Patent ID: 8076809

Claim:
A submersible electric motor for down hole use well, the motor comprising: a shaft; a plurality of rotors and bearings mounted on said shaft, each rotor comprising a hollow cylinder comprising a stack of laminations, a copper bar and end rings, and wherein each rotor is supported by at least one bearing; a stator positioned external to said rotors; a running clearance located between an internal diameter of the stator and an outside diameter of the rotor; and wherein the motor is filled with an oil; wherein the oil comprises a base oil comprising a hydrocarbon and a plurality of nanoparticles suspended in said base oil, wherein the nanoparticles include a functional group appended thereto, wherein the functional group is selected from alkyl, alkenyl, aromatic hydrocarbons, or mixtures or derivatives of these groups, or polymers of such; and wherein the oil comprises up to about 30% by volume nanoparticles.