GB311703A - Improvements in electric induction motors - Google Patents

Abstract

311,703. Sangamo Electric Co., (Assignees of Koenig, W.). May 14, 1928, [Convention date]. Alternating-current induction machines.- A single-phase induction motor, particularly a small self-starting motor for driving phonographs, clocks &c. comprises a. field coil from the opposite ends of which extend pole members having extensions which embrace the coil, a circular magnetic return path spaced from the, pole extensions by an annular air-gap, a cup shaped rotor arranged to rotate in the air gap, and means associated with the pole members to establish a rotating field in the air gap. As shown in Fig. 3, the casing forming the return flux path comprises a. cylindrical magnetic shell 14 held between non-magnetic end plates 15, 16 which are secured together by clamping screws. The front plate 15 carries a boss 25 of magnetic material upon which is mounted a coil 26. In the case of a four pole motor the coil is embraced by four U-shaped pole members as shown in Fig. 4. The two members 44, 45 extending from one end are separated by a copper or other ring 52, and a similar ring 53 is provided between the members 46, 47 extending from the other end. The purpose of these rings is to cause the flux changes in the pole members 44 and 47 to lag behind the flux changes in the members 45, 46. The pole-members and rings are held against shoulders 56, 56<1> on the core 25 and the stator assembly is secured to the plate 15 by rolling or spinning the ends of the core to form beads or flanges 57, 57<1>. The rotor 29 of copper or aluminium rotates in the gap 28 between the pole-extensions and the cover 14 and is secured to the shaft 32 between collars 33. The ends of the shaft are provided with pins 34, 35 which rotate in bearing plugs 36, 37, and the drive is taken from a pinion 42 located near a cut-away portion of the bearing sleeve 38. Constructions of pole-pieces for two, six and eight pole rotors are described. The conducting rings 52, 53 may be replaced by flat coils closed through a resistance or connected in series with the coil 26 and shunted by a resistance and a condenser.