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Topic Title: Delta Configuration of Transformer
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Created On: 12 November 2013 04:59 PM
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 12 November 2013 04:59 PM
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Joined: 26 October 2013

I have a few confusions related to the delta configuration of a transformer (single-phase transformers used to make a 3-phase transformer):

1) In a closed delta, the windings are connected such that H2 end of one winding is connected to H1 of the other winding. What will happen if one of the windings is reversed?
The flux in that winding should be opposite and thus the induced emf should also have opposite polarity..but that isn't possible! because induced emf should be equal to voltage applied across the winding. Also, what would be the effect of one reversed winding on the other windings?

2) I've been thinking (and searching) about this for days but haven't reached anywhere:
How do you calculate the total power output of an open delta transformer? I don't understand the explanation given in various texts and on websites that calculate power using the sqrt(3) EI formula (where I is line current).

The sqrt(3) EI formula was for closed delta because in a closed delta, we calculate the power delivered by one winding as E*Iphase which becomes E*(I/sqrt(3)) since phase current=I/sqrt(3), and then multiply by three.
But why are we using this formula for open delta?
And btw, in the conductor attached to the point where the two windings are joined together, would the line current be sqrt(3)*Iphase?

Edited: 13 November 2013 at 03:27 PM by QwertyXP
 12 November 2013 06:07 PM
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Might I suggest an excellent piece of open source software called QUCS?

You can set up the circuits as you describe and monitor the output; then you can switch connections about to see what happens to the output. It's a good way to visualise what is going on.
 13 November 2013 10:13 PM
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Three single phase transformers are different to a three phase because the windings are linked by the magnetic circuits in the three phase case. The same linkage is not present when three single phase units are used. Your open delta must refer to the secondary side as otherwise you aren't energising all the primary coils. If you model it you need to be sure to include these. This means that the effects of reversing a winding will be different!

Edited: 13 November 2013 at 10:21 PM by statter

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