Question

You are using an external AC transformer to supply power to an electric fan. When you touch the transformer, it is very hot. What will you do? Why?

Answer 1

Reason 1:

• Check whether the current delivered to the load is within acceptable limits or not, if it is more than full load current then it may be the reason why the transformer is heating, in such a case just unnecessary load.

Reason 2:

• Check oil levels of the transformer and conservator tank, if less, then it may lead to transformer heating.
• Check the color and temperature of oil. If it has turned dark in colour, refill the transformer tank and conservator tank(transformer rating >500 KVA ) with freshly manufactured transformer oil. Fresh transformer oil is colourless as well as odourless.
• Even if oil hasn't turned dark in colour, atleast get oil filtered and tested(to ensure its ability to function as a dielectric) regularly, so that the dielectric strength of Transformer oil is restored.

Reason 3:

• Check for any short circuit faults, winding faults(can be determined by performing tests on the gases evolved from the transformer) and any other connection issues and resolve them. also check if the buchholz relay is functioning properly(for Transformers >500KVA).

Reason 4:

• Ensure that the transformer is installed correctly and appropriate arrangements for cooling have been made in order to avoid overheating in future.

If your problem still persists, go for a complete overhaul and rewinding.