Rotron, Inc.

Alan F Grouse

Fred A Brown

A simplified fan and brushless DC motor has a rotor with an annular permanent magnet that is magnetized in segments about its circumference and is associated with a wave-wound stator coil. Alternate circumferential segments of the magnet are oppositely polarized. Fan blades are located within the annular magnet. The wave-winding varies in position to present alternate magnetic fields opposite in direction to the rotor magnet outer surface to cause rotation thereof. The stator is ironless. The coil can have two bifilar windings alternately energized. A Hall device is, typically, employed for commutation along with suitable switching circuitry.

Ironless, brushless DC motor with wave-winding

A simplified fan and brushless DC motor employs an annular permanent magnet magnetized in segments about its circumference. Each segment is oppositely radially magnetized with respect to its adjacent segments. Fan blades are located within the annular magnet. A coil comprising two electrically independent and bifilar wound windings, connected to be oppositely energized, and an electromagnet structure defining two pole pieces reside outside the permanent magnet annulus. A Hall effect device alternately energizes the separate coil windings in response to passage of the segments of the rotor magnet to alternately produce opposite magnetic fields in the pole pieces. Thus commutated, the double coil arrangement affects rotation of the rotor and the fan blades.

Simple brushless DC fan motor with reversing field

An arrangement for sensing the operating condition of an alternating current machine employs a Hall switch on the stator which is subjected to the alternating magnetic field established during operation. The Hall switch has a magnetic field strength threshhold below which it will not be actuated. During normal operation of the machine, the alternating field strength will cyclically exceed the switch threshhold, thereby generating a series of pulses at the frequency of alternation of the field. Should the field strength decrease as a result of overload of the machine, a decrease in line voltage, or the like, to a level below the threshhold level of the switch, the pulse output of the switch will cease. Circuitry responsive to the absence of periodic pulses actuates an indicator circuit to warn of the faulty operation.

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Woodstock, NY, United States of America

Alan F Grouse