Why did the wires burn on the transformer TMO?

Hello! When asking questions, please write clearly and completely, why should we guess what is at stake?

And here we are talking, if I understand correctly, about a transformer for heating concrete. Cables are burned for one reason - increased heat. The reasons may be different heating:

1. Too much current. Take a cable with wires of a larger cross section.
2. Short circuit - actually at this moment also a very high current.
3. Incorrect installation, for example, when a cable is used rolled up into a ring or a bunch of cables are piled up, all are loaded, heated and do not cool.
4. Poorly tightened pins. They are warming, warming and veins as a result of isolation peeling off.