Issue with excessive sparking of a DC electric motor

Due to excessive sparking of the electric main drive motor, workers switched to a diesel auxiliary drive. After operating for a period of time the auxiliary drive began to overheat. Staff then switched to a diesel evacuation drive. The evacuation drive was not capable of running at its design speed. After a period of time, the auxiliary drive cooled down enough to allow staff to switch back to the auxiliary drive and complete the evacuation of the passengers. It took 50 minutes from the point at which the auxiliary initially overheated to when all remaining passengers were removed from the ropeway.