Multi-phase bipolar brushless D.C. motor

Claim 1

A multi-phase bipolar brushless D.C. motor comprising: a stator constituted by M phases, each phase having a plurality of windings which are connected in series and being connected independently of the winding connection of the other phases; a rotor rotatably coupled to said stator and having N permanent magnet poles; a commutation encoder fixed at one end of the rotor shaft outside the motor and assuming a cylindrical form comprising a circular plate and an annular ring, said annular ring having light shielding portions and light detecting portions which function, respectively, as non-sensing and sensing area, and each of said light detecting portions having opposite inclined portions, which is inclined to the edge of said light shielding portions at a given angle; a photo-sensor coupled operatively with said commutation encoder and being constituted so that two photo-transistors are provided with respect to each phase, each of said photo-transistors in said M phases being arranged, inturn, one by one at intervals of predetermined shaft angle so as to produce a positive pulse when registered with said sensing area of said commutation encoder; an electronic commutator constituted in such a manner that four power transistors are connected across the windings of each phase of said stator, two of siad four power transistors of each phase being connected to one photo-transistor of said photo-sensor so that each phase is provided with two photo-transistors so as to perform the determination of the current direction according to said positive pulse of said 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.