Method of fixing unmagnetised magnetisable members to a rotor disc and a rotor disc

摘要

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).