| 摘要 |
PURPOSE:To switch shocklessly a motor when switching to an inverter operation by a commercial power source by reducing an inverter frequency command by a level corresponding to the decrease in the rotating speed of the motor. CONSTITUTION:A multiplier 40 input a fvrequency correction signal DELTAVfm, and outputs a voltage signal V having a magnitude obtained by multiplying the value of the signal DELTAVfm by a constant. The signal V is added by an adder 42 through an analog switch 41 to the signal DELTAVfm, and the sum is supplied as an inverter frequency command to an oscillator 28. The switch 41 is closed by a lock detection signal of a lock detector 33. Thus, an inverter frequency command is corrected by the signal V siumultaneously upon reapplying of the voltage to decrease stepwisely. Accordingly, an increase in a slip until a torque is established is suppressed, and since the inverter output current is accordingly reduced, an overcurrent trip is prevented. |
