GB1054924A - - Google Patents

Abstract

1,054,924. Electric motors. NATIONAL RESEARCH DEVELOPMENT CORPORATION. Oct. 18, 1963 [Oct. 24, 1962; Sept. 17, 1963], Nos. 40325/62 and 36549/63. Heading H2A. In a synchronous induction motor having a squirrel cage rotor which synchronizes by virtue of having axes of high reluctance, the rotor has a plurality of circumferential magnetic segments 6 separated by comparatively narrow air-gaps 4. These air-gaps may be 1/10-1 times the circumferential extent of the segments, and are preferably about 1/6 to minimize the quadrature flux without reducing the main axis flux. A further improvement may be made by removing the inner corners 7 of the segments. The segments may be joined across the air-gaps 4 by thin bridges of metal stamping (Fig. 4, not shown) to provide mechanical strength. Improved performance may be achieved by cutting shallow channels or flats in the centres of the segments. It is also described (Fig. 5, not shown) how the segments may be located between salient poles and these may include radial slots. The segments may be secured by the cast squirrel cage. The rotor may be axially divided to permit the insertion of a conventional squirrel-cage section (Fig. 6, not shown)