GB1110340A - Improvements in dynamoelectric machines - Google Patents

Abstract

1,110,340. Permanent - magnet alternators; securing coils. GARRETT CORPORATION. 10 Sept., 1965, No. 38767/65. Heading H2A. In a planar air-gap machine with axiallyspaced rotary field structures, one of the structures has flux-producing means permanently magnetized in the axial direction and another is magnetically passive, providing a flux return path, the armature winding comprising a coil wound around one of the field structures with a portion of it located in the air gap. As shown in Fig. 8, an axially-magnetized annular magnet or set of magnets 3 (e.g. of alloy or barium ferrite) is secured to an iron flux-return disc 2 mounted on a shaft 1; spaced along the shaft is a further iron disc 2<SP>1</SP> providing the return circuit for flux across the planar air gap. Preferably, the assembly 2, 3 is encased in a shell 6, 8 (with thickened hub 7) of copper or aluminium to provide damping; preferably, fan blades 10 extend from back plate 8. Disc 2<SP>1</SP> is similarly clad and may also have fan blades. (For low-speed machines, only the damping on 2<SP>1</SP> need be present). The damping on disc 2<SP>1</SP> may be constituted by forming the air gap face of the disc into a pattern of axiallydirected protuberances, and casting aluminium or alloy in the intervening spaces, the damping being continued around the edge and rear face, where fan blades are provided. The air gap face thus formed may be further covered by a thin sheet of magnetic material to collect and distribute the flux uniformly (Figs. 6, 7, not shown). A stator comprising two coils 22 is fitted around the assembly 2<SP>1</SP>, 14, 15. Each coil is wound from round wire, the wires of each layer being located in the grooves between wires of an adjacent layer; the winding is then bonded. The outer portions of the two coils may be mounted between a plate 29 and vertical bars 28 of non-magnetic material, Fig. 13. In alternative coil-mounting arrangements, two non-magnetic brackets, which may be combined in one piece, are cemented to the coil, and the assembly is supported in a jig for drilling mounting holes in the brackets (Figs. 14, 15, not shown); alternatively, a plastics mounting-block may be used instead of brackets. Preferably, the ends of the coils are curved, in the plane of disc 2<SP>1</SP>, to follow the circular contour of the disc. For a two-phase machine two coil sets at right angles are provided, and for three-phase, three sets at 60- degree intervals.