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Multi-phase brushless motor with increased starting torque and reduced torque ripple

  • US 4,912,379 A
  • Filed: 05/19/1988
  • Issued: 03/27/1990
  • Est. Priority Date: 05/21/1987
  • Status: Expired due to Term
First Claim
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1. A more-than-four phase brushless motor including a stator having a plurality of drive coils each corresponding to a specific phase of said motor and a rotor having a plurality of field magnet poles of successively alternating polarity, comprising:

  • position detecting means consisting of two Hall generators magnetically coupled to the field magnet poles for detecting the positions of said rotor and generating position signals corresponding to the positions thereof;

    speed detecting means for detecting the rotational speed of said rotor and generating a signal corresponding to the detected speed thereof;

    drive circuit means for supplying drive currents to said drive coils of said stator so as to generate torques for rotation of said rotor;

    first processing circuit means responsive to the position signals from said position detecting means for outputting first exciting signals to said drive circuit means so that in response to the first exciting signals said drive circuit means supplies the drive currents to said drive coils thereof;

    second processing circuit means responsive to the speed signal from said speed detecting means and one of said position signals from said position detecting means for outputting second exciting signals to said drive circuit means so that in response to the second exciting signals said drive circuit means supplies the drive currents thereof;

    startup detecting means for detecting the driving condition of said motor and generating a signal indicative of the driving condition; and

    switching circuit means coupled to said first and second processing circuit means for performing a switching operation between said first and second processing circuit means in response to the condition-indicative signal from said startup detecting means so that said first processing circuit means outputs the first exciting signals to said drive circuit means at startup of said motor and said second processing circuit means outputs the second exciting signals thereto after the startup.

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