Tertiary winding
Tertiary winding
(OP)
What is the purpose of a tertiary winding on a transformer?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
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RE: Tertiary winding
Bill
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"Why not the best?"
Jimmy Carter
RE: Tertiary winding
Regards
Marmite
RE: Tertiary winding
robertplant
In Germany a tertiary winding is called "Ausgleichswickung". This can be translated to "compensation winding" or "equalizer winding", which very well explains the purpose of such a winding. A tertiary winding is a winding which usually is an internal winding, not transmitting power to the outside. Tertiary windings are always of the delta type, in most cases designed for only 6 kV. The purpose of a tertiary winding is to maintain a perfect Ampere-turn balance on all three core legs of a wye/wye transformer, regardless of the star point load. The majority of the HV grid coupling transformers are of the wye/wye type as a HV delta winding is very expensive because of the extra insulation required (a delta winding has 73% more turns than a wye winding, the copper weight is about the same). Wye/wye transformers with a tertiary winding are permitted to carry a full load star point current. Without a tertiary winding some standards are limiting the star point load current to 10%, or less, in order to avoid excessive voltage unsymmetry.
You may also look into threads 242-114285 and 238-125717 for additional information.
Regards
Wolf
www.hydropower-consult.com
RE: Tertiary winding
RE: Tertiary winding
RE: Tertiary winding
Thanks for your comment.
If the transformer purchaser wants a third (active) winding for station services, he gets it, of course. In such case he can specify any voltage. A third winding used for station services, for instance, has its specific purpose. This is obvious and I believe that Roberts question didn't go this direction. I assumed that he wanted to know what a "hidden", i.e. not power transmitting third (tertiary) winding, is for. This I tried to explain.
The transformer designer tries to keep the voltage of a compensation (tertiary) winding low for economical reasons. Still, you are right by questioning my 6 kV figure, which I herewith withdraw. The design voltage of a compensation (tertiary) winding can be as high as 30 kV, and even higher, depending on the transformer output and voltage. A 6 kV figure may be reasonable for, lets say, a 20 MVA/110 kV transformer.
Regards
Wolf
www.hydropower-consult.com
RE: Tertiary winding
JIM