Importance

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Abstract

A motor powered by a dc power source has a stator having a single phase winding. A power switching circuit of the motor has power switches for selectively connecting the dc power source to the single phase winding. A permanent magnet rotor in magnetic coupling relation to the stator drives a fan. A position sensor on the stator detects the position of the rotor and provides a position signal indicating the detected position. A control circuit including a microprocessor responsive to the position signal and connected to the power switching circuit selectively commutates the power switches to commutate the single phase winding as a function of the position signal. The microprocessor controlled motor is programmed to reduce operation at speeds at which resonance occurs and provides an alarm in the event that the static pressure of the air driven by the fan is unacceptable. The motor employs a simple, low cost and reliable power switching network and has a start mode during which the rotor is accelerated at a constant rate and a restart mode which is initiated when a locked rotor is detected. The microprocessor may be programmed to provide constant commutation periods in its normal operating mode and has a safe operating area avoiding overtemperature operation without current sensing. The motor employs a simple, low cost, lossless, current limiting power supply drives a fan at multispeed operation or as part of an automatic condenser control.

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First Claim