Phase Connection Interchanged in 3 Phase Transformers
Phase Connection Interchanged in 3 Phase Transformers
(OP)
I have a Dyn11 3 phase, Negative Polarity, wye-delta transformer connected to a supply with ABC phase sequence. One of my engineers informed me that the same transformer can be easily converted to Dyn5 by simply interchanging the H1 and H2 (phase A and B). He showed me a vector sketch of the Dyn11 and a Vector sketch of a Dyn5 and seems to be the same connection on both primary and secondary if he interchange H1 and H2 of the Dyn11 XFR. I also made a sketch myself and by interchanging the phases, rotated the primary delta vector to point the "new phase A" at top reference and if I convert to wye, I found out that the phase sequence on the wye side is reversed to CBA.
Is my vector sketch correct or his? I am also assuming to relate the same case to an induction motor with delta connected winding that if I interchange the 2 phases, I get reverse rotation due to reversed phase sequence.
Is my vector sketch correct or his? I am also assuming to relate the same case to an induction motor with delta connected winding that if I interchange the 2 phases, I get reverse rotation due to reversed phase sequence.
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RE: Phase Connection Interchanged in 3 Phase Transformers
RE: Phase Connection Interchanged in 3 Phase Transformers
My engineer is refering on swapping phase terminals without opening the transformer. Swapping the primary cable connections that is. Do you mean I can derive Dyn5 from a Dyn transformer by simply swapping cable terminations on both primary and secondary terminals? What cable phase I will interchange on both primary and secondary then? If you can provide me then I will try to re-check the vector skectch myself. Your assistance is highly appreciated.
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RE: Phase Connection Interchanged in 3 Phase Transformers
Yes, you need only swapp cable termination on both of sides.
See 3 options for swapp:
HV LV
L1 L2 L3 L1 L2 L3
1U 1W 1V 2W1 2V1 2U1
or
1W 1V 1U 2V1 2U1 2W1
or
1V 1U 1W 2U1 2W1 2V1
L1, L2, L3 in ANSI A,B,C : connection to conductors.
Regards.
Slava
RE: Phase Connection Interchanged in 3 Phase Transformers
RE: Phase Connection Interchanged in 3 Phase Transformers
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RE: Phase Connection Interchanged in 3 Phase Transformers
Thank you.
According to you FAQ, my post is wrong or I'm not underastand something.
I know 100%, this type of connection work correctly.
Please correct me.
Regards.
Slava
RE: Phase Connection Interchanged in 3 Phase Transformers
The best way to see it is to draw a vector-diagram of any star/delta or delta/star transformer.
Now, on that chosen transformer, change the transformer connections just on one side. By rotating the connections, the vectorgroup is also changing. Thus, by using a Dyn1 connection, rotation on one side will result in either a Dyn5 or a Dyn9 transformer. By rotating the phases, you will not change phase sequence. (for a Dyn11-connection it will result in either a Dyn3 or a Dyn7-connection)
If you put the vector-diagram of a Dyn1 next to a Dyn11, you'll notice that the two is mirror images of each other. Thus, by changing the phase rotation (swapping two phases) on both sides, (From ABC to ACB and abc to acb) you'll change the vector group from a Dyn1 to a Dyn11.
Unfortunately it is difficult to explain without drawings. By checking your first post, it seems as if you haven't change your vector-group at all, the shift between primary and secondary stays the same with every rotation.
nightfox1925:
By changing just on one side of the transformer, you are not going to change a Dyn11 transformer into a Dyn5-connection. The Dyn11 transformer will change either to a Dyn7 or a Dyn3 by changing connections on one side only. To change from a Dyn11 to a Dyn5, you'll have to change connections on both sides of the transformer.
Just a note:
Although it seems to be not important, remember that Dy is actually Delta-wye and not Wye-delta.
What do you mean by negative polarity?
Remember, a transformer is internally wired to be a certain vector-group. We can change the vector-group by doing unconventional connections external, but internal the transformer remains the same. Thus a Dy11 transformer is wired internally to be a Dy11, and it will stay a Dy11 without any internal changes, but we can change the system (unconventional) such that the transformer behave like either a Dy1, Dy3, Dy5, dy7, Dy9 or Dy11 transformer.
Regards
Ralph
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RE: Phase Connection Interchanged in 3 Phase Transformers
I'm agree with all your words.
I write my first e-mail after diagrams.
Please see again, in each case I change both of connection
(LV and HV). Now I check again myself, I see it's OK.
Thank you.
Slava
RE: Phase Connection Interchanged in 3 Phase Transformers
Ohhh, I drw vector groups with several options.
Any problem.( some my black-out).
We told about same.
Thank you.
Slava
RE: Phase Connection Interchanged in 3 Phase Transformers
I will draw the vector diagram with your tips in mind and see the result. I will provide you the details on my next post and attach the scanned sketch.
Thanks for the support.
GO PLACIDLY, AMIDST THE NOISE AND HASTE-Desiderata
RE: Phase Connection Interchanged in 3 Phase Transformers