Cooling and external rotor electrical generator

An electrical generator comprises a stator 700 comprising one or more electrical windings and a rotor 650 comprising one or more permanent magnets, the rotor is arranged to be rotatable with respect to the stator about an axis of rotation wherein the rotor is located further from the axis of rotation than the stator. The arrangement of the rotor is such that electromagnetic forces acting between the rotor and elements of the generator radially outside the rotor are substantially zero. A Halbach array of permanent magnets may be employed. The rotor and stator are mounted coaxially on the axle which may be fixed with respect to the stator, the rotor bearings electrically isolating the rotor from the stator. Stator wiring leads may pass though holes in the axle. The stator coolant manifold 820 may be connected to a coolant fluid system by means of flow and return pipe 660,862 which pass though holes 864 in the axle.