This is a spinoff of the thread found here: https://electronics.stackexchange.com/questions/115510/proteus-8-error-timestamp-too-small

I have found that a lot of the problems I have been running into were due to the feedback transformer coils not being grounded. I wanted to ask why in the world a simulation software would require that each of the coils on a transformer be grounded, when in real life that is not always the case? It makes no sense to me.

My question is how might I get around this, if it's possible at all? My circuit places the primary inside a circuit, and neither side can be grounded.


The above is the circuit I am using, and the transformer in question is the one labeled "FEEDBACK_XFMR".

  • \$\begingroup\$ I don't know the answer to your specific question, but in the past when I have had issues in some simulators with transformers I have replaced the transformer with coupled inductors (with coupling coefficient sized to give appropriate leakage inductance) and have had better success. You might give that a try. \$\endgroup\$
    – John D
    Commented Jun 17, 2014 at 23:19
  • \$\begingroup\$ Good thought. Unfortunately I don't know how to couple inductors in proteus, but I will look into it. Many thanks \$\endgroup\$
    – DerStrom8
    Commented Jun 17, 2014 at 23:25
  • \$\begingroup\$ Hmm, not finding much documentation on mutually-coupled inductors in Proteus.... \$\endgroup\$
    – DerStrom8
    Commented Jun 17, 2014 at 23:40

1 Answer 1


All SPICE-based simulators are like this- they need a reference voltage (usually node 0, "Ground").

Anyway, the solution is simple- just put some high value resistors (something like 1G ohm) to ground on the parts that are "floating" wrt 0V.

  • \$\begingroup\$ Ah, great idea! I can't believe I never thought of that! Well it solves this issue, but I'm still having trouble with nodes that can't be found when I click on it in the messages window. The issue is more clearly explained in my original post that I linked to earlier. For the time being though, I think this is the answer to the above question, so many thanks! \$\endgroup\$
    – DerStrom8
    Commented Jun 18, 2014 at 14:36

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