| 摘要 |
PURPOSE:To shorten the synchronization acquisition time by inputting as a preliminary signal the output frequency signal of a variable voltage variable frequency power source and a rotary signal of an AC motor to a phase synchronizing loop circuit. CONSTITUTION:A phase comparator 9 applies the voltage proportional to the phase difference between the terminal voltage VM of a synchronous motor and the output AC signal VC of a voltage controlled oscillator 11 to a low pass filter 10. A switch unit 12 inputs as the input F3 of a voltage controlled oscillator 11 the output F1 of a low pass filter 10 when the phase synchronization loop is in synchronized state, the signal corresponding to the output frequency of variable voltage variable frequency power source when in asynchronous state or the preliminary signal F2 corresponding to the rotating speed of the AC motor. In this manner, the synchronization acquisition time of the phase synchronizing loop can be shortened. |
