Current decay control in switched reluctance motor

  • US RE36,568 E
  • Filed: 08/26/1997
  • Issued: 02/15/2000
  • Est. Priority Date: 12/29/1993
  • Status: Expired due to Term
First Claim
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1. A circuit for controlling residual current decay in a single or polyphase SRM comprising:

  • sensing means for sensing the position of a rotor of the motor;

    switch means for directing current flow into a phase winding of the motor when the phase is active and for recovering or dissipating energy in the winding when the phase is inactive, the switch means comprising a first set of switches and a second set of switches, said sets of switches being on respective sides of the phase winding with one set of switches being activated when the phase is active, and deactivated when the phase is inactive;

    signal generating means providing an operating signal to the switch means to control current flow and recovery or dissipation, the signal generating means including a PWM signal generator whose output signal pulse width and frequency are a function of the SRM'"'"'s operating characteristics, the second set of switches being modulated by operating signals from the signal generating means whereby operation of the second set of switches is controlled as a function of the signal characteristics of the operating signal;

    a capacitor connected in series with the phase winding and charged by the current in the phase winding when the phase becomes inactive thereby to recover a portion of the energy; and

    control means responsive to the sensing means for controlling the signal generating means for the signal generating means to provide operating signals having operating characteristics which differ when a phase is active and when it is not, thereby to facilitate energy recovery or dissipation when the phase becomes inactive, the control means effecting both frequency and/or duty cycle of the operating signals to control the rate of decay of the current and consequently motor noise, the control means being responsive to inputs from the sensing means when the phase becomes inactive to reverse the pulse width of the PWM operating signals produced by the signal generating means from those which are produced when the phase is active.

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