Devices that can change the speed, position or torque of a DC powered controller fall into this category. DC Motors, unlike their AC motor counterparts, can have their leads switched so that the current runs in the opposite direction. Small DC Motors are used in appliances and tools, but this universal motor, when larger, can be used in elevators and electric vehicles.
Physical damage, overheating or corrosion can cause shortages and in some cases, motor failure. Repair can include replacement of parts such as bearings, brushes, or insulation, or the realignment of parts.