| 摘要 |
PURPOSE:To always effectively set synchronization of an induction motor by accurately predicting the synchronizing timing from the frequency of the induced voltage of an induction motor. CONSTITUTION:After a power source is instantaneously interrupted, a controller 4 is reset, and the main switching element of a main circuit 1 remains OFF. When the power source is recovered and a phase signal P is input, a frequency measuring circuit 5 starts predicting the frequency. The controller 4 accurately measures the period J continuously by the measuring circuit 5, thereby calculating so as to generate a correction signal C when the predicted calculation of the frequency is obtained. Thus, the signal (e) of the frequency in response to the rotating speed signal (d) and the rotating speed signal (d) are corrected by the signal C, a control signal (g) corresponding to the output of the frequency is generated, and supplied to the main circuit 1. |
