Method and apparatus for controlling induction motors

Electricity: motive power systems – Induction motor systems – Primary circuit control

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318807, H02P 700

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active

055414885

ABSTRACT:
The present invention provides for detecting rotor speed through the use of sense coils on the stator teeth. Voltage ripples caused by the rotor slots is detected by combining the signals of several such sense coils so that the fundamental voltage signal is cancelled or rejected and only the ripple voltages remain, a signal proportional to rotor speed. Several alternative methods for implementing that technique are discussed herein. At low induction motor speeds, the present invention filters out the voltage ripples and incident third harmonics and instead estimates rotor speed from the fundamental voltage. When the induction motor is already being driven by a prime mover, the present invention selects a proper initial frequency command for initial motor start by identifying rotor speed from the PWM inverter. Further, the present invention provides for using a generator to control voltage to the induction motor, with a PWM inverter to control frequency signals to the induction motor.

REFERENCES:
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Article entitled: "A Novel Position Sensor Elimination Technique for the Interior Permanent-Magnet Synchronous Motor Drive" written by Ashok B. Kulkarni and Mehrdad Ehsani, printed in IEEE Transactions On Industry Applications, vol. 28, No. 1 Jan./Feb. 1992.
Article entitled: "Vector Control of Induction Motor Without Shaft Encoder" by Tsugutoshi Ohtani, Noriyuka Takada, and Koji Tanaka and published in IEEE Transactions On Industry Applications, vol. 28, No. 1, Jan./Feb. 1992.
Article entitled: "Brushless dc Motor Control without Position and Seed Sensors" written by Nobuyuki Matsui and Masakane Shigyo, published in IEEE Transactions On Industry Applications, vol. 28, No. 1, Jan./Feb. 1992.
Article entitled: "Implementation of Direct Stator Flux Orientation Control on a Versatile DSP Based System" written by Xingyi Xu and Donald W. Novotny published in IEEE Transactions On Industry Applications, vol. 27, No. 4, Jul./Aug. 1991.
Article entitled: "Rotor Position Detection Techniques for Brushless Permanent-Magnet and Reluctance Motor Drives" written by P. W. Lee and C. Pollock, University of Warwick, Coventry CV4 7AL, United Kingdom.

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