Transformer runs hot. whats the problem

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Jeff80

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I have a few transformer is the same electrical room and one runs hotter than the other.
Here is the info

Line side fused at 70amp
14.1amp 286volt
12.oamp 284volt
10.5amp 287volt

Load side breaker 150amp
27amp 123volt
30amp 122volt
18.5amp 123volt

All the terminations in the panels are 77-88 degrees F. (i didnt open trans)
The top of the transformer is 140-150 degrees F. The transformer is 30 years old and right up against a wall.

Is this ok to be that temp constantly. should I pay for an infared
 
Without knowing how loaded the transformer is, it is not possible to accurately evaluate your situation. But from the numbers you have provided, I would not suspect a problem.

The coolest maximum termination requirements I know of are about 40?C (104?F). I would not be surprised to find the top of a fully loaded transformer core and coil (inside of the enclosure) to be close to 190?C (374?F).
 
Jeff80 said:
I have a few transformer is the same electrical room and one runs hotter than the other.
Here is the info

Line side fused at 70amp
14.1amp 286volt
12.oamp 284volt
10.5amp 287volt

Load side breaker 150amp
27amp 123volt
30amp 122volt
18.5amp 123volt

All the terminations in the panels are 77-88 degrees F. (i didnt open trans)
The top of the transformer is 140-150 degrees F. The transformer is 30 years old and right up against a wall.

Is this ok to be that temp constantly. should I pay for an infared
Click to expand...

That's barely warm. You're fine.
 
If it is a Dry-Type transformer, it probably has 220 deg C Insulation (nameplate will say).
40 deg C Ambient plus 150 deg C Rise gives you 190 deg C. That still gives you a 30 deg C cushion before you reach the ultimate 220 deg C.
You're in good shape.
It should be away from the wall a bit for air circulation, but with the low current readings - not too worried. (why should I worry - it's not my transformer)
It might need to be vacuumed out.
Maybe check harmonics.
slainte
db
 
barclayd said:
40 deg C Ambient plus 150 deg C Rise gives you 190 deg C. That still gives you a 30 deg C cushion before you reach the ultimate 220 deg C.
Click to expand...

The 30?C cushion is actually called the hot spot allowance. The internal portions of the transformer will heat up more than the portions that are exposed to air movement. The 30? means that the 'internal' insulation will not be damaged even if the exterior gets to 190?C. You could consider this more like a 'safety margin' rather than a 'service factor'.
 
jim dungar said:
The 30?C cushion is actually called the hot spot allowance. The internal portions of the transformer will heat up more than the portions that are exposed to air movement. The 30? means that the 'internal' insulation will not be damaged even if the exterior gets to 190?C. You could consider this more like a 'safety margin' rather than a 'service factor'.
Click to expand...

Jim,
Never thought about it that way.
Makes good sense.
Thanks for the info.
:smile:
 
barclayd said:
Maybe check harmonics.
slainte
db
Click to expand...

Check the amps on your neutral (slight imbalance). also if you can perform a shut down, check all connections to make sure that they are tight as required, and clean (as noted by others). What type of loads are running off this Xfmr (Inductive, Resistive?) may have high harmonics as DB has indicated. Also what size (KVA) is the hot xfmr?

- JWC
 
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