Delta-Y Connected Load Transformation

  • Thread starter Jinium
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Homework Statement


yd69Ylv.png

Based on Fig. 4,
ZΔ=6+8j Ω
ZY=4+3j Ω
EL=200V

Show that the equivalent delta-connected load is 7.846 - 2.77j

Homework Equations


ZY=(1/3)ZΔ

The Attempt at a Solution


Here's my thought process:
For part (i), attempt to convert Y to Δ,
So using the relevant equation above
ZΔ of transformed ZY is 12 + 9i
However, that's not done because I need to combine the two delta loads.
Hence, I use the product/sum rule to obtain the combined delta:
((12+9i)(6+8j))/((12+9i)+(6+8j))
which obtained 4.1598 + 4.405j which is wrong

I also used https://www.physicsforums.com/threads/delta-and-star-transformation-ac-circuits.791979/ as guidance for this problem but can't quite point out where my mistake is.
 

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  • #2
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The existing impedance of the delta portion is 6 - j8. You used 6 + j8.

Try that.
 
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  • #3
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The existing impedance of the delta portion is 6 - j8. You used 6 + j8.

Try that.
Worked ! Guess I haven't studied enough. I should go read up on the positive and negative conventions of these circuits. I was not aware it could be a negative just from the diagram.

Thanks, magoo !

EDIT: Got it. It's negative on 8j because it's a capacitor. It would be positive if it were and inductor instead.
 
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