| 摘要 |
PURPOSE:To prevent faulty detection due to the change of a current voltage in a main circuit, by changing a non-detecting time in accordance with the voltage of a voltage source. CONSTITUTION:A voltage type inverter is constituted of a filter reactor 2, a filter capacitor 3, thyristors 4a-4b and a voltage detector 5 to supply an electric power to a load 6. In this case, filter capacitor voltage detector 21 is connected to both terminals of the filter capacitor 3 in parallel to detect a voltage (voltage source voltage). The time width of a variable detecting time signal is shortened upon increasing the voltage of the filter capacitor while the time width of the same signal is lengthened upon decreasing the same voltage. As a result, the short-circuit of phases may be detected quickly when the voltage of the filter capacitor is high and the rush current upon the short- circuit of the phase is large while the detection may be effected slowly when said voltage is low and the the superposing commutation of the current is long.
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