Rotor cooling by inter-winding ducts; Cooling ducts in pole pieces

A spacing sheet is disclosed for forming cooling ducts between two layers of windings in the rotor of a rotating electrical machine. The spacing sheet comprises a backing layer (52; 115), and a plurality of spacers (54; 114) located on the backing layer. The spacers are discontinuous so as to define a plurality of interconnected cooling ducts. The pole shoes assist in retaining the windings, Figs 5,6 (not shown) illustrate differing lamination layouts. The laminations forming the pole pieces are of different size so as to define a radial exit path by recessing parts of the pole shoe for coolant flow 4 from the cooling ducts which are provided in an area of the winding which is overlapped by the pole shoe.