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Anonymous Poster

K-rating selection

06/17/2010 12:59 AM

If a 2500KVA transformer connected to 2 nos 900kW compressor with VFD starters, what is the non-linear load we consider?..Since the two 900kW VFDs are there, do we have to consider the VFD load will create the harmonica?..What will be the K-rating of Transformer if we want select the K-rated transformer to withstand the heat due to the harmonics?....
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electricalexpert65
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Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#1

Re: K-rating selection

06/17/2010 7:49 AM

Please visit this website: www.leonardo-energy.com

They have a wonderful guide on K-Rated Transformers.
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msamad
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Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#2
In reply to #1

Re: K-rating selection

06/17/2010 9:46 AM

Electricalexpert65:

For the curiosity, I was looking the website that you provided and browsed most of the links there but didn't find anything of K-factor selection guide. Is there any specific link you know that I can find it?

Guest:

Did you have chance to look into the immediate previous thread (http://cr4.globalspec.com/thread/55995/K-Rated-Transformer) and go through the links that I provided? Didn't you find your answer there?

Since you have 100% of the loads non-linear, you should select a transformer of K-factor 20 or a regular transformer with almost 30-35% de-rated. However, I would suggest you to consult the VFD vendor for the transformer selection recommendation.

- MS

__________________
 "All my technical advices in this forum must be consulted with and approved by a local registered professional engineer before implementation" - Mohammed Samad (Linkedin Profile: http://www.linkedin.com/in/msamad)
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electricalexpert65
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Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#3
In reply to #2

Re: K-rating selection

06/18/2010 9:38 AM

I am sorry I mentioned the wrong link. It is Copper Development Association's Publication No. 144: "Harmonics, Transformers and K-Factors". The web link is: www.cda.org.uk . Happy browsing.
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