DC TO AC CONVERTER FOR CONTROLLED DRIVES, BASED ON A NOVEL HIGH EFFICIENCY, HIGH CURRENT TRANSISTOR SWITCH

The possibility of a simplified three phase dc to ac converter for control of squirrel cage machine drives in battery vehicles and industrial drives is discussed. The operational characteristics of this four switch phase asymetric B6 bridge requires both high switching frequency and lower than conventional conduction loss to be exploited further. Higher switching frequencies in the power range up to 60 kVA may be obtained by using bipolar power transistor based switches. The lower conduction loss is achieved by the introduction of compensated darlington power switch technology. The characteristics of a 200 V switch for 60 kVA showing a voltage drop of 200 mV at 300 A, and a fall time of 450 ns, is discussed and the technology evaluated for application to the said dc to ac converters. Total loss characteristics is found to correspond to requirements, and a basis for comparison to other power processing devices is discussed.