FOUR SHIELD CARS WERE BEING LOADED INTO THE MINE, ONE ELECTRICAL FUSE BLOWN TO THE ELECTRIC MOTOR, WHEN THIS OCCURRED THE ELECTRIC BRAKE WAS INOPERATIVE THEREFORE THE MANUAL BRAKE CAME INTO PL AY. THE CARS STARTED TO GO FASTER DOWN THE SLOPEAND STRUCK A MOTOR PARKED AT THE BOTTOM AND DERAILED THE BRAKECAR. THE HOIST OPR DID GET THE TRIP SLOWED DOWN TO PREVENT DAMAGE.