Analysis on the failure of dynamic braking of capacitor-run induction motor supplied from half-controlled converter

This paper examines the viability of applying dynamic braking to AC voltage controller supplied capacitor-run induction motor. During the variable speed operation, the AC voltage regulator is gated during both half-cycles of the supply voltage. It is proposed to effect dynamic braking of the motor by inhibiting firing pulses during the negative half-cycles of the supply voltage. This will lead to half-controlled converter operation applying DC voltage across the motor terminals, and is supposed to cause dynamic braking. Contrary to expectation, motor is observed to rotate at a very low speed instead of braking. Theoretical, computed and measured results are presented in this paper to explain the failure of dynamic braking.