Design Analysis of Multiphase DC Chopper Motor Drive

DC chopper propulsion speed control is attained by a solid-state switch whose variable on-off duty cycle transfers a proportional quantity of pulsed energy into a motor. The pulsed battery current is alternately stored and expended within the dc motor and its series connected dc choke during each period of conduction and succeeding freewheeling operating mode. Hence an energy transfer is maintained transforming a high voltage low dc supply into a lower voltage higher dc demanding load. The transformation ratio is considered a controlled variable by simply controlling the on-off conduction duty cycle of its solid-state switch. This simplistic approach, however, fails to recognize that the instantaneous battery current amplitude equals the motor current demand during the switch ``on´´ period resulting in potentially very large peak power demands [1].