| 摘要 |
An apparatus for coupling an induction generator to ac power mains comprises semiconductor switching elements for connecting the induction generator to the ac power mains, a firing circuit for providing firing pulses to the semiconductor switching elements and an enabling means which provides an enabling signal to the firing circuit preferably at a predetermined rotational speed of the shaft of the induction generator below the synchronous speed. The firing circuit comprises means for forming a single firing pulse for each semiconductor switching element for each half cycle of the mains voltage, wherein the duration of each firing pulse increases from a phase angle of 180 DEG of the corresponding phase voltage to a predetermined smaller phase angle of this phase voltage. Further an adjusting element is provided for setting the predetermined smaller phase angle where each firing pulse starts, and a current detection circuit is provided for comparing the firing pulse duration with the period during which a current flows through the corresponding semiconductor switching element. Said means includes a compensating circuit for increasing the firing pulse duration to half the cycle time of the mains voltage. |
