Effect of stacking method and clamping on distribution transformers built with amorphous magnetic material

Work on stacked cores assembled from amorphous POWERCORE strip is described. The effect of the stacking method and clamping on power loss is shown. A 100 kVA, 3-phase, 3-limb core was assembled using a 105-mm-wide, 0.14-mm-thick amorphous POWERCORE strip. The core had 45 degrees -90 degrees T joints and 45 degrees mitred corner joints with 10-mm overlap lengths. It was built up to various stack heights with laminations stacked in single, double, and quadruple layers. It was found that the power loss increases with stack height and layer number. The localized power loss was 10% higher in a stack of 500 laminations than that in a stack of 100 laminations at 1.3 T. Use of aluminium clamps reduced the losses of the full size core from 0.43 W/kg to 0.33 W/kg at 1.35 T due to a reduction in stray flux or improvement in internal flux uniformity.<
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