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Collector-less D-C motor

  • US 3,873,897 A
  • Filed: 05/23/1973
  • Issued: 03/25/1975
  • Est. Priority Date: 05/25/1972
  • Status: Expired due to Term
First Claim
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1. Brushless d-c motor having a permanent magnet rotor (11);

  • a stator (13, 14,

         15);

    a winding (18,

         19) on the stator to generate an electromagnetic field when energized; and

    an air gap (26, 27, 111, 112, 116-119) separating the rotor and the stator;

    controlled semiconductor switching means (38,

         39) controlling pulsed current flow through the winding;

    wherein the width of said air gap is non-uniform, in zones, so that the reluctance of the magnetic circuit which includes said stator, said air gap and said rotor varies with angular position over the circumference of the stator, said zones, in the direction of rotation of the motor being defined by;

    a zone of increasing width of the air gap and hence increasing reluctance of the magnetic circuit extending over a first angular range ( Alpha ) to a maximum (d2), and then a zone of decreasing width of the air gap and hence decreasing reluctance of the magnetic circuit extending over a second angular range ( Beta ) to a minimum (d1), and means (25) synchronizing pulsed energization of the semiconductor switching means and hence of the winding with the angular position of the rotor to generate, electrodynamically, an interrupted, pulsed electromagnetic torque during such pulsed energization of the winding by interaction of the magnet of the rotor with the electromagnetic field, due to energization of the winding and to store during such pulsed energization of the winding a portion of said generating torque in form of magnetic reluctance torque by interaction of the magnet of the rotor with the magnetic structure of the stator when the magnet of the rotor is in an angular range which includes at least part of said zone of increasing width of the air gap, the reluctance torque stored in magnetic form being released to the rotor, during pulse gaps, or interruptions in the generated electromagnetic field, by interaction of the magnet of the rotor with the magnetic structure of the stator when the magnet of the rotor is in an angular range which includes at least part of said zone of decreasing width of the air gap, the alternating component of the electrodynamically generated torque and the magnetic reluctance torque being in phase opposition and, together, providing a net driving torque to the rotor upon its rotation with respect to the stator.

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