Aspects of the present invention relate to a rotor arrangement (42) for a wind turbine generator (24). The rotor arrangement (42) comprises a cylindrical ring structure (46) arranged to rotate around a rotational axis. The cylindrical ring structure (46) comprises: a plurality of ring-shaped permanent magnet packages (48) arranged coaxially around the rotational axis, a plurality of tie rods (55) extending axially through the plurality of permanent magnet packages (48) to join the plurality of permanent magnet packages (48) together; and one or more spacer components (64; 164) located between at least one axially adjacent pair of the plurality of permanent magnet packages (48) to space the respective pair of permanent magnet packages (48) apart, wherein the one or more spacer components (64; 164) are configured to act as an impeller as the rotor rotates, in use, thereby to cause air to flow in a radial direction, with respect to the rotational axis of the rotor arrangement (42), between the at least one axially adjacent pair of permanent magnet packages (48). The generator rotor arrangement uses a portion of the kinetic energy of the rotating rotor arrangement to generate a radial air flow that flows between and/or around the magnet packages to transfer heat away from the magnet packages, and thereby to provide a cooling function.

A rotor for power driving includes a hub, a plurality of first fixed jibs, a plurality of second fixed jibs, and a plurality of outer vanes. The hub is adapted to be coupled with a shaft to rotate together in a single rotational direction. The first fixed jibs are arranged around the hub circumferentially. Each second fixed jib is engaged on an end of a corresponding first fixed jib. Each outer vane is elastically fixed at a corresponding second fixed jib and extends in a direction different from the single rotation direction when not acted upon by external forces such that the plurality of outer vanes, when acted upon by external forces, are elastically movable relative to corresponding second fixed jibs to drive the shaft to rotate along the single rotational direction and can rebound after removal of the external forces.