PC BASED P.W.M. INVERT FED INDUCTION MOTOR DRIVE USING SPACE VECTOR TECHNIQUE

Abstract

This dissertation concerns with the variable frequency operation of a three phase squirrel-cage Induction Motor using PWM VSI employing MOSFET devices. The space vector technique is used for PWM pattern generation having smooth voltage control with variation in frequency. PWM inverter is operated in the overmodulation mode before transition to the six-step mode. The foreground/background approach is used for the calculation of data for 300 space rotation and then symmetrisation is done for complete 3600 pattern. The program is written in "C" language. The PWM signals generated by PC-AT are interfaced to the MOSFET based PWM inverter through an optical isolation circuit. The PWM inverter also incorporates an electronic overcurrent sensing scheme to protect the power devices against overloads. The inverter system developed is first tested on resistive and inductive loads. Then it is used to feed Induction Motor on no load. Waveforms for machine terminal voltage and line current at different frequencies are recorded. Finally, the experimental results at no load and under load conditions are presented