ZIG ZAG TRANSFORMER
- Thread starter domnic
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junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
rotated phase/vector method of providing ground to delta system while maintaining capability to short circuit triplett harmonics.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
In general, when would one use a zig zag instead of a delta-wye?
Maybe, just maybe, you meant to say "wye-delta" grounding transformer?
electrofelon
Senior Member
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- Cherry Valley NY, Seattle, WA
I dont believe so.....If I wanted to make a grounded system out of an ungrounded system, I could use a 1:1 voltage ratio transformer with the ungrounded supply connect to the delta primary and the ground the wye secondary, no? I assume the reason to use a zig zag would be it is an autotransformer so it could be smaller and cheaper, however not sure how real world economics like common availability come into play...
Tony S
Senior Member
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- Resting under the Major Oak UK
They can be used where it is known the loading will out of balance. One disadvantage is they use 30% more copper in the secondary.
MD84
Senior Member
- Location
- Stow, Ohio, USA
Why not just use a wye delta and connect your ungrounded system only to the wye primary.
junkhound
Senior Member
- Location
- Renton, WA
- Occupation
- EE, power electronics specialty
If a ground is desired on a delta system to allow for line to ground faults to trip a breaker, zig zag can be used.
If the only reason is to provide a grounded system at a secondary, then the delta-wye works, but line ground primary faults do not trip.
If you say why not just use a wye to wye transformer, now the harmonics all go to the neutral causing a plethora of other problems (white wire turns brown, :weeping:etc). Remember, in a delta-wye, the triplett harmonics are all in phase in the primary thus are short circuited - which brings up the point that the delta windings need to be heavier copper to carry the short circuited harmonics. That impacts the economics of the overall situation also.
Interestingly, the only zig zag xfmrs I've ever seen actually installed at a service drop were at Minuteman LCFs. Had never heard of them prior to that (1970).
If the only reason is to provide a grounded system at a secondary, then the delta-wye works, but line ground primary faults do not trip.
If you say why not just use a wye to wye transformer, now the harmonics all go to the neutral causing a plethora of other problems (white wire turns brown, :weeping:etc). Remember, in a delta-wye, the triplett harmonics are all in phase in the primary thus are short circuited - which brings up the point that the delta windings need to be heavier copper to carry the short circuited harmonics. That impacts the economics of the overall situation also.
Interestingly, the only zig zag xfmrs I've ever seen actually installed at a service drop were at Minuteman LCFs. Had never heard of them prior to that (1970).
MD84
Senior Member
- Location
- Stow, Ohio, USA
I have seen on wye wye transformers a tertiary delta is used. Pesky harmonics...
Phil Corso
Senior Member
- Location
- Boca Raton, Fl, USA
Gentlepeople...
There's a world of difference between the Zig-Zag vs Delta-Wye used as a derived-grounding source for an ungrounded system. And, frankly, I always chose the former!
Phil Corso
There's a world of difference between the Zig-Zag vs Delta-Wye used as a derived-grounding source for an ungrounded system. And, frankly, I always chose the former!
Phil Corso
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I dont know, why not?
Ok I am a bit confused here. I think it depends on what exactly we are trying to accomplish. Say I have an ungrounded 480V (or whatever) service. I may want to create a neutral/ground reference for the SERVICE, OR I may not care a about a neutral for the service, but want one for downstream stuff. Using a delta-> wye only gets me that latter and I need a relatively large transformer. What is the comparison between the zig zag and using a wye->delta as an autotransformer?Well dont leave us in suspense, please elaborate!
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
My understanding is that there are _two_ uses of the term zig-zag. One is for an autotransformer used to derive a neutral on an ungrounded delta system.
The other use is as the secondary for a variant on the delta-wye isolation transformer that shifts the phase relationship between primary and secondary. This can be used for harmonic mitigation.
Again, two different uses are possible: the normal use of a delta -> wye transformer is as you describe, to provide a downstream grounded system. However delta-wye transformers can also be used as grounding transformers. In this use, the _wye_ is connected to the system to be grounded, and the delta is permitted to 'float'. Circulating currents on the delta perform the same function as the zig-zag: making the neutral low impedance.
-Jon
The other use is as the secondary for a variant on the delta-wye isolation transformer that shifts the phase relationship between primary and secondary. This can be used for harmonic mitigation.
Again, two different uses are possible: the normal use of a delta -> wye transformer is as you describe, to provide a downstream grounded system. However delta-wye transformers can also be used as grounding transformers. In this use, the _wye_ is connected to the system to be grounded, and the delta is permitted to 'float'. Circulating currents on the delta perform the same function as the zig-zag: making the neutral low impedance.
-Jon
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
how much is the phase shift? Clearly a delta-wye already shifts 30 degrees....
Tony S
Senior Member
- Location
- Resting under the Major Oak UK
0° or 60°
Tony S
Senior Member
- Location
- Resting under the Major Oak UK
I forgot to add 300°
It depends on how you zig or zag :roll:
It depends on how you zig or zag :roll:
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