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Kanka1-Visitor
1-Visitor
August 28, 2018
Question

Laplace transform problem. Does not get invlaplace transform.

  • August 28, 2018
  • 10 replies
  • 5284 views

Hello!

I have started to use Mathcad a bit for circuit analysis with laplace transform. However, often the invlaplace does not give the output i expect.

Am i doing something wrong?

 

I have attached a worksheet where i want to plot iL(t). However cant get it to work.

 

If i redefine the step function i am using (only using simple step) it works...... i need to be able to analyze step functions...

 

Would be great to get some input...

 

Best regards Kanka

10 replies

W
Werner_E25-Diamond I
25-Diamond I
August 28, 2018
@Kanka wrote:

Hello!

I have started to use Mathcad a bit for circuit analysis with laplace transform. However, often the invlaplace does not give the output i expect.

Am i doing something wrong?


No, Prime is doing wrong. It should work, but the symbolics (=muPad) in Mathcad is sure not state of the art and comparable with Maple or Mathematica 😞

Whenever you use a decimal point in conjunction with symbolics, the symbolics switches in some sort of numerics mode and calculations like equations solving or invlaplace might fail because of this.

I fear that there is not much you can do other than avoiding float numbers:

B.png

ttokoro
ttokoro21-Topaz I
21-Topaz I
August 28, 2018

RL circuitRL circuit

t.t.
W
Werner_E25-Diamond I
25-Diamond I
August 28, 2018

??

Yes, thats the same outcome as in the OPs sheet. I had not changed the plot limits he had set

B.png

 

    -
    -MFra-21-Topaz II
    21-Topaz II
    August 29, 2018

    ...So it's more beautiful .....

    kanka.jpg

    -
    -MFra-21-Topaz II
    21-Topaz II
    August 29, 2018

    The following errors of Prime and mathcad 15 have been known for a long time:

    errors.jpg

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