Please take a minute to review and accept our Terms of Use.
Welcome to the PLECS User Forum, where you can ask questions and receive answers from other members of the community.

Many technical questions regarding PLECS are answered on the Technical Solutions page of our website. Tutorial videos, specific application examples, and pre-recorded webinars are available on our YouTube page. Please follow us on LinkedIn for the latest Plexim news.

Can't create a s+1 transfer function

0 votes
51 views
I am having trouble creating a s+1 transfer function to represent the impedance of an inductor. Can't use the 1/(s+1) transfer function in the library because the order of the denominator must be greater than or equal to the order of the numerator. If I create the inverse function using the library transfer function block and then invert it I get a divide by zero error. I can solve that by using the saturation library block with the lower limit set to something just greater than zero. Then I try to invert it using the divide by library block nothing happens to the function - it does not get inverted. This seems like it should be so simple. Any suggestions?
asked May 13 by gkaminski (12 points)

1 Answer

+1 vote

The reason why this is not supported relates to the "Why is there no Derivative block in the component library?" question asked previously. 

One workaround would be to add a high-frequency cutoff for the impedance, much as would result in a practical inductor due to parasitic capacitances. The transfer function will be inductive at low frequencies and at higher frequencies the effects of the parasitic capacitances will dominate.  Most models should have the order of the denominator greater than that of the numerator.

A more general question is what is the goal of computing the impedance separately, opposed from using the impedance to compute a current value?

answered May 14 by Bryan Lieblick (745 points)
...