Patent ID: 8807970

Claim:
A multistage electric motor for a submersible pump, the motor comprising: a casing defining a substantially cylindrical containment structure such that a fluid being conveyed by the pump passes along the outside of the casing; a plurality of motor stages connected in series within the casing, each motor stage comprising a stator with at least one winding and at least one bearing each of which is susceptible to excessive temperatures generated in the motor and wherein each stator is separated from the stator in the next stage by a coupling which allows connection between the adjacent stators; a cooling fluid path forming a continuous recirculating loop within the stator of each stage that is independent of the cooling fluid paths of the other of the plurality of stages, each cooling fluid path comprising an inner channel, further comprising a plurality of channels spaced around the inner circumference of the stator, and an outer channel, further comprising a plurality of channels spaced around the outer circumference of the stator, such that a cooling fluid passes through the inner channel to remove heat from the at least one winding and the at least one bearing and then passes through the outer channel that is adjacent the casing to establish heat exchange communication with the fluid being conveyed in order to reduce temperature differences between each stator within the multistage motor.