Patent ID: 7129611

Claim:
A brushless electric machine comprising: a stator and a rotor spaced from the stator to define a radial air gap relative to an axis of rotation for the rotor; a rotor having an axis of rotation and having pairs of rotor pole portions of opposite polarity disposed at least partly around a circumference of the rotor and having axially projecting extensions projecting from at least one end of the rotor toward a secondary air gap; at least one stationary excitation coil assembly for receiving direct current from an external source and being positioned across the secondary air gap so as to induce a component of flux in the rotor pole portions which increases a resultant flux in the radial air gap when said direct current is of a first polarity and which reduces resultant flux in the radial air gap when said direct current is of a second polarity opposite said first polarity; and wherein permanent magnet (PM) material is disposed between the rotor pole portions and is also disposed between rotor pole portions of one polarity and a core portion of the rotor for containing the component of flux in the rotor pole portions as the component of flux is conveyed to the radial air gap and for inhibiting the component of flux from leaking from said pole portions prior to reaching the radial air gap when said direct current is of the first polarity; further comprising pole extensions extending from said at least one end of the rotor and an end ring attached to said pole extensions to provide a magnetic path to the secondary air gap, and said end rings have pole pieces corresponding to said pole extensions; and wherein said pole pieces have stepped flanges for connecting to the pole extensions and wherein the flanges are made of a plurality of stacked laminations.