Transformer comprising windings

The invention relates to a transformer comprising a core (112) and a winding (204) wound around a winding axis AW extending along a post of the core (112), the winding (204) terminating in an axial end face (207, 208) extending in a direction perpendicular to the winding axis AW, the transformer comprising a ring (205, 611, 705, 1705) comprising a magnetic material, the ring being located outside the winding (204) and adjacent to the axial end face (207, 208). The ring (205, 611, 705, 330, 530) comprises a set of magnetic metal components (331, 533, 534, 153), such as magnetic metal sheets, distributed around the winding axis AW and electrically insulated from each other. The core (112) includes a yoke (1200) that extends radially through the ring (205, 611, 705, 1705) from a radially inner side of the ring (205, 611, 705, 1705) to a radially outer side of the ring (205, 611, 705, 1705) at one or more intersection locations (1300). The cross-sectional height of the ring (205, 611, 705, 1705) varies about the