Permanent magnet excited electric motor

  • US 4,998,032 A
  • Filed: 07/13/1988
  • Issued: 03/05/1991
  • Est. Priority Date: 01/13/1986
  • Status: Expired due to Term
First Claim
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1. A brushless dc motor excited by permanent magnets comprisinga laminated stator core having radially extending slots with slot orifices at a coaxial surface of the core, the coaxial surface being cylindrical;

  • at least one winding forming electromagnetic poles defined in the sectors between the slots;

    a plurality of radially thin, annular permanent magnets arranged in alternating polarities in the general form of a ring with a gap circumferentially separating each polarity and formed to rotate with respect to the stator, each magnet forming a rotor pole of a relatively high induction, the faces of the electromagnetic poles facing the faces of the permanent magnets and being separated by a generally cylindrical air gap defined therebetween;

    a plurality of raised portions on each of the stator pole coaxial surfaces extending radially into the air gap, the circumferential width of the raised portions being small compared to the stator pole pitch such that the stator pole pitch is many times the circumferential width of the raised portions; and

    one of the raised portions on each of the stator faces being located around the circumference of the stator core 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 said one raised portion on the stator pole adjacent the given pair is equal to n times the rotor pole pitch, n being a whole number.

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