Importance

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Abstract

A variable speed variable torque brushless DC motor (32) having at least one position sensor (34) with each position sensor producing a position signal indicating position of the rotor and having a frequency equal to a frequency of excitation current applied for activating stator windings in accordance with the invention includes a pulse generator (36) for producing first pulses having a frequency which is equal to nf where n is the number of position sensors and f is the frequency of excitation current; a source (39) of a first signal having a frequency f1 wherein f1.gtoreq.f; a source (41) of a variable frequency second signal having a frequency f2 with f2.gtoreq.f1; an excitation circuit (48) for applying excitation current pulses to the stator windings with the excitation current pulses occurring in response to position signals produced by the at least one position sensor; a delay circuit (38, 40, 42, 44 and 46) responsive to the first pulses, the first signal and the second signal for delaying the application of the position signals to the excitation circuit the delay being equal to mf1/nf2 with m being an integer.

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First Claim