Brushless D. C. motor and control assembly

An electronically commutated integrated motor and control assembly particularly suitable for use in air moving applications comprising:

• a stator core with at least one winding disposed thereon;
• a permanent magnet rotor adapted to rotate about an axis of rotation in response to rotating magnetic fields in the stator core;
• means for developing a position control signal indicative of the rotational position of said rotor;
• said means for developing a position control signal including a sensor positioned adjacent the rotor for generating a control signal responsive to the rotational position of said rotor;
• means for energizing said at least one winding during a cycle of applied power in a predetermined sequence in response to the position control signal;
• and
• a control circuit for connecting power, through switching means, the control circuit to determine periods of lower rotational torque during the cycle of applied power, to provide power pulses to periodically energize said at least one winding during periods of generation of higher rotational torque, and for inhibiting the supply of power to the at least one winding during the determined periods of lower rotational torque thereby to provide increased operating efficiency.

A method of controlling and operating a brushless DC motor in the form of a single phase motor having winding means in the form of two excitation windings that are sequentially energized during each complete cycle of applied power, said method including:

• determining periods of reduced operating efficiency during each cycle of applied power, supplying power to the winding means primarily only during periods of greater operating efficiency during each cycle of applied power, and inhibiting the application of power to all of the winding means during at least part of that segment of each cycle of applied power when reduced operating efficiency would otherwise result;
• and wherein the method further comprises energizing a first one of the windings at the beginning of the first half of an applied power cycle but not energizing the second one of the windings, and continuing to energize the first one of the windings during a period greater operating efficiency;
• inhibiting energization of the first winding during at least part of the portion of the first half of the applied power cycle associated with reduced operating efficiency and continuing to inhibit energization of the second one of the windings until the end of the first half of the power cycle;
• energizing the second winding at the beginning of the second half of the applied power cycle and continuing to energize the second winding during a period of greater operating efficiency;
• inhibiting energization of the second winding during at least part of the portion of the second half of the applied power cycle associated with reduced operating efficiency;
• and inhibiting energization of the first winding during the second half of the applied power cycle;
• whereby no winding is energized during preselected portions of each applied power cycle.