Transformer Burn Out Question
Transformer Burn Out Question
(OP)
Greetings,
I have a swimming pool UV Lamp sanitizer wall mounted 3 phase 6 KVA buck/boost transformer 480v Delta Primary to 208v wye secondary. It is wired with the pri. and sec. reversed 208 v wye pri. up to 480 v sec..
The amp draw (measured at 480v while in use) is Phase A 6.1A, Phase B 5.7A and Phase C 5.8A. The secondary (208v) has no connections on the X0 tap.
This trans. has been in use for about two years, the outside of the case measured about 232 degrees F, this thing has burned out with no sign of lightning or other componant failure. I am trying to figure out why it burned out so soon.
Any help is appreciated!!!!
jcall
I have a swimming pool UV Lamp sanitizer wall mounted 3 phase 6 KVA buck/boost transformer 480v Delta Primary to 208v wye secondary. It is wired with the pri. and sec. reversed 208 v wye pri. up to 480 v sec..
The amp draw (measured at 480v while in use) is Phase A 6.1A, Phase B 5.7A and Phase C 5.8A. The secondary (208v) has no connections on the X0 tap.
This trans. has been in use for about two years, the outside of the case measured about 232 degrees F, this thing has burned out with no sign of lightning or other componant failure. I am trying to figure out why it burned out so soon.
Any help is appreciated!!!!
jcall





RE: Transformer Burn Out Question
Dan - Owner

http://www.Hi-TecDesigns.com
RE: Transformer Burn Out Question
jcall
RE: Transformer Burn Out Question
Keith Cress
kcress - http://www.flaminsystems.com
RE: Transformer Burn Out Question
It is probably a good thing the neutral wasn't connected. We had a customer connect one just like this to feed 480V x-ray equipment from a 208V service. We had a phase to ground fault on our primary, cleared almost instantaneously by a fuse. Customer's wye-delta transformer (XO connected) continued to supply the ground fault until such time as X0-ground connection burnt open. Excessive currents in the delta damaged the transformer.
Like I say, best to use the proper transformer.
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question
jcall
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question
He also says the 5 kva is big enough to handle the load.
So the unit will be wired 3 phase 208 V wye supply to the transformer "secondary" 208 V wye side and will get 480 v Delta output to the load.
I am thinking about replacing it with a 9KVA unit so as to laod the transformer to around 65%, less load/less heat generated. Thoughts.....
jcall
RE: Transformer Burn Out Question
Buy a transformer with a 208V delta primary and 480V/277V star secondary. Earth the star point. Treat it as a separately derived source.
232F is about 111 celcius, not outrageously hot for a class F or class H winding. If you have a high ambient temperature make sure the transformer is adequately rated at the true ambient temperature with any covers on, panels closed etc. Elevated ambient temperatures require derating of the transformer.
----------------------------------
If we learn from our mistakes I'm getting a great education!
RE: Transformer Burn Out Question
Keith Cress
kcress - http://www.flaminsystems.com
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question
A 208V delta primary and 480V/277V wye secondary will be the replacement unit enabling star point secondary grounding.
Great to have all this knowledge available to tap into.
Much Thanks,
Jcall
RE: Transformer Burn Out Question
This could be producing quite a fair bit of mysterious hidden internal heating of the secondary.
Not sure if this is really the cause, but there are two solutions. Run the secondaries in open delta, with a 480v load directly across each winding.
Run the secondaries in star, with 480v phase to neutral, and ground the secondary centre point.
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question
RE: Transformer Burn Out Question