The Z (impedance) for Transformers

[Golestan]

Hi,
Is there a table or common values for Z, used in short circuit calcs for typical dry type standard transformers. Example 15 KVA, 25, ... up to 125 KVA. 480v primary to 220v/110v secondary. Or, does it have to come from the power co. or manufacturer?
Regards,

 

[rbulsara]

Actual values have to come from the manufacturer. In fact they can provide you some typical values for "their" products.

More defined ANSI/IEEE stadards (for North America) exist for transformer rated 500kVA and greater. For smaller units, I am not aware of any standards ( that does not mean they do not exist), but the Z of smaller transformer varies greatly between manufacturers and type.

Typically Z of smaller transformer you describe range anywhere between 1.5% to 3%.

 

[cuky2000]

See the enclose link for reference impedance values

http://cuky2000.250free.com/Dry_transformer_Impedance1.jpg

 

[alehman]

See page 153 of the following document for this manufacturer's typical values.

http://www.eatonelectrical.com/unsecure/cms1/TB00900001E.PDF

 

[peebee]

ANSI (C57.12, I think... I don't have it in front of me) lists "preferred" or "suggested" transformer impedance values.