Published transformer X/R ratios 1

[rockman7892]

Does anyone know where I can find published X/R ratios for transformer especially those in the kVA range? I looked in the IEEE Red Book and I only see a table for X/R ratios for transformers in the 1MVA range and higher and I was wondering if there was another reference that I am missing?

 

[dpc]

This should help (GE Publication GET-3550F):

http://www.geindustrial.com/publibrary/checkout/GET-3550F?TNR=White Papers|GET-3550F|generic

David Castor

http://www.cvoes.com

 

[rockman7892]

dpc

Thanks for the tables they are helpful!

Where does SKM reference its R and X values from? For a 75kVA dry type transformer I cannot seem to match the values given to any one of the attached tables?

 

[cuky2000]

See if the enclosed graph can help.

 

[rockman7892]

SKM gives a X/R ratio of about .875 for this 75kVA transformer. This seems lower then the above publisehd information.

Isn't there an IEEE standard for transformers that would give all of these typical X/R values?

 

[dpc]

http://standards.ieee.org/findstds/standard/551-2006.html

There might be something in here. I don't have the book, so I'm not sure. I generally use tables from Conrad St. Pierre's book.

The X/R can vary quite a lot on smaller transformers.

David Castor

http://www.cvoes.com

 

[jghrist]

SKM gives a X/R ratio of about .875 for this 75kVA transformer. This seems lower then the above publisehd information.

The X/R given in David's GE reference for a "QHT" 75 kVA dry type transformer (p.34) is 0.841. Cuky's graph shows a 75 kVA dry type data point with an X/R between 0.5 and 1. Seems like pretty good agreement to me.

 

[cuky2000]

For SC calcs. , the X/R range of the published values provide acceptable results for most practical purposes.

If you are doing any special application, that require high level of accuracy, I suggest to obtain the actual data of the specific transformer and work with the manufactor and test lab.