| 摘要 |
PURPOSE:To make a soft start and a current control loop unaffected by positive feedback, by providing a filter circuit and a clamping circuit in the front portion of the current control loop, and obtaining a directional signal from within the current control loop. CONSTITUTION:A current base signal from a speed control circuit 2 is input to a current control circuit 5 through the filter circuit 8 by means of a driving circuit having a thyristor conversion circuit. To this filter circuit 8., for instance, a clamping circuit which consists of 2 pieces of diodes connected in parallel in a reverse direction and FFT is connected, and the current base value is blocked in such a manner that the value is sufficiently low so as not to lose directivity during a period of gate lock. Further the input signal to a directional signal circuit 7 is to be obtained from within the current control circuit 5. On doing this, a soft start is possible when changing over a thyristor conversion circuit, and the positive feedback is made not to affect the current control loop. |
