| 摘要 |
PURPOSE:To reduce the power loss of a chopper and to avoid the production of an arc by chopping a main transistor in a high duty while an electromagnetic switch is closed. CONSTITUTION:The rotating speed of a motor 2 for driving an electric motor vehicle is controlled by a transistor chopper 3 or a bypass switch 6 having a mechanically opening and closing contact. A control circuit CC varies the duty ratio of the base current of the chopper 3 by the operation of an accelerator pedal P. When the switch 6 is closed, this closure is detected by a shunt resistor R and an amplifier AMP, and a base current is supplied in a duty ratio having an OFF period shorter than the contact moving time when the switch 6 is opened to the chopper 3 during the closing period. Accordingly, even if an arc is generated between arcless or contacts when the switch 6 is opened, the chopper 3 is turned ON in a short time, thereby extinguishing the arc. Therefore, the contact of the switch 6 can be suppressed to the minimum limit. |
