pspice help

Discussion in 'The Projects Forum' started by KingD, Mar 10, 2014.

  1. KingD

    Thread Starter New Member

    Mar 7, 2014
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    Okay so i have this circuit i am having trouble with, and no i am not building this
    I am using a 34,500 AC voltage source that is stepped down to about 6000 VAC and rectified to a DC voltage source so it can charge up a large amount of capacitors.

    Why am i getting negative numbers for voltage and amps?
    that does not make any sense to me

    Also, to get the voltage from 34.5k to 6k, how do i set up the transformer induction to do so?

    Need this asap, i appreciate any sort of help.
    I have taken 1 class for pspice, but it was only the basics.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,001
    3,229
    Those aren't negative numbers, they are very small positive numbers (meaning there is essentially nothing coming from the transformer secondary). Don't you understand scientific notation for numbers?

    Not familiar enough with P-spice to know how transformers are characterized. Doesn't the program have a help file?
     
  3. KingD

    Thread Starter New Member

    Mar 7, 2014
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    oh wow, my apologies, that is what i meant to say. I do understand scientific notation.

    They are very small positive numbers, but that still does not make any sense to me.

    It does, and i am actually going through it right now.
     
  4. tshuck

    Well-Known Member

    Oct 18, 2012
    3,531
    675
    I don't think you have used a transformer. I'm pretty sure you just used regular inductors.
     
  5. KingD

    Thread Starter New Member

    Mar 7, 2014
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    i did use a tranformer. In the Pspice part library, its called XFRM_LINEAR
    from the class i took, we used this one.
     
  6. KingD

    Thread Starter New Member

    Mar 7, 2014
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    0
    Also, no matter what value i change the AC voltage source to, the numbers that you see on the attachment, just stays the same.
    Same with changing the inductance values on the transformer, the numbers stay the same.

    I am not sure whats wrong.
     
  7. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    5,791
    1,103
    R1, R4 and the transformer have no values assigned/marked. How can pspice make sense of that?
     
  8. KingD

    Thread Starter New Member

    Mar 7, 2014
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    Oh didn't notice that, sorry once again.

    But they do have values, i just checked
    R1 and R4 both have values of 1k ohms

    and the transformer value i just guessed on and put a random value just to see if it works. L1 500 uH, L2 100 uH

    everything has values, but thank you for pointing that out
     
  9. crutschow

    Expert

    Mar 14, 2008
    13,001
    3,229
    What is the input frequency? For power line frequencies you need transformer inductances in the henry region, not microhenry. You need to look at some real transformers to get some representative values. Guessing at values seldom gives good results in circuit design or simulation. :rolleyes:
     
  10. LvW

    Active Member

    Jun 13, 2013
    674
    100
    KingD, all the displayed values are dc only, which result from the calculation of the quiescent operating point (calculated prior to ac simulation). Since there is no dc source in your circuit all values must be zero (practically, e-27 is zero).
    To verify the working of the circuit you must start a TRAN analysis (not ac, because ac is a linear small signal analysis only).

    EDIT: Don`t forget to use an appropriate voltage source Vsin (NOT Vac).
     
    Last edited: Mar 11, 2014
  11. KingD

    Thread Starter New Member

    Mar 7, 2014
    8
    0
    ohhh that makes more sense. thank you

    On the Vsin part, what is the difference between VOFF, VAMPL, AC
    i have to input something for each one, but not really sure what.
    i know the voltage source should be 34500V but not sure if that is VOFF, VAMPL, or AC
     
  12. LvW

    Active Member

    Jun 13, 2013
    674
    100
    * Voff is a dc voltage. As a result, the specified sinus voltage is riding upon this Voff value. For a pure sinus wave Voff=0.
    * Vampl is the amplitude of the input sinusoidal wave.
    * AC is for ac analyses only. That means: This input source can be used for TRAN or AC analyses.
    For TRAN: AC has no effect; for AC: Vampl has no effect.
     
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