| 摘要 |
PURPOSE:To ensure the changeover from brake control to drive control by a method wherein, when an opened line-breaker is re-closed for the purpose of changeover from the brake control to power control, a pre-determined field pre-exciting current is applied beforehand and, after the voltage of an armature winding becomes zero or its polarity becomes the polarity of a driving state, the line-breaker is closed. CONSTITUTION:A line-breaker 8 is not closed simultaneously with a circuit breaker 6 but is closed through the operation of a relay PR when a field current output signal I2 exceeds a certain value and a current detector 19 is turned on. In this case, a field pre-exciting current is approximately the same as the minimum value of a control current. When the line-breaker 8 is closed, the voltage of an armature winding 9 becomes zero or its polarity becomes the polarity of a power running state, i.e., the polarity reverse to that of a brake state, and a short-circuit current does not flow through the armature winding 9. |
