| 摘要 |
PURPOSE:To accurately control the speed of an induction motor without using a speed detector nor a voltage detecting converter by controlling a slip frequency having a proportional relation to the torque of the motor. CONSTITUTION:A current component detector 7 inputs a primary current signal and the sinusoidal output signal of a 2-phase oscillator 10 to obtain an exciting current component and a torque current component. A slip frequency calculator 8 calculates from the exciting current component and the torque current component to obtain a slip frequency calculation signal proportional to the slip frequency. A speed detecting subtractor 19 subtracts the slip frequency calculation signal from a frequency command signal to obtain a rotational frequency (assumed signal to the rotational speed). A speed deviation amplifier 20 amplifies a deviation between a speed command signal and a speed presumption signal. A frequency instructing circuit 21 varies a frequency command signal in response to a deviation between the slip frequency command signal and the slip frequency calculation signal. |
