| 摘要 |
PURPOSE:To lower cost by eliminating necessity of providing an over-load protection exclusive circuit, by providing a secondary resistance control circuit of a motor having an over-load protective characteristic. CONSTITUTION:Current of a main circuit 1 of an induction motor 9 is detected by CT 3, the voltage conversion is made by a converter 5, and to the respective sensitivity areas of an over current protecting relays 4 of different characteristics, a command is given to a forward-reversal commanding device 7 or 8 of a control motor 13 which changes resistance value of a liquid resistor 12. Depending on magnitude of load torque at this time, the motor 9 becomes nonoperative at the point of exceeding the output limit torque of the motor. And therefore, by driving the control motor 13 at the point where the output torque is smaller than the output limit torque of the motor, resistance value of the liquid resistor 12 is changed, and load torque of the motor 9 is controlled. |
