Transformer Impedance

[tryinghard]

What would be a common impedance percentage of a 480-120/240 112.5 KVA cu wound dry type transformer?

I want to calc the available fault current without calling the manufacture, at least get it close for design purposes if I can.

 

[mivey]

Why not call?
4.3% would be a fair guess

 

[tryinghard]

I'm not purchasing just designing, our purchasing will have to call and it's not likely going to happen, I don't know who they'd use. Otherwise I agree I'd call.

I have a 83 KVA calculated load and there's no way I would buy a transformer without giving the site specific spes to the manufacture.

 

[mivey]

If you wind up being close on the AIC, I would bump it up. It kind of depends on what you are doing with the source impedance.

You could always call 2 or 3 manufacturers and use the worst case.

 

[mivey]

You may find this useful as well:
See table 14 on page 43

http://www.geindustrial.com/publibrary/checkout/White%20Papers%7CGET-3550F%7Cgenerichttp://www.arcadvisor.com/pdf/GET3550Fapp41-43.pdf

 

[zog]

Here is the closest one to that I had out back.

150kVA HV - 480V LV - 208/120V CU

Z = 3.7%

 

[mivey]

Here are specs for GE TP-1 transformers:

http://www.geindustrial.com/publibrary/checkout/Application%20and%20Technical%7CE-DET-488%7Cgeneric

and the selection guide:

http://www.geindustrial.com/publibrary/checkout/Catalogs%20and%20Buyers%20Guides%7CXFMR-1%7Cgeneric

 

[QuestionGuy]

Transformer Question

Transformer Question

The System Discription:
Need to provide 480V/3ph with less than 160 milli-Ohms of resistance.

The installed system
Building service = 120/208V 3ph 4w --> 75KVA X-former (5.11% @ 170C) --> 480/277V 3ph 4w

I am measuring 11 m-ohms on primary side & 261 m-ohms on secondary.

What %impedance do I need to achieve < 160m-ohms?
Will a 112.5 KVA X-former achieve this?
Do I need a 150KVA ?