Microprocessor control system for PWM IGBT inverter feedingthree-phase induction motor

摘要

In this work a three-phase PWM IGBT voltage source inverter hasbeen introduced. The PWM control signals are produced using amicroprocessor, so the complex control circuit hardware of the invertercan be replaced by microprocessor software. The suboptimal PWM switchingstrategy is proposed, which closely approximates and exhibits many ofthe desirable performance characteristics of optimized PWM strategiesbased on minimized total harmonic distortion. The drive system hardwareincludes the implementation of microprocessor system, transistorizedinverter, interface circuits, isolating circuits and driving circuits.The IGBTs are used as efficient switching devices for the inverter powercircuits, so simple and efficient transistor drive circuits can be used.Also, the overlap protection is taken into consideration. The PWMinverter is to feed an induction motor with adjustable voltage tofrequency in a proper relation to maintain approximately constant ratedflux in the machine over the operating frequency range (1-50 Hz). Hence,the drive system is used to control the speed of a three-phase inductionmotor from very low speed to the motor rated speed at a constant torque.The test results were obtained experimentally. The waveforms and thespectrum analysis of PWM control signals are given together with voltageand current of the motor at different frequencies