Manufacturing fault or user misuse on a failed transformer?

After a transformer caught fire, the user blamed the manufacturer and the manufacturer blamed the user for misusing their product. Root cause analysis was required, which included the disassembly of the transformer’s winding by hand.

As each winding layer was removed, it was observed that the conductors had been dropping down and riding up (due to the inherent vibration of the transformer action) between layers thus causing numerous weak points throughout the winding. As the first winding layer was revealed, it became apparent that the winding former had melted and that one of the winding conductors was open circuit between the first and second layer creating an interlayer fault with the corresponding turn on the second layer as shown in the photograph here. The “start lead” of the winding conductors was 30mm short of where the conductors went round the former corner. It was therefore confirmed to be a manufacturing fault.

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Neal Courtney, Managing Director

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Mobile: +44 7585 445882


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Surrey TW10 6TF


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