1、PDF外文：http:/ 4620 字 英文原文 Design and Implementation of PLC-Based Monitoring Control System for Induction Motor Maria G. Ioannides, Senior Member, IEEE IEEE TRANSACTIONS ON ENERGY CONVERSION, VOL. 19, NO. 3, SEPTEMBER 2004 AbstractThe implementation of a monitoring and control system
2、 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 from tests on induction motor performance is provided. The PLC correlates the operational par
3、ameters to the speed requested by the user and monitors the system during normal operation and under trip conditions. 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 efficie
4、ncy of PLC control is increased at high speeds up to 95% of the synchronous speed. Thus, PLC proves themselves as a very versatile and effective tool in industrial control of electric drives. Index TermsComputer-controlled systems, computerized monitoring, electric drives, induction motors, motion c
5、ontrol, programmable logic controllers (PLCs), variable-frequency drives, voltage control. I. INTRODUCTION Since technology for motion control of electric drives became available, the use of programmable logic controllers (PLCs) with power electronics in electric machines applications has been intro
6、duced 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 with a virtually unity power factor 3. Many factories use PLCs in automation processes to diminish production cost and to increase qua
7、lity and reliability 49. Other applications include machine tools with improved precision computerized numerical control (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 e
8、lectric equipment 1113. Nevertheless, this makes the equipment more sophisticated, complex, and expensive 14, 15. Few 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
9、change the armature voltage 16, and the incorporation of an adaptive controller based on the self-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
10、 rotor position, direction and speed, reducing the number of circuit components, lowering the cost, and enhancing reliability 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
11、to implement the digital logic coupled with a power controller 19. Other reported application concerns a linear induction 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
12、 production of an electric plant, two PLCs were used to determine the sensitivity of the equipment 21. 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 volta
13、ge 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 three-phase pulse-width modulation (PWM) inverters 22. Many applications of
14、 induction motors require besides the motor control functionality, the handling of several specific analog and digital I/O 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-bas
15、ed monitoring and control system for a three-phase induction motor. It describes the design and implementation of the configured hardware and software. The test results obtained on induction motor performance show improved efficiency and increased accuracy in variable-load constant-speed-controlled
16、operation. Thus, the PLC correlates and controls the operational parameters to the speed set point requested by the user and monitors the induction motor system during normal operation and under trip conditions. II. PLC AS SYSTEM CONTROLLER A PLC is a microprocessor-based control system, designed fo
17、r automation processes in industrial environments. It uses a programmable memory for the internal storage of user-orientated 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 ind
18、ustrial equipment and, therefore, incorporates a number of I/O points, which allow electrical signals to be interfaced. Input devices and output devices of the are connected to the PLC and the control program is entered into the PLC memory. In our application
19、, 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 inputs and activates the outputs according to the control program. This PLC system is of modular type composed of specific hardware bui
20、lding 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 terminal. Such a modular approach has the advantage that the initial configuration can be expanded for other future applications such as mu
21、ltimachine systems or computer linking. III. CONTROL SYSTEM OF INDUCTION MOTOR In Fig. 2, the block diagram of the experimental system is illustrated. The following configurations can be obtained from this setup. a) A closed-loop control system for constant speed operation, configured with spe
22、ed 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 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 standard three-phase supply.
