| 摘要 |
PURPOSE:To discriminate surely the operating state at no load and a fault of an element by inputting an output signal of a voltage detector connected between an anti- series connecting point of a bipolar semiconductor circuit breaker and a connecting bus of a power and a load and an open/close command signal of the bipolar semiconductor circuit breaker so as to detect the operating state of the bipolar semiconductor circuit breaker. CONSTITUTION:When the bipolar semiconductor circuit breaker 11 is brought into the non-conductive state while a current flows from a DC power supply 1 to a load 3 and from the load 3 to a regenerative inverter 9, since an output of a voltage detector 12 is zero when the semiconductor circuit breakers 2, 2a are normal, the non-conductive state is detected by comparing the output with an open/close command at an operating state detection circuit 7. When the load current is zero and the bipolar semiconductor circuit breakers are opened by the open/close command, and if an element fault of the 1st semiconductor circuit breaker 2 and interruption fault take place, the voltage detector 12 detects the voltage of the DC power supply 1, and while an element fault or interruption fault of the 2nd semiconductor circuit breaker 2a takes place on the other hand, the voltage detector 12 detects a cunter electromotive force of the load 3.
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