Patent ID: 7508157

Claim:
A motor system for converting electrical energy from line power into rotational mechanical energy comprising: an air core motor including a rotor with permanent magnet poles and a stationary armature with air core windings located within a magnetic airgap defined on one side by said permanent magnetic poles; said permanent magnet poles are set to produce a level of magnetic flux density through said air core windings in said magnetic airgap such that a back emf is produced in said windings that is comparable to the voltage of said line power when the rotation of said permanent magnet poles across said air core windings is synchronous with said line power; an electronic variable speed drive that couples to said windings and accelerates said rotor to near line synchronous speed by ramping up the frequency of power to said air core windings; a detector that recognizes when said motor rotor approaches near line synchronous speed and produces a signal to indicate that said motor rotor has reached near line synchronous speed; a switch responsive to said signal that couples said air core windings to said line power when the frequency of said back emf approaches the frequency of said line power.