We are installing a wye primary, delta secodary transformer to boost a 120/208 volt source to 480 volts 3 phase to serve a chiller. Should we ground one corner of the 480 volt delta? It seems to me we need to in order to get overcurrent protection to clear a ground fault on the 480 volt side.
corner ground delta
- Thread starter GT500
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brian john
Senior Member
- Location
- Leesburg, VA
If it was me I get a 208 delta to 480/277 wye XMFR...Simplify the installation espically for the next guys. Other wise IF YOU MUST use this transformer either corner ground or install a ground alarm.
dennis schaffert
Member
ground fault
ground fault
Can anyone explain to me how grounding one leg of a delta secondary clear the ground fault on a primary .this question makes no sense to me. Add danger to danger perhaps
ground fault
Can anyone explain to me how grounding one leg of a delta secondary clear the ground fault on a primary .this question makes no sense to me. Add danger to danger perhaps
- Location
- Massachusetts
dennis schaffert said:
It won't.
Any ground faults on the primary side need to be cleared by bonding on the primary supply system or by electricians notified by ground fault alarms.
I can't explain it either. It appears to me that corner grounded 480D is about as poor as one can do. Ungrounded 480 delta has some issues with arcing ground faults, that have to be mittigated. If I had to use a 480V Delta secondary, I'd investigate a zig-zag or wye-delta ground transformer. - or leave it ungrounded.dennis schaffert said:
carl
brian john
Senior Member
- Location
- Leesburg, VA
Unless you are using a used transformer or all ready purchased what IMO is the wrong transformer for the application, 208 Dela to 480/277 wye (depending on size0 is readily available.
While it is NEC compliant I dislike it. In reality I should like it, over the years I have made money troubling shooting and in several instances replacing these systems when the end users could not figure out the STRANGE voltages, and when the situation was explained disliking the installed system.
While it is NEC compliant I dislike it. In reality I should like it, over the years I have made money troubling shooting and in several instances replacing these systems when the end users could not figure out the STRANGE voltages, and when the situation was explained disliking the installed system.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
When I feed single pieces of equipment I use an ungrounded systems. When I need to feed a distribution panel use corner grounded.
The only time I use a 208-480Y transformer is when I need the 277V connection. I prefer to use off-shelf equipment whenever possible.
The only time I use a 208-480Y transformer is when I need the 277V connection. I prefer to use off-shelf equipment whenever possible.
brian john
Senior Member
- Location
- Leesburg, VA
Jim I have bought 480/277 wye transformers without a special order* from Square D, has bee a year or so. I have stated my beliefs and why, the rest is up to the end user (if they know and understand) designer and installer.
* These were not stock at my supplier but were shipped next day from the factory.
* These were not stock at my supplier but were shipped next day from the factory.
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