METHOD AND SYSTEM FOR CONTROLLING AN ELECTRIC MOTOR WITH VARIABLE SWITCHING FREQUENCY AT VARIABLE OPERATING SPEEDS

摘要

A data processor establishes a first range of rotational speeds of a rotor of the motor from a first lower limit to a first higher limit and a second range of rotational speeds from a second lower limit to a second higher limit. A hysteresis band or a rotational range of speeds is established such that during operation in the first range the first higher limit is adjusted (e.g.· raised by a first amount to be greater than the second lower limit). A sensor detects or measures a rotational speed of a rotor of the motor. The data processor determines whether the measured rotational speed falls within the first range or the second range, as adjusted by the hysteresis band, to identify a selected speed range. A switching frequency of a pulse-width modulation signal is varied in accordance with the selected speed range.