In-plane flux distribution in the mix 60o- 45o T-joint of three phase transformer core

Abstract

This paper describes the result of measurement of inplane flux distribution on 100kVA 3phase distribution transformer assembled with the mix 60o- 45o T-joint and mitred lap corner joint with stagger yoke of 10mm. The measurement involves the fundamental, third and fifth 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 60o-45o T-joint is 1.4T and rises to be 1.68T at the inner edges of 60o-45o T-joint when the transformer core energized 1.5 T 50Hz. Harmonic occurs mostly in the Tjoint 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.