What caused the transformer in the pump control panel to burn out?

A sewage pump control panel suddenly suffered a catastrophic failure—the control transformer literally caught fire and burned to a charred mess, completely catching us off guard. With no spare parts available in the warehouse and work needing to continue, we had to think fast.

From the circuit diagram, it’s clear that this pump control panel operates on a 660V AC power system, but its control circuit still uses 220V AC—essentially the same as standard distribution panels. The burnt-out transformer’s sole function was to step down the 660V AC supply to 220V AC to power the 220V AC contactor.

Understanding this principle made troubleshooting straightforward. Since our lighting system already provides a reliable 220V AC source, we decided to repurpose it as the control power supply for the pump panel.

We acted immediately:

• Ran a temporary cable from the lighting distribution box,

• Connected it to the output side of a residual current device (RCD) in the lighting panel,

• Powered up the system—and the pump operated normally!

Problem solved!