Effect of Artificial Burrs on Local Power Loss in a Three-Phase Transformer Core

The increase in losses due to burrs occurring on cut edges of electrical steel laminations in transformer cores is difficult to quantify. Artificial burrs were applied to a 350 kVA, three-phase, five packet, transformer core. Total core loss, flux density distribution and local loss near the burrs were measured. Burrs applied to a portion of a packet of laminations in one limb caused the flux distribution to become more nonuniform than normal throughout the whole core. Local losses increased significantly outside the burr region. The loss increased to over 1000 W/kg in the severely burred region at 1.8 T, 50 Hz. Measured flux distribution data was used in simplified eddy current calculations to predict the total and localized losses. The predicted and measured localised losses in the burred regions followed similar trends but did not agree well in magnitude probably due to the errors caused by the simplifications and assumptions which were necessary in the eddy current analysis.