖調(diào)出，修改，測試和診斷。首先，高級程序是用梯形圖來表示。然后，梯形圖轉(zhuǎn)化成二進制命令形式，因此它就可以保存到隨機存儲器（REM）或可擦可編程存儲器（EPROM）。每一個正確的指令都被CPU解碼和執(zhí)行。CPU的功能就是控制存儲器和I/O設(shè)備，依照程序來處理數(shù)據(jù)。每一個PLC上的輸入輸出連接點都一個地址，用來識別輸入輸出位。輸入輸出數(shù)據(jù)和存儲器之間的直接聯(lián)系是

84、以下面的結(jié)構(gòu)為基礎(chǔ)的：PLC的存儲器分為三個區(qū)：輸入映像區(qū)（I），輸出映像區(qū)（Q），和內(nèi)存（M）。任何存儲區(qū)都直接用%I，%M，%Q調(diào)用（表III）。PLC程序在主循環(huán)程序中采用循環(huán)掃描，如對輸入變量的周期檢查。程序先開始掃描系統(tǒng)輸入，然后將它們的狀態(tài)存儲到</p><p>　　掃描程序，處理梯形行各種邏輯運算來決定輸出狀態(tài)。最新的輸出狀態(tài)保存到固定存儲區(qū)（輸出映像區(qū)Q）。輸出數(shù)據(jù)保存在存儲器中，然后在本次程序掃

85、描的最后設(shè)置或是重置輸出設(shè)備。對于給定的PLC，完整的掃描一次所用的時間或是掃描時間是0.18ms/k(1000步)，最大的程序容量是1000步。擴展系統(tǒng)由主機通過232總線連接PLC組成。主機給程序文檔編輯，保存，打印和程序執(zhí)行監(jiān)控提供了軟件環(huán)境。PLC執(zhí)行程序的過程包括：編輯員畫出源梯形程序，將源程序轉(zhuǎn)變成二進制命令形式，這樣它可以在PLC的微處理器中執(zhí)行并通過連續(xù)傳輸端口從PC中下載到PLC系統(tǒng)。當(dāng)PLC系統(tǒng)處于對機器的實時控制時

86、，PLC系統(tǒng)是在線的且監(jiān)控所有數(shù)據(jù)確保正確的運行。</p><p>　　表5 PLC模塊和I/O設(shè)定</p><p>　　A.PLC速度控制軟件</p><p>　　在圖4中，給出了速度控制軟件的流程圖。軟件調(diào)整速度監(jiān)視定速度控制而不管轉(zhuǎn)矩變化。逆變器這會兒在做電機的電源的同時也受到PLC軟件的控制。如果沒有PLC和反饋控制環(huán)，逆變器也不可能控制電機恒定速度運行。操

87、作員通過控制面板設(shè)定速度和選擇電機向前或是向后的旋轉(zhuǎn)方向。通過按下手動按鈕，電機開始旋轉(zhuǎn)。如果停止按鈕被按下，則電機停下。如表5所示，對應(yīng)的輸入信號接入到數(shù)字輸入模塊，輸出信號送到數(shù)字輸出模塊。模擬輸入模塊接受定子電流傳感器的跳閘信號Is，測速發(fā)電機的速度反饋信號，和控制面板的信號。這樣，PLC可以獲得電機被要求的速度和的實際速度。操作員要求的速度和電機實際速度的差值給出了誤差信號。如果誤差信</p><p>　

88、　號不是0，而是正或是負，然后，PLC根據(jù)CPU的運算減少或增加逆變器的V/F，因此，電機速度是修正的?？刂破鞑捎帽壤e分型（PI）（如，誤差信號通過增益放大，積分，加給要求的速度）。最后，控制信號送給數(shù)字輸出模塊，并且連接逆變器的數(shù)字輸入去控制變化量。在開始的時候，操作員通過控制面板上的旋轉(zhuǎn)變阻器改變增益（增益調(diào)節(jié)），模擬輸入模塊接受它的電壓降作為控制增益信號（0-10V）。要求的速度是通過改變旋轉(zhuǎn)變阻器得到的，AIM獲取這個信號。它

89、的值送到AOM，并在控制面板上顯示（設(shè)定速度顯示），控制面板上另一個是顯示通過速度反饋信號計算出的電機實際速度。第三個顯示的是通過負載電流信號計算出來的負載轉(zhuǎn)矩（Nm）。它他們對應(yīng)的信號輸出給AOM。</p><p>　　圖3. 主程序流程圖</p><p>　　圖4 速度軟件流程圖</p><p><b>　　B.監(jiān)測和保護軟件</b>&

90、lt;/p><p>　　圖5給出了軟件流程圖.在電機運行中，不能通過改變開關(guān)位置來改變旋轉(zhuǎn)方向。只有按下停止按鈕才可改變旋轉(zhuǎn)方向。在軟件中編制下列程序,使電機在啟動和帶載運行情況下進行過載電流保護。</p><p>　　I）在DIM中輸入前向后向信號。</p><p>　　II）在AIM中輸入速度設(shè)定值n,負載電流，定子電流，和速度反饋信號。</p>&l

91、t;p>　　III）在無載情況1.0A,如果速度設(shè)定值小于20%,或n<300r/min,電機不會啟動。</p><p>　　IV）負載增加0.4NM(額定轉(zhuǎn)矩的40%),1.3A,速度設(shè)定值低于40%或n<600r/min,則電機不會啟動。</p><p>　　V）如果負載增加1.0NM(額定轉(zhuǎn)矩), 1.5A并且如果轉(zhuǎn)速設(shè)定值超過100%或n1500r/min,電機進

92、入停機程序。</p><p>　　VI）在所有其他情況下,電機進入速度控制模式，速度控制軟件如A部分描述的執(zhí)行。</p><p>　　圖5 監(jiān)視和保護軟件流程圖</p><p><b>　　關(guān)機和重啟電機軟件</b></p><p>　　在圖6給出了軟件流程圖。在過載情況下，電機停機,跳閘燈(黃)亮.操作員必須釋放熱繼電

93、器,然后通過按下跳閘或停止按鈕關(guān)掉跳閘燈。熱繼電器設(shè)定為電機額定電流值1.5A。這樣電機可以重新啟動。</p><p>　　操作員可以按下停止按鈕來停止電機:顯示的實際速度變?yōu)榱?,啟動燈(綠)關(guān)閉，停止燈(紅)閉合且持續(xù)亮3S。</p><p>　　電機停止后和驅(qū)動系統(tǒng)重啟前負載馬上卸下。 即使啟動按鈕已經(jīng)按下,電機在停止后,3秒鐘之內(nèi)不能啟動。</p><p>