Delta to Delta Transformer Grounding

Location
St. Louis, missouri
Occupation
Electrical Engineer
I have to step transformer 240-480V, 3phase. I am not sure the best approach is to ground the secondary either via corner grounding or if I should order as 480/277V service to a small panel in lieu of just a 480V panel. In essence I am feeding just (2) 480V, 3phase motors rated 3 hp.
 

jim dungar

Moderator
Staff member
Location
Wisconsin
Occupation
PE (Retired) - Power Systems
In my shop I would corner ground it. However if any 'general electrician' was going to work on it, I would use a 480Y/277V output, because it is a more commonly seen arrangement.
 
Last edited:

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
I would use a Wye secondary so that you can ground it. If VFDs are involved corner grounded might not be the best option.
 

petersonra

Senior Member
Location
Northern illinois
Occupation
engineer
I have to step transformer 240-480V, 3phase. I am not sure the best approach is to ground the secondary either via corner grounding or if I should order as 480/277V service to a small panel in lieu of just a 480V panel. In essence I am feeding just (2) 480V, 3phase motors rated 3 hp.
I am not a huge fan of corner grounding, mostly because it is pretty uncommon these days. Plus it complicates using vfds
 
Location
St. Louis, missouri
Occupation
Electrical Engineer
Thank you for your inputs. I will go with 480/277V. My electrician said he only needs 480. But for ease of the installation I was leaning toward 480/277V panel. Yes there are VFD involved.
 

winnie

Senior Member
Location
Springfield, MA, USA
Occupation
Electric motor research
Joining the chorus here. Use a 240V delta to 480/277V wye step up transformer. Your VFD equipment wants 480V L-L and 277V L-G. (I say L-G not L-N because N is not a needed circuit conductor, but the parasitics to ground are relevant. )
 
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