The Unbalanced Delta

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Re: The Unbalanced Delta

I decided to go ahead and realign the "designators" in the setup diagram per convention.

Engy, based on the primary phasor diagram, the "phase sequence" of all three secondaries is the same a-b-c, but the "phase shift" is different.
 
Re: The Unbalanced Delta

OK, I made the PSPICE work, but it takes a lot of interpretation. It does show that the 2:1 current ratio is correct.

Now it seems that the first wye-delta config shows +/- 60 degrees phase shift in the lightly loaded transformers. The first transformer handles 2/3 of the real power with the other 1/3 divided equally between the other two.

Will check out the other configs next.
 
Re: The Unbalanced Delta

Be sure to review your primary currents too. Use a "phantom - wye," as I've shown in the once again revised digram, to describe the primary/secondary phase shift.

[ April 01, 2005, 10:06 AM: Message edited by: rbalex ]
 
Re: The Unbalanced Delta

OK Bob, no one else will step forward so here goes:

Assume all transformers to have a 1:1 turns ratio and label them A, B, & C.

All primary/secondary phase voltages equal.

Of course there is line to line voltage drop and phase shift in the wye-delta, but that is routine.

Load current, I, shared 2/3 in A, 1/3 in B & C in all three configurations.

Delta-delta:

Line current is ?I? in H1 & H2, zero in H3. In phase with Vphase in A, 60 degree lead/lag in B & C.

Wye-delta 1:

Zero neutral current.

Wye delta 2:

Same as previous case except that secondary phase sequence reversed.

All this from inspection except that I did simulate the load sharing to prove that 2:1 was right.
 
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