Abstract

Adjustable speed induction motor drives are used more and more often in industry, particularly as an energy saving measure. Due to the presence of the power electronic drives, nonsinusoidal waveforms, are injected into the electric distribution and the motor, affecting both the motor and the other loads connected to the same bus. In addition, the output voltage waveform of the converter feeding the motor has adverse effects on its insulation, particularly when long supply cables are used. This thesis is a contribution to the study of these problems, associated with the use of adjustable speed drives. The motor drive circuit characteristics are studied when the speed of the motor is controlled using a pulse width modulated (PWM) inverter. The influence of cable length and power semiconductors switching times on motor overvoltages are studied for different rise times and cable lengths. Simulation studies are carried out using the EMTP software package. Simulation results are verified experimentally.