| 摘要 |
PURPOSE:To prevent a DC motor from running away by lowering the detecting level of a current command signal for the prescribed period after a power source is energized, thereby rapidly stopping it when a speed signal is zero and the power source is energized. CONSTITUTION:A comparator 2 detects the difference between a speed command signal e1 and a speed signal e2, and a comparator 4 supplies the difference between a current command signal ei1 and a current signal ei2 to a DC motor drive circuit 6. A comparator 10 sets an output signal to a low level when the signal ei1 becomes the prescribed value or higher. A comparator 12 sets the output signal to a low level when the absolute value of the speed feedback signal is the prescribed value or lower. A malfunction discriminator 13 outputs a malfunction signal when the outputs of the comparators 10, 12 are low level. The detection level of the comparator 10 is lowered for the prescribed period after the power source is energized. In this manner, when the speed feedback signal becomes abnormal and not fed back, a control power source can be rapidly interrupted. |
