| 摘要 |
PURPOSE:To protect a main motor against excessive fault current by arranging a diode for blocking counterflow to an armature coil, upon grounding of the armature winding, between the armature winding and an armature chopper circuit. CONSTITUTION:Upon occurrence of ground fault X on an armature winding 7A1, fault current induced by the counter electromotive force produced during turn OFF interval of a control commutator element THD flows to the ground side thence flows reversely through the voltage withstanding protective diode PD in an armature chopper circuit 10A to the armature windings 7A1, 7A2. The counterflow is blocked by an anti-counterflow diode ISD arranged between the armature chopper circuit 10A and the armature winding 7A2 and the excessive fault current does not flow through the armature windings 7A1, 7A2. Consequently, the armature windings 7A1, 7A2 in a shunt motor are not heated abnormally with the fault current. |
