Abstract: A rotary generator comprises a rotor within a stator having end windings, the rotor defining a flow path for cooling fluid which, during rotation of the rotor forms an annular layer in the rotor. A cooling fluid feed means is provided having an inlet which, in use, is positioned within the annular layer of cooling fluid whereby a head of cooling fluid is formed at the inlet. The feed means defines a duct through which the cooling fluid passes by the action of centrifugal force towards an outlet from which cooling fluid is directed onto the end windings. The rotation of the rotor causes the head of fluid at the inlet to reduce with increasing rotational speed thereby effecting control of cooling fluid flow through the feed means as the rotational speed of the rotor increases.