Abstract: A rotor disc assembly 10 for an AC machine includes a rotor disc 20, permanent magnets 30 and a spider 40. The rotor disc 10 has a circumferential lip 22 projecting from a surface thereof. The permanent magnets 30 are positioned in a circular array on the surface of the rotor disc 20, with constant angular pitch, and so as to lie against the lip 22. The spider includes an annular base portion 41, with a plurality of arms 42 projecting radially outwards therefrom. The spider 40 is fixed to the surface of the rotor disc 20 such that each arm 42 is between and abuts a respective juxtaposed pair of the permanent magnets 30. The arms 42 and the members 30 are each provided with cooperating wedge-shaped cross sections such that each arm 42 constrains the respective two permanent magnets 30 both axially and tangentially on the surface of the rotor disc 20.

Abstract: A rotor disc for an electrical machine is disclosed. The rotor disc comprises a series of magnetisable members arranged in a circumferential series on a surface thereof and against peripheral retaining structure of the disc. The disc also includes a retainer fixable to the surface and arranged for assisting in retaining the members at least axially on the surface when so fixed. The retainer is arranged to abut at least one of a substantially circumferentially and substantially tangentially extending, radially inner part of each member and thereby to provide the axial retention.

Abstract: A toroidal AC generator includes an outer casing and an annular stator core of ferromagnetic material which is encased in a hollow annular cover of plastics material and which is fixed to the casing between the discs of a twin disc rotor. Each rotor disc carries a circular array of alternately polarised permanent magnets which face the stator core. The hollow annular cover is a two-part moulding and is formed of radially inner and outer ring portions which are joined by circular arrays of radial ribs which extend across the opposed radial faces of the annular core and form open-ended radial passages for the electrical phase windings which are wound around the cover. The ribs project radially beyond the radially outer ring portion and form hooks around which a winding may be retained temporarily during winding.

Abstract: A toroidal AC generator includes an outer casing (11) and an annular stator core (33) of ferromagnetic material which is encased in a hollow annular cover (34) of plastics material and which is fixed to the casing (11) between the discs (14 and 15) of a twin disc rotor (10). Each rotor disc (14, 15) carries a circular array of alternately polarised permanent magnets (23 and 24) which face the stator core (33). The hollow annular cover (34) is a two-part moulding and is formed of radially inner and outer ring portions which are joined by circular arrays of radial ribs which extend across the opposed radial faces of the annular core (33) and form open-ended radial passages for the electrical phase windings which are wound around the cover (34). The ribs project radially beyond the radially outer ring portion and form hooks around which a winding may be retained temporarily during winding.

Abstract: A rotor disc assembly (10) for an AC machine includes a rotor disc (20), permanent magnets (30) and a spider (40). The rotor disc (10) has a circumferential lip (22) projecting from a surface thereof. The permanent magnets (30) are positioned in a circular array on the surface of the rotor disc (20), with constant angular pitch, and so as to lie against the lip (22). The spider includes an annular base portion (41), with a plurality of arms (42) projecting radially outwards therefrom. The spider (40) is fixed to the surface of the rotor disc (20) such that each arm (42) is between and abuts a respective juxtaposed pair of the permanent magnets (30). The arms (42) and the members (30) are each provided with cooperating wedge-shaped cross sections such that each arm (42) constrains the respective two permanent magnets (30) both axially and tangentially on the surface of the rotor disc (20).