West hoist motor was deenergized to replace brushes on the motor. Upon reenergizing at 10:20 am, it was found that there was no power to the PLC controls. Mine evacuation began and MSHA notified about 10:35am. It was found that the uninterruptable power supply (UPS) was bad in the control power line. This unit was replaced and the hoist was put back into operation at 10:55 a.m.