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I am experiencing difficulties with a question:

A balanced three-phase load shown in the diagram is connected across a 380V, 50 Hz three-phase supply, ABC phase sequence. The voltage VAB is taken as reference.

WYE Circuit



Part of the question I am trying to answer includes converting the WYE circuit to a Delta circuit as I have done:

Delta Converted Circuit


Now, my main question is how do I work out the phase angle of each component?
My textbook does not have notes on how to determine the phase angle. All they say is VBC is generally used as the reference phasor. But in this case, VAB is used as the reference phasor and I don't know how to determine the angles for the phasor diagram. I thought of rotating the reference diagram of VBC so that VAB = 0, VAC = 120 and VBC = 240. Would I be correct on this approach? Please advise

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  • \$\begingroup\$ can you please help me with my question? electronics.stackexchange.com/questions/161942/… its hard getting power system answers here, everyone talks electronics \$\endgroup\$ – Electron Mar 27 '15 at 19:16
  • \$\begingroup\$ @user2756746 - your question pictures are quite difficult to make out and it looks like you stopped half way thru - there is a "(" after the 1/3 and this doesn't instill confidence in the question. \$\endgroup\$ – Andy aka Mar 27 '15 at 19:28
  • \$\begingroup\$ @user2756746. I suggest you rewrite the question in HTML text (physically typing it out on your keyboard), diagrams and complex formulas should be in image format (neatly sketched) and lastly attempt the question fully to the best of your ability. The StackExchange policies are strict. \$\endgroup\$ – n0t_a_nUmb3R Mar 29 '15 at 19:24
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Now, my main question is how do I work out the phase angle of each component?

Draw a phasor diagram: -

enter image description here

In delta, the loads are connected across three line voltage namely Vab, Vbc and Vca. These are shown above on the diagram - they are 120 degrees apart. It's simpler because the three delta loads are all equal and mainly reactive (hence the angle close to 90 degrees). So, for each of the individual line voltages, the current will lag by 76 degrees.

Here's another diagram that is for a delta load of just resistors: -

enter image description here

Important to note is that Ia = Iab - Ica and this tells you how the individual load currents sum to give you the phase current.

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