Add fans to transformer

We have a 480-208/120v, [pre][/pre]1000/1333 KVA transformer with load running close to its OA rating. We decided to install custom made fans, such that air is forced to go through windings. I know this might not equal it's FA rating, but how can we calculate new rating? we can measure all peremeters including KVA, current, temperature...etc.

 

[GroovyGuy]

I am surprised that the forced-air ratings are not provided on the NP. I would suggest that you ask the OEM for the ratings. Don't forget that these ratings are also affected by the ambient temperature, insulation class and temperature rise.


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[davidbeach]

FA ratings only exist when the transformer manufacturer designs the FA system.

 

[EngSnow]

Thanks guys. The FA rating is 1333 KVA, but as David beach said, this only true when we use vendor provided fans. My question is, if we know know the difference in temperature those fans provided, can we calculate the new rating? For example, if we able to lower the temp by 20 degree C, how much KVAs did we gain? I guess I can look at KVA Vs Temp graph, and figured out a correlation that way...any thoughts?

 

[prc]

I think you are considering dry type transformers. Here normally they use special fans and blow air upwards through the gap between HV and LV windings. You must get guidance from the OEM. As regards loading margin for lower temperature rises etc, please refer loading guides for dry type Transformers. Refer to IEC 60076-12(2008) or C57.96-2013

 

[stevenal]

Perhaps I'm missing something here, but you cannot force air through the windings of an oil filled (OA/FA rated)transformer. Air doesn't have sufficient dielectric strength.

 

[GroovyGuy]

Howdy Steve,
I understand that the transformer in question is a dry-type, and not oil-filled.
GG


"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)

 

[stevenal]

OA stands for Oil-Air, both unforced without the F. A dry type would have AA/FA ratings with the AA meaning ambient-air.

 

[unclebob]

Select a max temp, say 150C. Don't go over the max temp on the nameplate.
Add load until you reach that temp, with fans running.

To be on the safe side, put 4 fans per winding, 2 on the front, 2 on the back, for a total of 12.