Patent ID: 6359401
Filing Date: 2002-03-19
Classification: H02K

Abstract:
A multi-phase bipolar brushless D.C. motor comprising: a stator constituted by M phases, each phase having a plurality of windings connected in parallel and further connected independently of the winding connection of the other phases;a rotor shaft rotatably coupled to said stator and having N embedded permanent magnet poles which concentrate flux between opposing faces of like polarity; a commutation encoder fixed at one end of the rotor shaft comprising a circular plate and an annular ring defining at least one light shielding portion which functions as a non-sensing area, and at least one light detecting portion having opposite vertical edges which functions as a sensing area; photo-sensors coupled operatively with the commutation encoder and being constituted so that two photo-transistors are provided with respect to each phase, each of the photo-transistors in the M phases being arranged, in turn, and one by one at intervals of predetermined shaft angle so as to produce a positive pulse when registered with the sensing area of the commutation encoder; an electronic commutator constituted in such a manner that four power transistors are connected across the windings of each phase of the stator, two of the four power transistors of each phase being connected to one of the photo-transistors so that each phase is provided with two photo-transistors in order to perform the determination of the current direction according to the positive pulse of the photo-transistors, thereby flowing the alternating current through the windings to drive the motor; and an electric power source connected in parallel to each phase of said electronic commutator; wherein the width of the light detecting potion is determined by the following formula: 2&pgr;/ the number of polesÃ—(the number of phasesÃ—K/the number of phases), wherein K is the commutation coefficient; the number of the light detecting portions is determined by the following formula: (the number of poles)/2; and the interval between each of the photo-transistors is determined by the following formula: 2&pgr;/(the number of poles)Ã—1/(the number of phases); whereby the motor can be composed of one selected from a group consisting of 2-phase with 1-x-exciting, 3-phase with 2-y-exciting, 4-phase with 3-z-exciting . . . n-phase with (nâˆ’1âˆ’j)-exciting, where x, y, z and j are fractional commutation coefficients, thereby raising the efficiency, power, and speed of the motor.