Transformer temperature rating (high secondary output)

[journeyman0217]

A normal megger will not find turn to turn shorts.

What size is this transformer? I don't think I have ever seen a 30kVA and larger without some type of taps.

yes, i misspoke. It does have multiple taps for HV. tap 3 is for 480 and that is what it's tapped to. it's a 75kva xfmr

 

[jim dungar]

yes, i misspoke. It does have multiple taps for HV. tap 3 is for 480 and that is what it's tapped to. it's a 75kva xfmr

The quick fix is to change the taps to lower the output voltage.
This does not solve the problem with the turns ratio.

When you measured the conductor temperature were you at the field conductors?
Just for giggles, what is the surface temperature of the transformer enclosure? Some eople think single IR Scans of the exterior provides meaningful data.

 

[journeyman0217]

The quick fix is to change the taps to lower the output voltage.
This does not solve the problem with the turns ratio.

When you measured the conductor temperature were you at the field conductors?
Just for giggles, what is the surface temperature of the transformer enclosure? Some eople think single IR Scans of the exterior provides meaningful data.

i measured the surface of the transformer and it was around 95F. Took the cover off and it was like opening an oven door getting hit with the heat. The coils were around 215F. The conductors were 215F right off the taps but dropped quickly as I scanned exiting the transformer.

After doing this scan, I would def say doing exterior scan is not meaningful to a degree

 

[jim dungar]

After doing this scan, I would def say doing exterior scan is not meaningful to a degree

They can be meaningful when used to create a trend, just not as one off troubleshooting.

Based on your temp readings, my first thought is your transformer is not overheating, unless it is lightly loaded.
But you need to check out the turns ratio problem.