Additional losses in three-phase transformer cores

Abstract

The influences of T-joint design and of the holes in yoke lamination on the magnetic properties have been investigated on scale models of three-phase three-limbed transformer core. Four variants of V-45° T-joint have been compared, and it has been found that they have virtually equal power losses, while the differences in magnetizing currents amount up to 60%. The variations of losses and magnetizing currents with hole diameter and flux density in the core are given. In distribution transformers of usual dimensions, a 2–4% increase of power losses due to holes in the yoke has been estimated.