| 摘要 |
PURPOSE:To prevent an adverse effect on a control circuit caused by operation of a dynamic brake by making the rate of change of the conduction ratio of a chopper at the time of ending dynamic braking smaller than that at the time of starting the dynamic braking. CONSTITUTION:When a voltage on the input side of a control circuit 30 exceeds a set voltage, a current flows through a resistance element 18 by chopping of a chopper 20, power accompanying the power generation of a motor 32 is supplied to the resistance element 18 via the control circuit 30, and power by the power generation is consumed by the resistance element 18. In this case, the rate of change of the conduction ratio of the chopper 20 is made smaller so that the voltage of filter circuits 14, 26, 16, 28 lowers gradually when the chopper 20 is turned OFF. As a result, the oscillation of the voltage of the filter circuits 14, 26, 16, 28 by operation of a dynamic brake is suppressed and a change from dynamic braking to regenerative braking is conducted smoothly. Thus, it is possible to prevent an adverse effect on the control circuit 20 by operation of the dynamic brake. |
