| 摘要 |
PURPOSE:To prevent heating of a rush current preventive resistor due to load current, by short-circuiting the rush current preventive resistor at the time of an operation command after making the power source. CONSTITUTION:An operation signal is provided upon elapse of predetermined time after throw-in of a three-phase AC power source 11. Consequently, the operation command and a detection signal (i) from an input voltage detecting circuit 21 are provided to a control circuit 20 so as to bring logical product thereof to '1'. The control circuit 20 operates a switch 18 so as to conduct a semiconductor switch 14. Consequently, a shortcircuit 9 short-circuits a surge preventing resistor 7 thus preventing heating of the surge preventing resistor 7 due to load current when a motor is driven. |
