Leakage reactance transformer

This specification discloses a leakage reactance transformer for supplying electric arc welding current and comprising a core formed from a stack of laminations having a central 'key-hole' shaped opening punched therein and defining an arcuate core portion and two spaced legs. The core has primary and secondary windings mounted thereon and a keeper secured to the legs to close the flux path of the core. One of the windings is mounted on a frame which is pivoted relative to the core so that the winding is movable along the arcuate core section towards and away from the other winding. A magnetic shunt member is also mounted on the frame approximately 180 DEG from the movable winding and in one position bridges the gap between the legs of the core and in another position is remote from this gap. In the bridging position the shunt contributes to the leakage reactance of the transformer and in the remote position contributes substantially no leakage reactance. The shunt is formed from a sector of the portion of the laminations cut from the core to define the arcuate section of the opening and the keeper is formed from the remainder of the portion cut from the core and defining the space between the legs of the core. The core and windings are mounted within a casing and means are provided to facilitate the pivotal movement of the movable winding and shunt to any position between the two extremes whereby the welding current may be infinitely varied between the values at the extremes.