| 摘要 |
<p>PURPOSE:To smoothly switch to an air brake at the regeneration failure time by invalidating the detection of a power source voltage at the regeneration failure time and switching to a generating brake with an overvoltage suppressing resistor as a load resistor for the prescribed time. CONSTITUTION:When the fact that the voltage Ecf of a filter capacitor 5 is a reference value or higher is detected by a comparator 31 at the regeneration brake time, an ON command is outputted from a firing circuit 33 to an overvoltage suppressing thyristor 13. Simultaneously, a main motor current IM is reduced by a reducing circuit 34 of a chopper 10. Further, it is instructed not to detect the voltage Ecf by a voltage no detection instructing circuit 36. On the other hand, a breaker 3 is opened by delaying for the prescribed time by a time element 35. A generating brake circuit is composed with an overvoltage suppressing resistor 12 as a load while reducing the current IM during this prescribed time, thereby smoothing switching to an air brake.</p> |
