GB619837A - Improvements in dynamo electric machines - Google Patents

Abstract

619,837. Permanent magnet machines. MANDL, A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Dec. 31, 1946, No. 38140. [Class 35] In a permanent magnet homopolar A.C. machine, the field members at each end of the permanent magnet have members providing a flux leakage path across an air-gap in parallel with the working flux circuit, and means are provided for closing this air-gap, the permanent magnet being magnetized in situ by means of a magnetizing winding. In the generator shown, the magnet 10, which may be of cylindrical form, or may be built up of a series of parallel bar-magnets, is located between yoke members 4, 7 which carry the flux to the rotor 1 and also through extending parts 8. 9, having flanges 13, 14, across the leakage air-gap 15. The rotor 1 comprises a toothed portion 2 co-operating with a laminated stator core 5 having output windings 6. The flux return path is by means of a small annular air-gap between an enlarged cylindrical flange 3 and the inner surface of the member 7. The magnetizing winding 16 is located concentrically round the magnet and before use the gap 15'is bridged by a magnetic ring. After magnetizing, this ring is replaced by a non-magnetic cover 24, so that the flux falls to a steady value, and the rotor placed in position. By this arrangement, removal of the rotor does not disturb the flux of the machine. A damping ring may be placed concentrically within the magnet. In a modification, the cylindrical air gap 3, 7 may be replaced by a further laminated stator core and corresponding rotor teeth, and the leakage gap may be closeable by adjustable means such as a screwed sleeve which may be used for automatic regulation of the machine output. The machine may alternatively have a permanent magnet rotor.