Transformer winding rise
Transformer winding rise
(OP)
I have a transformer with a 460v delta primary and a 460v y secondary. It is an isolation transformer. It is 220kva 3 phase, winding rise 150 deg c, 5.20% impedance @ 170deg c.
What does the winding rise mean?
Thanks.
What does the winding rise mean?
Thanks.






RE: Transformer winding rise
RE: Transformer winding rise
RE: Transformer winding rise
Winding temperature becomes more of an issue with larger transformers, particularly those that use cooling systems to allow more capacity than the self cooled rating of the transformer.
RE: Transformer winding rise
1 - with transformer secured at known ambinet temperature.
2 - With transformer operating at steady temperature, deenergize and immediately measure resistance.
To the extent the winding has not cooled down, you can use the ratio of the two resistances to infer the temperature based on copper temperature coefficient of resistance.
To get fancier you can log resistance vs time after deenergization and use that info to project back to resistance (temperature) at the exact time of deenergization. The exponential decay of temperature rise after deenergization produces a straight line on a plot of log scale for temperature and linear scale for time.
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RE: Transformer winding rise
Actually, anything over 124 degrees Fahrenheit will cause an instant skin burn. Slightly lower temperatures will cause a first degree burn after prolonged contact - not recommended even for masochists.
If you are running this transformer at over about 60% load it should be fenced off or otherwise be barriered against direct skin contact.
Most dry transformers that supply say 120 volt outlets in say a retail store carry no more than 1/3 of full load. Hence, the directive from Department of Energy that dry transformers be designed to produce optimal efficiency at 1/3 load.
RE: Transformer winding rise
Measuring resistance to determine average winding temperature is not just a theory, it has been widely practiced for years by transformer and motor manufacturers.
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RE: Transformer winding rise
Don't forget that scientific "theory" refers to something well established, and is not the same as "hypothesis." Sorry to rag on you, but this distinction seems to be getting lost these days.