Solving a Delta circuit.. Help?

Discussion in 'Homework Help' started by thekenman, Nov 22, 2012.

  1. thekenman

    Thread Starter New Member

    Nov 22, 2012
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    Hello I am new here and new to circuits in general. I just learned about the Delta to Wye conversion and have been struggling with some homework for the past couple hours :/

    [​IMG]

    I built this in multi-sim, and have done the conversion to a "Y" circuit in order to find the total current and an equivalent resistance for R3,4,5,6,7.

    Howver my teacher wants to see calculations for getting the Voltage drop and current through each resister in the original circuit, not the Y transform. I am having a lot of difficulty so some help woudl be appreciated.

    So Far I have worked out that R1 will have an 8.114V drop, with 24.58mA going through it. But after that I just keep getting stuck :/
    edit: I know I have all the numbers, I only used multi-sim to confirm the calculations that I thought would be so easy to get. Sorry about all the multi-meters. And ofcourse XMM8 and XMM9 are measuring current and have no effect on the circuit

    ALSO if it helps I know the total resistance is 976Ohms, and the Req of R3,4,5,6,7 is 546Ohms
     
    Last edited: Nov 22, 2012
  2. bonshie

    New Member

    Nov 21, 2012
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    0
    Hi,
    very nice circuit.
    You have mentioned that you got your VD(Voltage drop) already on the resistor,R1.
    Before I proceed to my explanation.Did you draw this circuit by yourself?
     
  3. thekenman

    Thread Starter New Member

    Nov 22, 2012
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    0
    I drew this circuit in a program called Multi-sim, but I did not design the circuit. It is part of a LAB in my circuit analysis class.

    The VD for R1 was very simple because it is in series with the power supply, since I already converted the delta to a wye I know the total resistance for the circuit is 976 Ohms. So I found the Total Current 24/976 = 24.59mA.

    Using that total current I just did .02459 x 330 = 8.114V for R1. I also found Voltage Drop of R2 using the same method.

    I have done some reading around about mesh analysis but I havn't learned this yet in class, and it seemed to complicate my problems further.

    From what I gather I am supposed to work backwards from my Wye conversion to get the currents? boggles my mind though
     
  4. thekenman

    Thread Starter New Member

    Nov 22, 2012
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    0
    Here is the equivalent circuit I made
    [​IMG]

    it can obviously be simplified way down, but I think I am supposed to solve my original circuit using this conversion somehow?
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,751
    4,799
    Worked it out... how?

    Okay. Stuck where? Stuck how? What have you tried? Are we supposed to use our psychic powers to figure this out?

    Please follow the posting guidelines for this forum and present your attempts to solve the problem so that we can see how you are trying to go about it, how far you are getting, and at what point you start going astray.

    How do you know either of these? Show your work.

    If you are able to figure these out, what is preventing you from find the currents in these resistors?

    Have you heard of node voltage or mesh current analysis? If not, have you heard of branch current or loop voltage analysis?
     
  6. thekenman

    Thread Starter New Member

    Nov 22, 2012
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    0
    @WBAhN

    I answered pretty much all of your questions in he post above yours.

    I am reading about branch current right now but have not been taught it. I derived the total resistance and that 500 something number from the equivalent circuit I made and posted also in the post above. I have not been taught any of the methods you listed so I don't believe my teacher is looking for those solutions
     
  7. The Electrician

    AAC Fanatic!

    Oct 9, 2007
    2,281
    326
    Using the same method you used to find the voltage across R1, you should be able to find the voltage across R3. You can then find the voltage at the bottom of R3. You know the voltage at the right end of R2.

    Knowing these two voltages gives you the voltage across the R4, R5, R6, R7 sub-network. Then you can find the currents through these 4 resistors individually, and the voltages across them.

    Now you know the voltages at the corners of the delta network R3, R4, R5 in the original network, and that gives you the voltages across those resistors, and thence the currents through them.
     
  8. WBahn

    Moderator

    Mar 31, 2012
    17,751
    4,799
    I don't see how you got your equivalent circuit. Again, please show some work.

    It seems odd that you are being expected to use delta-wye transforms and haven't been shown basic circuit analysis techniques.

    Have you at least been shown KVL and KCL?
     
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