Patent ID: 6710581
Filing Date: 2004-03-23
Classification: H02K,H02P

Abstract:
A constant-power brushless DC motor, comprising:a stator wound in parallel by phases and polarities and configured of n multi-phases, each of the winding coils of the stator which are not connected with one another is connected to each of n full H-bridges, n full H-bridges are connected to a DC power supply in parallel; a rotor having a predetermined number of polarities, which is required to concentrate magnetic flux on excitation area; a commutation encoder including sensing regions and nonsensing regions, the commutation encoder being externally set to one side of the shaft of the rotor; and two photo sensors set to each phase, the two photo sensors being connected to a half H-bridge of each phase, to switch the half H-bridge on and off, wherein the width of each of the sensing regions of the commutator encoder is determined to allow a phases among n phases to be excited constantly, the corresponding photo sensors recognizing the a phases excited, wherein the stator has narrow slots to remove flux cancel phenomenon between every winding slot and to remove peak current between said excited phase and said inexcited phase, and wherein the number of phases among the n phases, which will be excited, is determined by the distance between the sensing regions, the distance between the sensing regions being determined through the following expression, width of sensing regions=(2&pgr;Ã—number of phases to be excited)/(number of polarities of rotorÃ—number of phases of motor) (Â°), the number of sensing regions in the commutation encoder being determined through the following expression, number of sensing regions=(number of polarities of rotor)/2, the distance between the photo sensors on a sensor plate being determined by the following expression, distance between photo sensors=2&pgr;/(number of polarities of rotorÃ—number of phases of motor) (Â°), among the n phases, a phases being excited but b phases not being excited all the time.