Submersible motor

A submersible motor is an asynchronous squirrel-cage motor wetted on the outside and inside, i.e. it is completely immersed in the fluid handled and filled with liquid. It is used as a drive for usually vertical, multistage pumps in boreholes, shafts, wells, containers or open waters, and, unlike the air-filled submerged motor (see Submersible motor pump) is suitable for immersion depths of up to several kilometres (see Submersible borehole pump). See Fig. 1 Submersible motor

The slim design necessary for its use in boreholes substantially reduces the power loss of the rotors in the liquid (see Disc friction), which in rotating cylinders increases by the fifth power of the diameter.

The liquid in the motor lubricates the plain bearings of the rotors. The stator windings must be insulated by fluid-resistant plastics (wet winding) if they are not protected by a can (see Canned motor pump). 

The heat produced by the submersible motor is dissipated into the surrounding fluid handled.

Submersible motors have a power range of up to 3500 kW, with operating voltages up to 10 kV for large motors.