Transformer K-Factor

[rinezry]

Hi, was wondering if anyone can answer my question.

Is the k-factor for transformers applicable for dry type tfmrs only or do you have to consider it for liquid filled ones as well?

 

[Skogsgurra]

The k factor is the sum of(individual current harmonics squared times harmonic number squared). Harmonics in p.u. (1 = 100 percent).

It takes the effect of higher frequency components on copper losses as well as iron losses into account. It is used for power transformers of all kinds - dry or oil filled.

Fluke has some papers on this. There is also a discussion on

http://www.liebert.com/support/whitepapers/documents/sl_24200.asp

The k factor can be used to derate transformers - k-factor = 10 means that you shall derate a transformer around 20 percent. It can also be used to specify transformers. If you have a k factor = 15 and buy a transformer for 1000 kW at k factor 15, you will get a transformer that doesn't need to be derated.

Gunnar Englund

http://www.gke.org

 

[rinezry]

Thanks for that info.

Buying a couple of US-spec tfmrs for an offshore platform and the tfmr vendor's asking me what's the k-factor I want to use for the tfmrs. I reckon I can do away with k-1 or k-4 because 80% of loads are motors, but I reckon I should forward a copy of the load list to the vendor for him to judge himself what the best k rating would be.

 

[Skogsgurra]

Sounds right. Or, if you have a similar installation somewhere, make someone check the k factor with - why not? - a Fluke 41 or similar instrument.

Gunnar Englund

http://www.gke.org