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

1、英文原文Design and Implementation of PLC-Based Monitoring Control System for Induction MotorMaria G. Ioannides, Senior Member, IEEEAbstractThe implementation of a monitoring and control system for the induction motor based on programmable logic controller(PLC) technology is described. Also, the implemen

2、tation of the hardware and software for speed control and protection with the results obtained 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 condit

3、ions. Tests of the induction motor system driven by inverter and controlled by PLC prove a higher accuracy in speed regulation as compared to a conventional V f control system. The efficiency of PLC control is increased at high speeds up to 95% of the synchronous speed. Thus, PLC proves themselves a

4、s a very versatile and effective tool in industrial control of electric drives.Index TermsComputer-controlled systems, computerized monitoring, electric drives, induction motors, motion control, programmable logic controllers (PLCs), variable-frequency drives, voltage control.I. INTRODUCTIONSince te

5、chnology for motion control of electric drives became available, the use of programmable logic controllers (PLCs) with power electronics in 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

6、 the ability to control motors and other equipment with a virtually unity power factor 3. Many factories use PLCs in automation processes to diminish production cost and to increase quality and reliability 49. Other applications include machine tools with improved precision computerized numerical co

7、ntrol (CNC) due to the use of PLCs 10.To obtain accurate industrial electric drive systems, it is necessary to use PLCs interfaced with power converters, personal computers, and other electric equipment 1113. Nevertheless, this makes the equipment more sophisticated, complex, and expensive 14, 15.Fe

8、w papers were published concerning dc machines controlled by 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 self-tuning regulator t

9、echnology 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 position, direction and speed, reducing the number of circuit components, lowering the cost, and enhancing re

10、liability 18. For switched reluctance motors as a possible alternative to adjustable speed ac and dc drives, a single chip logic controller for controlling torque and speed uses a PLC to implement the digital logic coupled with a power controller 19. Other reported application concerns a linear indu

11、ction motor for passenger elevators with a PLC achieving the control of the drive system and the data acquisition 20.To monitor power quality and identify the disturbances that disrupt production of an electric plant, two PLCs were used to determine the sensitivity of the equipment 21.Only few paper

12、s 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 to frequency ratio constant under the whole control conditions 3. The vector control integrated circuit uses a com

13、plex programmable logic device (CPLD) and integer arithmetic for the voltage or current regulation of three-phase pulse-width modulation (PWM) inverters 22. 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 three-phase induction motor. It describes the design and implementation of the confi

15、gured hardware and software. The test results obtained on induction motor performance show improved efficiency and increased accuracy in variable-load constant-speed-controlled operation. Thus, the PLC correlates and controls the operational parameters to the speed set point requested by the user an

16、d monitors the induction motor system during normal operation and under trip conditions.II. PLC AS SYSTEM CONTROLLERA PLC is a microprocessor-based control system, designed for automation processes in industrial environments. It uses a programmable memory for the internal storage of user-orientated

17、instructions for implementing specific functions 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 electrical signals to be interfaced. Input

18、 devices and output devices of the are connected to the PLC and the control program is entered into the PLC memory.In our application, it controls through analog and digital inputs and outputs the varying load-constant speed operation of an induction motor. Also, the PLC continuously monitors the in

19、puts 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 into a proprietary bus: a central processor unit (CPU), a power supply unit, input-output modules I/O, and a program termin

20、al. Such a modular approach has the advantage that the initial configuration can be expanded for other future applications such as multimachine systems or computer linking.III. CONTROL SYSTEM OF INDUCTION MOTORIn Fig. 2, the block diagram of the experimental system is illustrated. The following conf

21、igurations can be obtained from this setup. a) A closed-loop control system for constant speed operation, configured 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.b) An open-loop control

22、system 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.c) The standard variable speed operation. The induction motor drives a variable load and is fed by a constant voltage-constant frequency stan

