Wiring a code compliant transformer

[qcroanoke]

We have a 45 KVA 380 delta 50 hz 3 phase primary to 220/127 wye 50 hertz 3 phase secondary
transformer. primary amps are 68.4 secondary amps are 118.
By code what size should my OCPD be on the primary?
It will feed a UPS off the secondary that is not going to be more than 10 feet away.
Is a secondary OCPD required?
It is a dry type transformer
class AA
150 C. rise
K factor 4
Mfgr. OLSUN Electrics Corporation
Thanks for any help.
I'm not well versed on Xfmr's.

 

[augie47]

Allow me to "verse" you a bit.
You need to concerned with 4 articles primarily, Art 450, 240, 250 and, of course 310.
Art 450 will provide you with the info to properly protect the transformer.
Normally (if there is such) you will have secondary OCP at 125% of the transformer output and primary protection no greater than 250%.
Once you select the OCP devices based on that, size your conductors accordingly using 240.21(C) and Art 310.
A 220/127 Wye secondary will require secondary OCP.
Typically your 45 kva would probably have a 125 amp or 150 amp OCP on the secondary and somewhere in the neighborhood of a 100-125 amp primary.
Be sure to look at 250.24 for grounding.

(hopefully my math is correct)

 

[jumper]

I keep this MH transformer example as a bookmark. It may help.

http://www.mikeholt.com/mojonewsarchive/NEC-HTML/HTML/TransformerInstallation~20020516.htm

 

[augie47]

Jumper, Great Link
Thanks