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-   -   DC short circuit calculation. (https://www.askmehelpdesk.com/showthread.php?t=142767)

  • Oct 20, 2007, 03:21 AM
    danar
    DC short circuit calculation.
    Any one familiar with DC short circuit calculation?
  • Oct 21, 2007, 05:21 AM
    tkrussell
    What do you mean "familiar"?

    Sure, I am familiar.

    What is your specific question?

    Will this help?
    Calculation of short circuit currents

    The answers you receive would be better if you were not so cryptic with your questions.

    I thought "engineers" tend to be more detailed and specific. Add more detail than just one sentence broad questions.
  • Nov 7, 2007, 04:33 AM
    danar
    What I mean is DC short circuit current calculation.. we use to do AC short circuit current calculation but for DC I think it has different parameters...
  • Jul 28, 2008, 12:35 AM
    SuryaGG
    tkrussell,

    I am also looking for the answer to danar. The link in your reply does not discuss anything about DC (power system) short circuit current calculation.
  • Nov 8, 2008, 01:12 AM
    danar
    Quote:

    Originally Posted by SuryaGG View Post
    tkrussell,

    I am also looking for the answer to danar. The link in your reply does not discuss anything about DC (power system) short circuit current calculation.


    Hey guys the question above still stands!! Any suggestions??
  • Nov 8, 2008, 04:23 AM
    tkrussell
    Try this:

    direct current DC arc

    And this:

    http://www.msha.gov/S&HINFO/TECHRPT/...L/INSTAN30.pdf
  • Sep 22, 2011, 05:35 AM
    rifky
    1 Attachment(s)
    Guys, this might help.
    DC current increase can be analysed using exponetial method. Please see the graph in the attachment as well

    If a fault-short circuit develops, the current in the circuit increases exponentially, as shown in the Graph A. Mathematically, the current increase in the circuit can be written down by the following equation:
    I=IA • (1-e-(L/R)t)
    The value of available current IA, normally called expected current IP, is determined by the Ohms Law IA=U/R , but the value L/R= Τ is a time constant. The upper equation shows the L/R constant impact on the fusing time, where
    di/dt = U/L = IA / Τ
    Therefore, the higher the time constant L/R the lower the discharge di/dt and the longer the fusing phase.
    Graph B shows that due to lower inductance, current increases faster and the fusing time is shorter in comparison with the conditions in the Graph C, where an example of current increase at high time constant is presented.

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