| 摘要 |
PURPOSE:To stop a VVVF due to a commutation failure by always accurately calculating the lowest current necessary for a normal reactance and commutation, and limiting the upper limit frequency of the operation. CONSTITUTION:A commutation reactance calculator 12 inputs the output of a current detector 2 and the output of a commutation capacitor/charging voltage detector 13, and calculates the accurate commutation reactance of the present operating state. A commutation current setter 10 inputs the induced voltage of a motor 16 from a capacitor charging voltage detector 12, the commutation reactance value from the calculator 12 and the output from the oscillator 11 and calculates the minimum current necessary for the commutation. A speed reference limiter 8 operates to reduce a speed reference only when the minimum current necessary for the commutation of the output of the setter 10 is larger than the secondary current of a power source transformer 1 of the output of the detector 2. |