23、dard three-phase supply. The open-loop configuration b) can be obtained from the closed-loop configuration a) by removing the speed and load feedback. On the other hand, operation c) results if the entire control system is bypassed.IV. HARDWARE DESCRIPTIONThe control system is implemented and tested

24、 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 is connected to a three-phase main switch and then to a three-phase thermal overload relay, which provides

25、 protection against current overloads. The relay output is connected to the rectifier, which rectifies the three-phase voltage and gives a dc input to the insulated gate bipolar transistor (IGBT) inverter. Its technical specifications 25 are summarized in Table II. The IGBT inverter converts the dc

26、voltage input to three-phase voltage output, which is supplied to the stator of the induction motor. On the other hand, the inverter is interfaced to the PLC-based controller. This controller is implemented on a PLC modular system 5, 2628. The PLC architecture refers to its internal hardware and sof

27、tware. As a microprocessor-based system, the PLC system hardware is designed and built up with the following modules 2937: central processor unit (CPU); discrete output module (DOM); discrete input module (DIM); analog outputs module (AOM) analog inputs module (AIM) power supply.Other details of the

28、 PLC configuration are shown in Tables III and IV. 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 loops of the closed-loop system are setup by using the

29、load current sensor, the speed sensor, and the AIM. A tachogenerator (permanent magnet dc motor) is used for speed sensing. The induction machine drives its shaft mechanically and an output voltage is produced, the magnitude of which is proportional to the speed of rotation. Polarity depends on the

30、direction of rotation. The voltage signal from the tachogenerator must match the specified voltage range of the AIM (05 V dc and 200-k internal resistance). Other PLC external control circuits are designed using a low-voltage supply of 24 V dc.For the manual control, the scheme is equipped with star

31、t, 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 switch, an automatic three-phase switch, an automatic single phase switch, a three-phase thermal overload relay, a load automatic switch, sign

32、al lamps (forward, backward, start, stop, trip), push buttons (start, stop, trip), a selector switch (for the forward/backward direction of rotation), a speed selector, a gain selector, as well as the PLC modules and the rectifier-inverter are installed in a control panel. The program is downloaded

33、into the PLC from a personal computer PC and an RS232 serial interface.V. SOFTWARE DESCRIPTIONPLCs programming is based on the logic demands of input devices and the programs implemented are predominantly logical rather than numerical computational algorithms. Most of the programmed operations work

34、on a straightforward two-state “on or off basis and these alternate possibilities correspond to “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 devices. T

35、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, verified, tested, and diagnosed. First, the high-level program is written in ladder di

36、agrams, 33, 34. Then, the ladder diagram is converted into binary instruction codes so that they can be stored in random-access memory (RAM) or erasable programmable read-only memory (EPROM). Each successive instruction is decoded and executed by the CPU. The function of the CPU is to control the op

37、eration of memory and I/O devices and to process data according to the program. Each input and output connection point on a PLC has an address used to identify the I/O bit. The method for the direct representation of data associated with the inputs, outputs, and memory is based on the fact that the

38、PLC memory is organized into three regions: input image memory (I), output image memory (Q), and internal memory (M). Any memory location is referenced directly using %I, %Q, and %M (Table III).The PLC program uses a cyclic scan in the main program loop such that periodic checks are made to the inpu

39、t variables (Fig. 3). The program 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 of the various ladder rungs determine the output

40、states. The updated output states are stored in fixed memory locations (output image memory Q). The output values held in memory are then used to set and reset the physical outputs of the PLC simultaneously at the end of the program scan. For the given PLC, the time taken to complete one cycle or th

41、e scan time is 0, 18 ms/K (for 1000 steps) and with a maximum program capacity of 1000 steps. The development system comprises a host computer (PC) connected via an RS232 port to the target PLC. The host computer provides the software environment to perform file editing, storage, printing, and progr

42、am operation monitoring. The process of developing the program to run 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 PLCs microprocessor and downloading the object code from the PC to the PLC system

