| 摘要 |
PURPOSE:To prevent an excitation rush current, by using a voltage phase comparing circuit and a control circuit for generating the same phase voltage as a system voltage detected by a voltage detector. CONSTITUTION:On the secondary side of a power-side breaker 1, an active filter unit 3 is connected to the same bus that is joined with a transformer 2 or connected on the downstream side thereof. The active filter unit 3 includes a voltage detector 4 for detecting a system voltage (Vs) on the primary side of the breaker 1, a control circuit 5 for providing the active filter unit 3 with a voltage of the same phase as that of a system voltage (Vs) detected by a voltage detector 4, a voltage/phase comparing circuit 6 for generating a permission signal to operate the power-side breaker 1 on the condition that the output voltage from the active filter unit 3 is in accord with the system voltage (Vs), and a DC power supply 10. By these means, before the power breaker 1 is turned on, a voltage is applied from a filter unit 3 to a winding of a transformer 2, and a core of the transformer 2 is excited so that a magnetic flux with a lag phase behind the system voltage (vs) by 90 degrees is forcedly generated. |
