| 摘要 |
PURPOSE:To prevent thyristor trips by providing a means for comparing a power- supply voltage and a motor induced voltage and making it possible to switch from motor operation to regenerative operation only in the case the power-supply voltage is larger than the induced voltage. CONSTITUTION:A speed-feedback signal VSB which is detected by a rotary generator 6 is compared with a speed-command signal VSP, and a current-command signal VCP is obtained. The current-command signal VCP and a current-feedback signal VCB are input to an operation identifying circuit 8, and a pulse-phase shifter 3 is controlled, thereby a motor 5 is regeneratively operated reversibly. In the operation identifying circuit 8, is provided a voltage identifying circuit 9 wherein the average value VS of the power-supply voltages and the absolute value VM of the motor induced voltage are input and compared. When VS<VM, switching of signals F and R to be given to the pulse-phase shifter 3 is blocked. Since the switching to the regenerative operation is made only under the conditions the overcurrent is not generated in the thyristors, the thyristor trips can be prevented without fail. |
