| 摘要 |
PURPOSE:To restrict an overcurrent which flows when a main motor is inversely energized, only by adding a converter which converts the negative output of a DCCT circuit into a positive output to a commutation failure detector which detects the commutation failure of a chopper. CONSTITUTION:The chopper, which controls the regenerative braking, is provided with the commutation failure detector CED to protect the main motor from the commutation failure of the chopper in a closed circuit, namely, from the forward overcurrent. The detector CFD functions to trip a high-speed current reducer HB2 immediately after the commutation failure to shorten the time lasting to the circuit breaking and prevent the abnormal current from increasing. An operational amplifier OA containing diodes D1, D2 and an amplifier A is added to the DCCT circuit 2, which belongs to the detector CFD and generates a positive or negative output in instantaneous response to a current picked up by a current transformer 1. |
