Abstract: A fork autotransformer has a symmetrically arranged annular array of legs manifesting each phase of a three phase transformer. Each leg has a core about which three layers of windings are wound. The inner and outer windings are zig windings and the middle layer is a winding having one end connected to a junction of the zig windings as a power input and the other end connected to an end of the same winding of the other phases at a neutral point. Top and bottom yokes are magnetically coupled to, but are in electrical conductive isolation to, the cores. A Y-shaped clamp assembly clamps the yokes to the cores. The yokes are spaced from the cores to minimize even harmonic distortion using an insulating layer between the yokes and cores.