43、 via the serial communication port. The PLC system is online when it is in active control of the machine and monitors any data to check for correct operation.PLC Speed Control SoftwareIn Fig. 4, the flowchart of the speed control software is illustrated. The software regulates the speed and monitors

44、 the constant speed control regardless of torque variation. The inverter being the power supply for the motor executes this while, at the same time, it is controlled by PLCs software. The inverter alone cannot keep the speed constant without the control loop with feedback and PLC. From the control p

45、anel, the operator selects the speed setpoint and the forward/backward direction of rotation. Then, by pushing the manual start pushbutton, then the rotation stops. The corresponding input signals are interfaced to the DIM and the output signals to the DOM as shown in Table IV. The AIM receives the

46、trip signal IS from the stator current sensor, 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 speed by the operator and the actual speed o

47、f 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 increases the V/F of the inverter and, as a result, the speed of the motor is corrected.The implemented control is of proporti

48、onal 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 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 gai

49、n KP by using a rotary resistor mounted on the control panel (gain adjust) and the AIM receives its voltage drop as controller gain signal (010 V). The requested speed is selected using a rotary resistor and the AIM reads this signal. Its value is sent to the AOM and displayed at the control panel (

50、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 signal in Newton-meters (N.m). Their corresponding signals are output to the AOM (Table IV).B. Monitor a

51、nd Protection SoftwareDuring motor operation, it is not possible to reverse its direction of rotation by changing the switch position. Before direction reversal, the stop button must be pushed. For motor protection against overloading currents during starting and loading, the following commands were

52、 programmed into the software.i) Forward/backward signal is input to DIM.ii) Speed set point signal nsp , the load current IL , the stator current IS, and the speed feedback signal are input to AIM.iii) At no load IS , if the speed set point is lower than 20% or nsp300 r/min, the motor will not star

53、t.iv) At an increased load over 0, 4 N m (40% of rated torque),IS , and a speed setpoint lower than 40% or nsp600r/min, the motor will not start.v) If the load is increased more than 1, 0N m(rated torque) IS and if the speed set point exceeds 100% or nsp 1500r/min, the motor enters the cutoff proced

54、ure.vi) In all other situations, the motor enters in the speed control mode and the speed control software is executed as described in Subsection A.In Fig. 5, the flowchart of this software is shown.C. Cutoff and Restart Motor SoftwareIn Fig. 6, the flowchart of this software is shown. In overloadin

55、g situations, the motor is cut off and the trip lamp (yellow) is lit. The operator must release the thermal relays and then must turn 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. The mo

56、tor can be cut off by the operator 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. The load must be disconnected immediately after the motor cuts off and before the drive system is re

57、started. The motor will not start before 3 s after cutoff even if the start button is pushed.中文譯文基于PLC的異步電動機監(jiān)控系統(tǒng)的設(shè)計及應用主著：Maria G. Ioannides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)的正常運行和跳閘情況。實驗說明用逆變器驅(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

58、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。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。.簡介自從電力拖動運動控制技術(shù)出現(xiàn)，在電器方面得到應用的用電力電子器件實現(xiàn)的可編程邏輯控制器PLC也應用到生產(chǎn)自動化方面。這種應用的優(yōu)點是：比方啟動時低電壓下滑，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)本錢且提高了質(zhì)量和可靠性。PLC還應用到計算機數(shù)值控制CNC的改進精度的機床上。將PLC與電

59、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)備更復雜更昂貴。 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方法，和把基于自我調(diào)整技術(shù)的自適應調(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，降低線路元件的數(shù)量，減少本錢，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

60、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。只有一少局部文章是介紹PLC在異步電動機上的應用。一個三相異步電動機功率控制器利用PLC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。異步電機的應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控制單元也需要參加到系統(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用。異步電動機實驗說明了在變動負載和恒速的運動情況下功率和精