K-rated transformers
K-rated transformers
(OP)
Is there a good resource for learning where and when to apply K-rated transformer and chosing the appropriate K factor? My training in is micro-electronics but I've been given 4 building electrical systems. Several areas here have non-linear loads that make up >50% of the transformer load & we just had a failure of a 75KVA 460-208 delta wye transformer. The transformer load is 100% SCR controlled test ovens which got me thinking harmonics took it out.






RE: K-rated transformers
Fluke has a good paper on this: http:/
Most transformer manufacturers give their view. This for instance: htt
Question about your failed transformer: Did it overheat? Or did something else happen?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: K-rated transformers
The transformer feeds a 225a 208v circuit breaker panel with 11 circuits. The loads are mostly 26A single phase environmental chambers. Before my meter died the current harmonics read ~75% triplen, ~50% 5th, ~33% 7th and ~15% 9th on a single load. I'll read the pdf from Fluke and, after the batteries recharge, get better readings.
RE: K-rated transformers
Alan
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"It's always fun to do the impossible." - Walt Disney
RE: K-rated transformers
120v, 208v or 120/208v? These can all be single phase.
What was the temperature rise rating of the transformer?
Can you take a photo of the transformer nameplate?
RE: K-rated transformers
Transformer is a standard Square D and the name plate is on the link.
RE: K-rated transformers
The transformer you have shown in your photo is 150 deg. C rise which is not the best for non linear loads. The high load losses and the additional heating from the harmonics push the thermal ratings.
RE: K-rated transformers