Temperature compensated magnetic bearing system for a watthour meter

An induction watthour meter including a stator, a rotor and a temperature compensated magnetic bearing system for supporting said rotor for rotation about a vertical axis, wherein said bearing system comprises:

• upper and lower magnet mounting members carried by said rotor and said stator, respectively;
• upper and lower substantially identical hollow cylindrical permanent magnets having identical and mutually opposite annular pole face ends and carried by said upper and lower magnet mounting members, respectively, in concentric alignment such that the magnetic fluxes of the opposing pole face ends are mutually interacting to support said rotor by maintaining said upper permanent magnet at a predetermined support gap spacing above said lower permanent magnet, and further such that identical substantially non-magnetic flux return paths extend from radially outward portions of the pole face magnetic fluxes of said permanent magnets and along the outer diameters thereof;
• and
• upper and lower substantially identical temperature compensating sleeves having identical and mutually opposite cylindrical ends extending from adjacent the opposing pole face ends of said upper and lower permanent magnets, respectively, and along the inner magnet diameters in a cylindrical body terminating at the opposite pole face ends of each of said permanent magnets, said temperature compensating sleeves having a magnetic temperature coefficient characteristic opposite from the magnetic temperature coefficient characteristic of said permanent magnets such that said compensating sleeves define identical shunt flux return paths for radially inward portions of the pole face magnetic fluxes of said permanent magnets with said shunt flux return paths varying inversely with the magnetic characteristics of said permanent magnets to maintain substantially low variations in said support gap spacing with changes in temperature.