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Hello Wrenches,<br><br>
Does anyone have any insights on utility transformer sizing. We are
building a micro grid and connecting two, 200 A services, which are each
currently fed by15 kVA transformers. Ohm's Law says that these
transformers would be able to supply 62.5 A at 240 V. A 200 A
service requires a 4/0 AL feed. The transformer can supply 31% of
the service rating.<br><br>
The upgrade is to a 400 A service. The transformer is rated at 37.5 kVA,
which would produce 156.25 A at 240 V, and will require 350 kcmil AL
cable. This transformer will supply 39% of the rated 400 A.<br><br>
This could only make any sense with fully imbalanced loads at nearly max
output, and we are required to balance the phases. The larger loads are
supplied by 240 V. Even in a fully imbalanced condition, the main
breakers would trip to clear any overloads if the 37.5 kVA transformer
were run to a 200 A service. <br><br>
Is there really a good reason for these specifications? <br><br>
Thanks,<br><br>
Drake <br><br>
<a name="_MailAutoSig"></a>Drake Chamberlin<br>
<i>Athens Electric LLC<br>
OH License 44810<br>
NABCEP Certified Solar PV <br>
740-448-7328<br>
</i><a href="http://athens-electric.com/">http://athens-electric.com/</a>
<br><br>
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