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Reply To: Transformer riddle no.2 – Power transformer with inferior core

#1153
BertHickman

    The capability to withstand short circuit forces is a function of the design, materials, and construction technique. It’s not clear that the core material would play a direct role in short circuit strength, since the forces are primarily between the windings themselves. The alignment of primary versus secondary windings is quite critical to prevent excessive axial forces and the coils must also be sufficiently preloaded during manufacture via rigid clamping. Was the damage to an inner winding (i.e., bending/crushing) or was there radial shifting of the outer winding from tensile force (hoop stress)? Does the transformer use circular or rectangular shaped windings – circular windings can withstand short circuit forces with less deformation. Was there twisting of disk winding conductors? Were the windings made from copper or aluminum alloy, and were they properly specified and/or heat treated? Was the pressboard material prestabilized, high density and within specification (for percent compression) to provide sufficient rigidity? Do you have any pictures of the damaged areas? Unfortunately, identification and correcting the problem(s) would require significantly more information that you have provided.