AUTOMATIC SETTING METHOD OF SLIP FREQUENCY COEFFICIENT

PURPOSE:To correct the variation in the optimum slip frequency upon rising of the temperature of a motor by resetting the slip frequency when the motor reaches the prescribed normal temperature. CONSTITUTION:A mode switching circuit 3, a torque instructing circuit 15, and a slip frequency coefficient arithmetic circuit 16 are provided. A mode switching circuit 3 switches the case that a speed control loop is formed, i.e., the case that the output of an amplifier 2 is applied to a torque limiter 4, the case that a torque is controlled, i.e., the case that the output of a torque instructing circuit 15 is applied to a torque controller 4, and the circuit 15 produces a torque signal of the prescribed value at the mode switching time, and the circuit 16 calculates the optimum slip frequency coefficient in response to the variation in the operating conditions to automatically set to a multiplier 6.