GB950655A - - Google Patents

Abstract

950,655. Dynamo-electric machines; motors with commutation by semi-conductor devices; control of motors. COOK ELECTRIC CO. May 23, 1961 [June 6, 1960], No. 18610/61. Headings H2A, H2F and H2J. [Also in Division H3] A motor, Fig. 2, having a set of permanent magnet poles 30a ... 30f and a set of electromagnet poles 36a ... 36f arranged in concentric circles is characterized in that one set of poles is provided with asymmetrical projections 52 which project towards the other set, whereby the rotating set comes to rest out of alignment with the stationary set so that the motor will be self starting. Referring to Figs. 1, 2, each electromagnet stator poles 36a ... 36f of a 6-pole motor has two energizing windings 40, 42, which are energized alternately to produce the N and S poles. In an alternative construction, Fig. 3 (not shown), the projections are provided on the rotor poles. In order to provide the alternate energization of the electromagnet poles, the coils are connected in the collector circuits of two transistors connected as a reciprocally coupled trigger circuit (see Division H3) coils 42a, 42c, 42e and 40b, 40d, 40f in one collector circuit and coils 40a 1 , 40c 1 , 40e and 42b 1 , 42d 1 , 42f in the other. The circuits may be either astable to give continuous running, or bi-stable to give a stepping action. In a further arrangement, Fig. 9, for stepwise action, the coils are energized by connecting either of the above sets to the supply by means of a relay 282 with a change over contact 268. Alternatively, Fig. 13, the poles may be given a magnetic bias and the polarity may be reversed by energizing a single set of coils. The bias may be provided by means of a suitably magnetized ring 354 mounted at the end of the motor in contact with the cores 44 of the single coil windings. In an embodiment employing a commutator for switching the current to the coils, Figs. 10, 11, the two sets of coils are connected to fixed commutator segments formed by studs 308 and a brush 306 mounted on the rotor shaft is held by the action of spring 324 in contact with the commutator segments 308 and slip ring 316. Direction of rotation of the motor may be reversed by mounting the projections 376, Fig. 16, on a rotatable ring 380 so that they may be moved from the left-hand to the right-hand side of the poles.