| 摘要 |
<p>PURPOSE:To prevent occurrence of failures by opening a chopper-shorting means when a main-circuit current exceeds a preset value in the case a motor is controlled, by shorting a chopper and applying a full voltage to the motor. CONSTITUTION:When an advance or backing switch MF or MR is switched, and the conduction rate of a chopper 3 is controlled by applying an accelerator pedal, a charging current is flown into a capacitor C1. When the charging current exceeds the Zener voltage value of a Zener diode ZD2, the gate of a thyristor S1 is opened, and a relay coil 4 is energized. Therefore, the chopper 3 is shorted by a switch 4a. When a load current has increased, and the voltage sensed by a sensing resistor R1 exceeds the preset value of a comparator 8, a thyristor S2 is turned on by the output signal of the comparator 8, the thyristor S1 becomes non-conductive, and the contact 4a is forcibly dropped out, thereby the chopper operation is commenced.</p> |
