autotransformer overheating

[oscar47]

What would cause an autotransformer to overheat after it has ran for long time? I have checked connections and sizes. It only overheats after more than 3 hrs of service.

 

[jim dungar]

What would cause an autotransformer to overheat after it has ran for long time? I have checked connections and sizes. It only overheats after more than 3 hrs of service.

What do you actualy mean by "overheating"?
How are you diagnosing this condition?

Fully loaded transformers can easily exceed 150?F skin temperature.

 

[oscar47]

The resin is melting out of the windings and the paper tags are turning brown.
I can smell the burn from 20' away. It only overheats after a period of time.

 

[mivey]

overload, poor ventilation, high ambient temps, harmonics.

 

[Adam A]

Check the ventalation in the area is there other equipment nearby also producing heat

 

[mxslick]

Add to Mivey's list an internal winding fault.

Check the total load on the autotransformer, if it is within the transformer's ratings, then simply replace the transformer.