We've got a delta-wye combination of inductors.

So the delta part is connected to the/a 3-phase voltage source which delivers the voltage E across any combination of 2 phases.

So across the delta connection the voltage drop across each inductor is E.

Now it is claimed that the voltage drop across 2 of the inductors in the wye-connection is E * sqrt(3), in other words between any 2 phases in the wye connection.

Now I can't see the reasoning behind the last claim, how does one find that? And how exactly are the delta and wye connected togheter?

delta wye connection


You need to understand phasor diagrams and then do some basic trigonometry. Consider this: -

enter image description here

The blue lines represent the voltages across each delta coil in your question. Now if you rearranged to a Y connection, to get the same voltage across each coil you would have to increase the line voltage (Vca, Vab or Vbc) by \$\sqrt3\$ to maintain the voltage across each coil as the same when it was delta wired. It's just trigonometry.

  • \$\begingroup\$ I understand the trigonometry-approach now. But on all the diagrams I have seen the wye and delta are not attached togheter with cables. I'm wondering where the cables between the delta and the wye go, how are they connected to each other in other words or are they not physically connected anywhere? \$\endgroup\$ Oct 28 '16 at 19:54
  • \$\begingroup\$ Sorry dude but I don't follow you. \$\endgroup\$
    – Andy aka
    Oct 28 '16 at 20:30
  • \$\begingroup\$ ok in the picture i posted on top here, there is a picture of a wye and a delta. When we say delta-wye connection, I assume the delta is connected to the wye. So in other words, the cables going from delta where do they join the cables coming from the wye. In short words, how is the connection setup (cables go from where to where) connecting delta with the wye? \$\endgroup\$ Oct 28 '16 at 20:36
  • \$\begingroup\$ A transformer, motor or generator, for example can be re-wired to turn it from Y to Delta to suit the incoming voltage - is this the sort of thing that you mean? \$\endgroup\$
    – Andy aka
    Oct 28 '16 at 20:38
  • \$\begingroup\$ A transformer yes, but as i understand it the delta-wye exist in the same transformer at the same point in time and achieving a voltage increase at the wye side. So i guess the primary would be delta and secondary wye. \$\endgroup\$ Oct 28 '16 at 20:44

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