Development of Two Novel Power Electronic Circuits for Dynamic Braking of Motors

Abstract

The goal of this study was to develop two dynamic braking schemes for a triac voltage-controlled variable-speed motor. In the beginning, it is proposed to operate the AC voltage controller as a half-wave-controlled AC-to-DC converter by inhibiting firing pulses to the triac in one half-cycle of supply voltage so that dynamic braking can be affected. It is found that such an attempt has failed, and during half-wave-controlled converter operation, the motor runs at very low speed. The causes of the failure are investigated, and then two power electronic circuits capable of affecting dynamic braking of motors with a half-wave-controller-fed operation are proposed. The first circuit employs controlled free-wheeling across the motor terminals, and the second method uses disconnection of auxiliary winding. Both methods are shown to achieve dynamic braking of the motor. Simulated and measured results are presented to show the effectiveness of the two circuits.