| 摘要 |
<p>PURPOSE:To protect an induction motor against an overcurrent by preventing a controller for an electric rolling stock from starting when the difference between the maximum value and the minimum value of the rotating speed of the motor becomes larger than a predetermined set value. CONSTITUTION:A switch 4a is switched to a minimum value detector 1 side at the time of power drive, and a slip frequency is added by an arithmetic unit 3 to the minimum value FMIN of signals FM1-FMn representing the rotating frequencies of induction motors M1-Mn as an inverter frequency signal FINV. On the other hand, the switch 4a is switched to a maximum value detector 2 side at the time of braking, and the slip frequency is subtracted from the maximum value FMAX by the unit 3. A logic unit 5 subtracts the value FMAX and the minimum value FMIN, and when the difference is larger than a predetermined set value, a signal OFF for preventing an inverter from starting is output.</p> |
