Delta Transformer
Delta Transformer
(OP)
Can someone explain why on a 3 phase delta transformer (460/208) on the load side that 1 of the phases if you check it to ground does not show 208V but the other 2 phases do. But if you take off the load you get 208 to ground and if you check phase to phase it shows 208v. I was told it was refered to as a "freak leg". Could someone please explain this.





RE: Delta Transformer
1. Your data does not make sense. As it does not fit any standard "delta" or "wye" system in the USA.
2. Post the nameplate data of the transformer in question. It appears that you have not personnaly taken the readings or have not noted them correctly.
3. Use help of your electrical group, and verify how, if at all, the secondary of the transformer is grounded.
4. Look up a copy of NEC Handbook, articles 230 and 250 that one of your electrical collegue will have. All common tranformer configurations are explained in there. See which one of them fits your system readings.
RE: Delta Transformer
A.
RE: Delta Transformer
Try a Google search on "wild leg delta".
RE: Delta Transformer
RE: Delta Transformer
RE: Delta Transformer
RE: Delta Transformer
Also, the transformer is not grounded.
Also, 208 volts to ground on all three phases does not make sense.
You have at least two serious problems and possibly more.
1> Grounded load.
2> Ungrounded transformer.
3> The readings of 208 volts to ground on all three phases are probably not correct. If they are correct or even significantly different from the 120 volts that they should be, you may have a high resistance connection at the common wye and ground connection and possibly an interaction with the 460 volts. (Is this an autotransformer?)
I suspect that your transformer is 460V(or 480V)delta to 120/208V wye.
Just calling an electrician may not be enough. There are many industrial electricians that are familiar with these systems and are able to competently trouble shoot them.
There are many residential electricians who would be lost on this system. There are many more electricians in between.
BE AWARE THAT YOU MAY HAVE LETHAL VOLTAGES ON CIRCUITS OR WIRES THAT ARE NORMALLY AT GROUND POTENTIAL.
respectfully
RE: Delta Transformer
If you can completely remove the supply form the refer unit try checking from a known ground to each lead. See if one is common with the ground.
Again BE CAREFUL.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com