Patent ID: 6700297
Filing Date: 2004-03-02
Classification: H02K

Abstract:
A brushless electric machine having a stator and a rotor spaced from the stator to define a main air gap, the stator producing a first flux in the rotor and the main air gap, the machine further comprising:a rotor having an axis of rotation and having a plurality of rotor poles disposed at least partly around the axis of rotation and facing the main air gap, the plurality of rotor poles being spaced apart and having PM material disposed in the spaces between said rotor poles for blocking conduction of a second flux between said two rotor poles when excited by a direct current of one polarity; at least one stationary excitation coil that is separated from the rotor by a secondary air gap, for conducting direct current so as to induce the second flux in the rotor poles across the secondary air gap, said flux being conducted through the rotor to reach the main air gap; and a stationary cryogenic cooling enclosure for containing the stationary excitation coil and for cooling the stationary excitation coil, such that the stationary excitation coil is operated in a superconducting state.