Voltage Clamping Circuits for CSI/IM Drives

One of the limitations of conventional autosequentially commutated inverter (ASCI) for high-power induction motor drives is the high voltage that is produced in the commutation capacitors during the current commutation from one phase to another. Since the capacitor voltage appears directly on the semiconductor components, it increases their required voltage ratings. Also, the high-voltage spikes generated at the motor terminals may cause damage to the motor insulation. A brief review of the literature on limiting the capacitor voltage and clamping the voltage spikes is given. Two circuits suitable for high-power applications are proposed. The analysis and the results of digital computer simulation of the proposed circuits are presented.