| 摘要 |
PROBLEM TO BE SOLVED: To quickly interrupt motor drive current by detecting an overload through a current transformer, when a motor is driven and operating a semiconductor switch in a feeder to the motor. SOLUTION: Semiconductor switches 4 and 5 are placed in lines in a phase R and a phase T of lines in phases R, S, and T continuing to a three-phase power supply in the phases R, S, and T. Photocouplers 4a and 5a, comprising a switch control circuit for turning on/off the semiconductor switches 4 and 5, are series-connected between the constant voltage source (voltage Vcc) and the output end of a comparator 33 of a starting circuit 30 and between the constant voltage source and the output end of the comparator 58 of a trip circuit 50.
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