Need help with transformer

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Scater

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I have a 225kva transformer , I have wired it into a 440v panel with a 100 amp breaker and 1/0 wire . The second I energize the transformer it blew the breaker . There is no load on the transformer yet .
Any suggestions ?
 

augie47

Moderator
Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
If the 100 amp breaker is on your "440" primary, it's about 1/4 the size allowed. In all probability the transformer inrush current is tripping the breaker.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
If the 100 amp breaker is on your "440" primary, it's about 1/4 the size allowed. In all probability the transformer inrush current is tripping the breaker.

i agree, assuming the transformer is wired correctly.

A 225 kVA xfmr at 440V 3 phase is about 300 A at full load. I think you need to consider upping the Cb rating, which might well require you to increase the wire size. One other option might be to try and set the instantaneous setting on the breaker higher if it has such a setting.

Unless my calculator is wrong you would be allowed to use up to an 800A Cb on the line side.
 
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