Transformer overheating

[john d]

How can you tell if a older transformer is overheating or getting ready to fail? I have a 225kva 480x208/120 dry transformer in a electrical closet. It is labeled as a 80deg rise. Using an infered camera i get readings of 240deg F. when looking at all 3 windings. The problem is it is only about 1/3 loaded. The air at the top near the vents is about 185deg F. This room has no real ventalation but i would expect a 80deg tx partly loaded to not be giving off much heat.

 

[zog]

How can you tell if a older transformer is overheating or getting ready to fail? I have a 225kva 480x208/120 dry transformer in a electrical closet. It is labeled as a 80deg rise. Using an infered camera i get readings of 240deg F. when looking at all 3 windings. The problem is it is only about 1/3 loaded. The air at the top near the vents is about 185deg F. This room has no real ventalation but i would expect a 80deg tx partly loaded to not be giving off much heat.

Are you looking at the windings themselves or the metal cover? You understand what reflection means? Are you a certified IR tech? If you are not actually reading winding temps your readings are meaningless.

You realize it is a 80C rise right? That means 176F above ambient, so if it is >64F in the room youae within spec, but again, I have a feeling you are reading the reflected tempature of the enclosure.

 

[kingpb]

Based on the temps provided, assuming they are being gotten in an appropriate manner, I'd say you are still within spec of the transformer, even though it's lightly loaded.

Meaning, given the conditions, that is probably going to be the maximum loading you can achieve without overheating. Which, the overheating will not cause the transformer to fail, per se, as it will reduce the life expectancy and cause a shortened life rather than catastrophic failure. Depending on the facility, shortened life could be viewed as catastrophic.

Sounds like the room could benefit from some airflow as a reasonable and cost effective fix.