| 摘要 |
PURPOSE:To bring first and second AC power supplies into synchronous state where fluctuation of frequency is suppressed, without producing DC component, by providing means for detecting phase difference between the first and second AC power supplies and controlling a frequency command circuit so that the phase difference will be zero. CONSTITUTION:A phase limiter means 11 for limiting a differential phase signal detected through a phase difference detecting circuit 7 is provided in order to suppress fluctuation rate of inverter output frequency. Furthermore, a frequency command circuit 9 is provided with a frequency limiter means 12 in order to limit the inverter output frequency within a set value even if a bypass AC power supply fluctuates considerably. A sine wave generating circuit 13 generates a single cycle sine wave pattern comprising symmetrical positive and negative half waves for the frequency signal from the frequency command circuit 9 in order to eliminate DC component in the inverter output voltage. Consequently, AC power supply having fluctuating frequency can be followed up smoothly and stably. |
