
#1
May1111, 01:07 PM

P: 13

please i need your help to answer the following question
what the difference between transformer Dyn11 and Dyn1 i know the difference is in leading and lagging of line to line voltages of primary and secondary but the question is , when i should use Dyn11 or Dyn1 as a must in the network does it depends on the type of load ? all what i know that in parallel operation the 2 transformers must be exactly the same , but what according to what in the first place we choose Dyn1 or Dyn11 anybody have an idea ??? 



#2
May1111, 06:14 PM

PF Gold
P: 322

Dy11 signifies a Delta Primary (primary has an upper case letter), Wye secondary (secondary has a lower case letter) and the orientation of the 3 phase diagram, relative to the A phase on a clock face pointing to 11 o'clock. So draw 3 vectors 120 degrees apart to represent the 3 phases, but start with your reference phase (A phase) at 11 o'clock. Dy1 would hence be a Delta primary, Wye secondary and a vector diagram with the reference vector pointing at 1 o'clock. I believe most 3 phase textbooks have the vector diagram with the reference vector at 0 degrees on the xaxis, which would equate to 3 o'clock, then with B at 11 o'clock and C at 7 o'clock. And yes, if you want to parallel transformers they have to be of the same vector group or you will have circulating currents and associated problems. 


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