| 摘要 |
PURPOSE:To prevent an overvoltage and an overcurrent from occurring when a current collector passes a section by detecting the current collecting state of the collector, and gradually reducing a control current flow rate in response to the variation in the detected value. CONSTITUTION:A comparator 16 outputs a signal when the variation Ecf of a filter capacitor voltage Ecf comes to a reference value or higher. A main motor current reducing circuit 2 outputs a pulse to gradually reduce a main motor current IM to the gate of a chopper. When a time T4 is elapsed,a timer 21 is operated to open a gate circuit. When time T4+T5 is elapsed after the comparator 16 outputs a signal, a timer 22 is operated to restart a chopper. Thus, it can prevent an overvoltage and an overcurrent from occurring when a current collector passes a section. |
