High efficiency electronically commutated motor

Abstract

An electronically commutated electric motor includes a rotor, a stator and an electronic drive. The rotor is journaled to rotate about an axis of rotation, the stator is stationary relative to the rotor, and the electronic drive provides synchronous power to the stator and drives the rotor. The rotor has two ferromagnetic radially spaced apart co-rotating rotor portions having a circumferential array of alternating polarity permanent magnet poles that drive magnetic flux back and forth across an armature air gap between said spaced apart rotor portions, and circumferentially through each of said rotor portions. The stator includes an air core armature supported in the armature airgap, and has a non-ferromagnetic structure where located in the magnetic flux in the armature air gap. Three phase windings wound on the armature magnetically exert torque upon the rotor when the windings are electrically energized by the electronic drive. The phase windings are wound from wire that is formed from bundled together multiple individually insulated conductor strands, wherein said strands are electrically connected in parallel and are electrically insulated between each other along their lengths where they lie in the magnetic flux in the armature airgap. The electronic drive is configured to convert electrical supply power into power that is synchronous with the rotor rotation by regulating power through a switch mode converter that varies voltage to a variable DC link supplying a transistor output H-bridge for commutating the phase windings. The electronic drive electrically energizes only two of the three phase windings simultaneously to provide trapezoidal excitation to the phase windings, leaving one of the three phase windings instantaneously electrically non-energized. The electronic drive monitors the instantaneous non-energized phase winding back-emf zero crossing events for controlling triggering of advances in the commutation.