Abstract: A transformer comprising columns, wherein each of the columns comprises a magnetic material, a length axis, an upper end, and a lower end, an upper yoke in contact with the upper end and a lower yoke in contact with the lower end, wherein at least yokes comprises two parallel sub-yokes and a yoke connector connecting the two parallel sub-yokes, at least one primary winding on at least one of the columns configured to produce alternating magnetic flux in a closed magnetic circuit defined by the columns and the yokes, at least one secondary winding on at least one of the columns, and at least one control winding on the yoke connector, wherein the at least one control winding is configured to produce direct magnetic flux in a closed magnetic circuit defined by the yokes and the respective yoke connector, wherein the respective yoke connector is in a magnetically symmetrical position.

Abstract: A polyphase transformer (1) comprising at least a first leg (2, 51) and a second leg (3, 52) of a magnetic material is described. The transformer comprises a single core with legs (2-4, 51-53) and yokes (27, 28, 54, 55). A primary winding (9, 15, 21, 56, 60, 62) is arranged on each one of the legs (2-4, 51-53) arranged to produce primary magnetic fields in the legs (2-4, 51-53), a secondary winding (12, 18, 24, 59, 61, 63) is arranged on each one of the legs (2-4, 51-53). The winding axis of the primary winding (9, 15, 21, 56, 60, 62) and the winding axis of the secondary winding (12, 18, 24, 59, 61, 63) are essentially parallel to each other on each one of the legs (2-4, 51-53). The transformer (1) also comprises at least one control winding (33-35, 45-47, 48, 49, 73-75) arranged to produce magnetic fields in each one of the legs (2-4, 51-53) being essentially orthogonal to the primary magnetic fields in the legs (2-4, 51-53).