A stator assembly for an electrical machine comprises a core made of a magnetic material. The core has an annular yoke (2) and a plurality of teeth (3) spaced circumferentially on the annular yoke and extending radially therefrom. The spaces between the teeth define circumferentially spaced winding slots (6). A stator winding is carried by the stator core and has coil turns located around the teeth and in the winding slots. Each tooth and a radially adjoining part (4) of the yoke have varying axial dimensions in order to adjust the magnetic flux to an optimal flux density in each part of the magnetic flux path in the stator. The annular yoke (2) may extend axially past the teeth (3) at least at one of the axial sides thereof.