Method and device for controlling a brushless electric motor
First Claim
1. A method for controlling a brushless electric motor having switching means for selectively supplying current to armature windings of the motor from a DC-power supply, the method comprising the steps ofmeasuring back-electromotive forces developed during operation in the windings of the motor, generating a low reference voltage and a high reference voltage, comparing said back-electromotive forces with said low and high reference voltages for generating commutation signals each time a measured back-electromotive force with positive slope crosses the high reference voltage, and/or a measured back-electromotive force with negative slope crosses the low reference voltage, and using said commutation signals to commutate the switching means.
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Abstract
The brushless electric motor (M) is provided with switching means (Q1-Q6) for selectively supplying current to the armature windings (U, V, W) of the motor (M) from a DC-power supply (1) The switching means (Q1-Q6) are controlled by measuring the back-electromotive forces developed in the windings (U, V, W) during operation and comparing these measurements with a high and low reference voltage, in such a way that each time a measured back-electromotive force with positive slope crosses the high reference voltage or a measured back-electromotive force with negative slope crosses the low reference voltage, a commutation signal is generated to commutate the switching means (Q1-Q6), this provides a highly simplified control of the switching means.
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Citations
10 Claims
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1. A method for controlling a brushless electric motor having switching means for selectively supplying current to armature windings of the motor from a DC-power supply, the method comprising the steps of
measuring back-electromotive forces developed during operation in the windings of the motor, generating a low reference voltage and a high reference voltage, comparing said back-electromotive forces with said low and high reference voltages for generating commutation signals each time a measured back-electromotive force with positive slope crosses the high reference voltage, and/or a measured back-electromotive force with negative slope crosses the low reference voltage, and using said commutation signals to commutate the switching means.
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6. Device for controlling a brushless electric motor provided with switching means for selectively supplying current to the armature windings of the motor from a DC-power supply, comprising
means for measuring the back-electromotive forces developed during operation in the windings of the motor, means for generating a low and a high reference voltage, and means for comparing said back-electromotive forces with said low and high reference voltages and generating commutation signals each time a measured back-electromotive force with a negative gradient crosses the low reference voltage, or a measured back-electromotive force with a positive gradient crosses the high reference voltage, said commutation signal being supplied to a commutation generator controlling said switching means.
Specification