| 摘要 |
PURPOSE:To check the normality of a switch element even in the conducting condition of a switch by turning off a semiconductor switch for a very short period during the conducting period and discriminating an abnormal condition with the voltage of both edges of the then semiconductor switch. CONSTITUTION:At the zero point of the current to flow at a semiconductor switch 3, the action of gate ignition signal generating circuits 4a and 4b is stopped and a voltage detecting circuit 8 measures the voltage at both edges of the semiconductor switch 3 and the abnormality is detected. At the time point a little later than the zero point of the current to flow at the semiconductor switch 3 at the time of the normality, the gate ignition signal generating circuits 4a and 4b are controlled, the supply of the gate ignition signal to the semiconductor switch 3 is restarted, and when the abnormality is detected, a trouble signal is outputted. Thus, even when the thyristor switch is in the conducting condition, it can be discriminated whether the thyristor is normal or abnormal.
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