Series RLC Circuit

  • Thread starter XuFyaN
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  • #1
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I have design this circuit from the book on the software "Electronic Work Bench" but see the 1st peak voltage in the attached image,

why it is in Giga Volts ???
the 1% of 1st peak voltage should be equal to the last peak voltage but this condition is not fulfilling here ...why ?

i have design another circuit and it is completely fine and i verified the first and last peak voltage and it is correct...buyt in this circuit why it is in Gvolts ?
 

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  • #2
berkeman
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I have design this circuit from the book on the software "Electronic Work Bench" but see the 1st peak voltage in the attached image,

why it is in Giga Volts ???
the 1% of 1st peak voltage should be equal to the last peak voltage but this condition is not fulfilling here ...why ?

i have design another circuit and it is completely fine and i verified the first and last peak voltage and it is correct...buyt in this circuit why it is in Gvolts ?
Looks like you are open-circuiting the current source? That would rail out the voltage, I would think. It would be nice if it gave you an error message for that, though.
 
  • #3
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yes but why the voltage is in GigaVolts ?? it should be 0 ?? and it is under damping circuit
 
  • #4
berkeman
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yes but why the voltage is in GigaVolts ?? it should be 0 ?? and it is under damping circuit
The output voltage of an open-circuited ideal current source is undefined. The GV value is probably just where it tops out at in the simulator. Much like the short-circuit current of an ideal voltage source, right?
 
  • #5
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yes but why the voltage is in GigaVolts ?? it should be 0 ?? and it is under damping circuit
Welcome to the reality of simulation.

Simulators lie because they are still only approximations of reality and not reality itself.

For the ideal circuit used in the simulator, this answer is probably exactly correct. Just as if you use a differential equation form of the circuit you'll get infinities in impulse and step responses!

But it's not a correct answer for the real world because of the approximation/idealization of the circuit model used the simulator to represent the real world circuit are just that: representations (aka approximations).

All simulators of any type have this problem which why anyone who blindly trusts what a simulator tells them is simply a fool/idiot.

This also why mastering hand-calculations of circuit analysis is still just as absolutely essential today as it was in the days of slide rules and paper calculation. You have to understand the real circuit well enough to recognize when the simulator lying to you.

Your case here is only an unusually obvious case of that mismatch between simulation and reality. Usually it's much more subtle. Knowing about step and impulse responses, you would expect these kinds of high voltages to occur in an idealized analysis.

So the reality is that capacitors do have some leakage (parallel R with every C) and inductors do have resistive losses (series R with every L) and switches do not turn on and off instantaneous and do have series resistance/inductance when closed and parallel capacitance when open. If you change your circuit to incorporate these kinds of 1st, then 2nd, etc. order parasitics, you'll start to get more "realistic" results.

But you'll have a whole lot more parameters to worry about. Welcome to engineering. You either have to trade this or "know" what to ignore from what the simulator is telling you.
 
  • #6
sophiecentaur
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Simulator operators should require special licences before they are allowed at them. Without a bit of on-paper analysis, first, they are as dangerous as chain saws.

You could reduce the risk of silly results if every Capacitor you use, initially, has a (large) resistor across it and every inductor has a (small) resistor in series. But then What Is Small or Large? Ahh, that's the question.
 

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