| 摘要 |
PURPOSE:To enable a motor to be picked out exactly and smoothly even if it is rotated at a low speed without residual voltage, by applying standby excitation voltage several times at given time intervals, when there is no residual voltage on the motor. CONSTITUTION:When it is detected that there is no residual voltage, then commercial power frequency is applied to the frequency data of a PWM generation circuit, and an inverter 21 is set to be of maximum output frequency, and the output of a PWM-phase-control-angle-arithmetic section 32d is slowly increased and is applied to a motor 24. When this operation is repeated several times and the residual voltage of the motor 24 comes to 1/2 of excitation voltage, then the rotational frequency of the motor 24 is measured. Arithmetic operations are executed on the rotational frequency to set the frequency data of the PWM generation circuit, and the voltage data of the arithmetic section 32d of PWM are slowly increased up to a voltage corresponding to voltage/frequency hold value, and the motor is picked out. |
