Control for high speed operation of brushless permanent magnet motor
First Claim
1. A method for controlling a brushless permanent magnet motor having stator windings connected in a star configuration which provides a stator neutral node and in which windings are induced back EMF fundamental and third harmonic components, and a rotor which rotates relative to the stator windings, the motor being driven by an inverter having electrical nodes, comprising the steps of:
- extracting a first signal in which the third harmonic component is dominant;
filtering the first signal to generate a second signal which substantially contains only the third harmonic component;
integrating the second signal to provide a third signal comprising the time integral of the second signal;
communicating the third signal to a controller which controls operation of the inverter;
at preselected intervals of operation of the motor, deliberately precluding application of current signals to one of the stator windings of the motor, sensing a voltage of the respective stator winding and generating a fourth signal with information about the back EMF experienced by the respective stator winding; and
communicating the fourth signal to the controller.
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Accused Products
Abstract
A method and apparatus for operating a brushless permanent magnetic motor at speeds where zero crossings of stator phase voltages becomes unavailable, wherein applications of stator currents to one stator phase is temporarily halted to allow current in the phase to reach zero, and the zero crossings of the internal motor voltage is detected as a surrogate for the zero crossings of the stator phase back EMF. A controller can react to the detected zero crossings as if the phase current was being applied.
92 Citations
14 Claims
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1. A method for controlling a brushless permanent magnet motor having stator windings connected in a star configuration which provides a stator neutral node and in which windings are induced back EMF fundamental and third harmonic components, and a rotor which rotates relative to the stator windings, the motor being driven by an inverter having electrical nodes, comprising the steps of:
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extracting a first signal in which the third harmonic component is dominant; filtering the first signal to generate a second signal which substantially contains only the third harmonic component; integrating the second signal to provide a third signal comprising the time integral of the second signal; communicating the third signal to a controller which controls operation of the inverter; at preselected intervals of operation of the motor, deliberately precluding application of current signals to one of the stator windings of the motor, sensing a voltage of the respective stator winding and generating a fourth signal with information about the back EMF experienced by the respective stator winding; and communicating the fourth signal to the controller. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A system for controlling a brushless permanent magnet motor having stator windings connected in a star configuration which provides a stator neutral node and in which windings are induced back EMF fundamental and third harmonic components, and a rotor which rotates relative to the stator windings, the motor being driven by an inverter having electrical nodes, comprising:
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means for extracting a first signal in which the third harmonic component is dominant; a filter for filtering the first signal to generate a second signal which substantially contains only the third harmonic component; an integrator unit for integrating the second signal to provide a third signal comprising the time integral of the second signal; a controller to which the third signal is communicated and which controls operation of the inverter, the controller being configured to deliberately preclude application of current signals to one of the stator windings of the motor during preselected intervals of operation of the motor; means for extracting a stator winding voltage of the respective stator winding during the preselected intervals, and to generate a fourth signal with information about the back EMF experienced by the respective stator winding, which fourth signal is communicated to the controller. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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Specification