Permanent magnet excited electric motor

  • US RE35,763 E
  • Filed: 07/23/1996
  • Issued: 04/07/1998
  • Est. Priority Date: 01/13/1986
  • Status: Expired due to Term
First Claim
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1. A brushless dc motor having a cylindrical type air gap, a slotted stator core and permanent magnet excitation, the air gap being defined between circumferentially facing faces of the slotted stator core and an opposing ring of permanent magnets formed to rotate with respect to the core, the core having a plurality of radially extending winding slots, and the motor including at least one winding forming electromagnetic poles defined in the sectors between slots of the stator core with a plurality of raised portions on each of the electromagnetic pole faces extending radially into the air gap, the circumferential width of the raised portions being small compared to the circumferential width of the pole pitch, the raised portions on each of the pole faces being located such that the distance measured in the direction of rotor rotation from the center of a stator slot defined between any given pair of stator poles to the center of one of said raised portions on the stator face adjacent said given pair of stator poles is equal to n times the rotor pole pitch, n being a whole number.

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