A compact electrical machine

An electrical machine comprises a combined magnetic gearbox and electrical generator. A first set of permanent magnets (30) are arranged on a rotor (16) to produce a spatially variable first magnetic field. A second set of permanent magnets (32) are arranged on a rotor (40,41,43), stationary pole pieces (36) are positioned between the first set of permanent magnets (30) and the second set of permanent magnets (32) to interfere with the first magnetic field. Rotation of the rotor (16) relative to the pole pieces (36) produces a second magnetic field which rotates the second set of permanent magnets (32). A stator (42) has windings (46) to transduce a changing second magnetic field produced by the rotation of the second set of permanent magnets (32) into an electrical voltage. The electrical machine is useful for a wind turbine generator. Alternatively the arrangement may be modified to produce an electrical motor.