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Self-controlled polyphase synchronous motor drive system

  • US 4,364,004 A
  • Filed: 01/29/1980
  • Issued: 12/14/1982
  • Est. Priority Date: 01/29/1980
  • Status: Expired due to Term
First Claim
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1. A self-controlled polyphase synchronous motor drive system for a synchronous motor having a rotor and a polyphase stator, said stator being adapted to have a polyphase voltage applied thereto, said motor drive system comprisingmeans for producing rotor digital timing signals which are equal in number to two times the number of phases of the polyphase stator and representative of the position of the rotor relative to the stator;

  • means for producing pulse width modulation control signals wherein the pulse width thereof is responsive to a motor power factor command signal;

    a plurality of phase control means equal in number to the number of phases of the polyphase stator and responsive to the pulse width modulation control signals, each of said phase control means having a selected two of the stator voltages applied as an input thereto and including means for producing a modulated analog reference signal from one of the two selected stator voltages and means for summing the amplitude modulated analog reference signal with an unmodulated analog reference signal produced from the other of the two selected stator voltages and for comparing the sum thereof with a threshold voltage signal to produce as an output therefrom two digital gating timing signals for each phase of the polyphase stator, each of said phase control means being responsive to the speed of a said synchronous motor such that an absence of digital gating timing signals occurs at zero motor speed and digital timing signals having distortion induced therein by changes of current acting on the inductance of the synchronous motor is produced at low motor speeds, said distortion being large compared to the stator voltage at low motor speeds and as the speed of the synchronous motor increases, the stator voltage increases in magnitude such that said distortion becomes smaller in magnitude relative to that of the stator voltage until the stator voltage level reaches a magnitude wherein the sum of the amplitude modulated analog reference signal and unmodulated analog reference signal exceeds the threshold level to produce digital timing signals substantially free of distortion;

    a digital gating command signal generating means responsive to the digital gating timing signals from each of the phase control means and to the rotor digital timing signals for producing digital gating command signals wherein at zero motor speed and low motor speeds said digital gating command signal generating means is responsive to said rotor digital timing signals to have the leading edge of the digital gating command signals established by the leading edge of a selected one of the rotor digital timing signals until the motor speed reaches a speed wherein digital gating timing signals substantially free of distortion are produced by the phase control means whereupon the leading edge of the digital gating command signals is determined by one of the leading edges of one of the digital gating timing signals from the phase control means and the leading edge of a selected one of the rotor digital timing signals, whichever occurs first in time, and the width of the digital gating command signals is determined by the phase displacement of successive phases which is equal to 360 degrees divided by the number of phases of the polyphase stator, said digital gating command signals being applied to solid state controlled devices to control the current applied to the stator of the controlled synchronous motor.

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