In-plane flux distribution in 45o T-joint of 3phase transformer core with staggered yoke and limb 10mm

Abstract

This paper describes the result of measurement of inplane flux distribution on 100kVA 3phase distribution transformer assembled with 45o T-joint and mitred lap corner joint with stagger yoke and limb with overlap length of 10mm. The measurement involves the fundamental and third harmonic of the easy and hard direction of flux density at each location measurement. The flux distributions have been measured using no load test by arrays of search coil in M5 (CGO) grades material of transformer core laminations. The localised flux density at the outer 45o T-joint is 0.218T and rises to be 0.228T at the inner edges of 45o T-joint when the transformer core energized 1.5 T 50Hz. Harmonic occurs mostly in the T-joint where local regions are saturated and the flux deviates from the rolling direction. A small amount of flux deviation from the rolling direction occurs at the overlap, but no rotational flux is present in the joint.