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Anselme1-Visitor
1-Visitor
October 2, 2018
Solved

Getting started with Laplace in MathCAD

  • October 2, 2018
  • 4 replies
  • 11006 views

I am trying to get started with Laplace transform in MathCAD 15 and I would like help to find what I did wrong in the document I uploaded.

It’s a simple second order RC circuit. V1 is a constant value. I tried to find V2(t). C2V0 and C1V0 are initial conditions of capacitors.

 

The result I got with invlaplace makes no sense.

Thanks

This topic has been closed for replies.
Best answer by -MFra-

I have to make a small correction:

For Anselme 12.jpg

You can do even so:

For Anselme 123.jpg

4 replies

L
LucMeekes23-Emerald IV
23-Emerald IV
October 2, 2018

Does this help:

LM_20181002_Laplace.png

(Note that the last expression runs further to the right. See attached Mathcad sheet.)

 

Success!

Luc

    A
    Anselme1-VisitorAuthor
    1-Visitor
    October 2, 2018

    Thanks Luc,

     

    But your sheet doesn't run in my MathCAD 15. see attached jpg

     

    L
    LucMeekes23-Emerald IV
    23-Emerald IV
    October 2, 2018

    Funny, it would mean that your Mathcad cannot even solve the first set of equations (no Laplace involved there). That's unbelievable.

    I generally have Automatic Calculation switched off. Did you press F9 after opening the sheet...?

     

    Success!
    Luc

      -
      -MFra-21-Topaz II
      21-Topaz II
      October 2, 2018

      Hi Anselme,

      Allow me to point out you that the circuit you have drawn as  the Laplace transform of the given network, however, contains an error. In fact the Laplace transform of a constant voltage L(V1) = V1/s, instead you wrote V1 which is the Laplace transform of a Dirac pulse of area V1. So if the voltage source is an independent and constant voltage generator,  you have to correct the drawing and all the calculations.

      Greetings

        A
        Anselme1-VisitorAuthor
        1-Visitor
        October 2, 2018

        Hi Luc,

        I was hesitant about that.

        If I use V1/s, MathCAD dont solve the invlaplace at all.

        see attached

        V
        24-Ruby III
        VladimirN24-Ruby III
        24-Ruby III
        October 2, 2018

        Here is a result from Mathcad 15 M045.

        -
        -MFra-21-Topaz II
        21-Topaz II
        October 2, 2018

        Hi Anselme,

        my solution without R1:

        For Anselme.jpg

          A
          Anselme1-VisitorAuthor
          1-Visitor
          October 2, 2018

          Can you attach the worksheet?

          -
          -MFra-21-Topaz II
          21-Topaz II
          October 2, 2018

          Hi Anselme,

          my solution is the followinig:

          For Anselme 11.jpg

          -
          -MFra-21-Topaz IIAnswer
          21-Topaz II
          October 3, 2018

          I have to make a small correction:

          For Anselme 12.jpg

          You can do even so:

          For Anselme 123.jpg

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