| 摘要 |
<p>PURPOSE:To prevent a cam switch from fusion-damaging at grounding defect around a DC motor by connecting a starting resistor from the motor to a ground potential side. CONSTITUTION:A pantograph 1 for collecting a current from a trolley wire W, a line breaker 2, a DC motor 3 and a starting resistor 4 are connected in series. The one side terminal 4a of the resistor 4 to which the motor 3 is not connected is grounded. A defect current flows to the ground when a grounding defect occurs around the motor 3, but since the resistor 4 is connected from the motor 3 to the ground potential side, the current flows from the power source side of the resistor 4, i.e., the other side terminal 4b side to the ground. Accordingly, cam switches 5a-5c can be protected against a damage due to the grounding defect around the motor 3.</p> |
