How may temporary repairs to an open DC propulsion armature coil be made, allowing continued operation until permanent repairs can be made?

Correct Answer: Option D — disconnecting coil ends, insulating each, and short circuiting the two commutator bars

Emergency repairs for an open armature coil involve disconnecting the affected coil ends, insulating them from ground, and placing a jumper across the corresponding commutator bars. Per IEEE 45, this bypasses the faulted loop, preventing destructive arcing while allowing temporary propulsion operation.