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Simulation of the behaviour of a PCB spark gap
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Marco:
U=I*R ... the ESD test is fundamentally voltage driven. If you try to make a current driven test you will force the voltage to unrealistic values the moment the gap differs slightly from what the current waveform was measured for. It will have fuck all to do with IEC-61000-4-2 and it will have no practical value.

I doubt you will find any simulation software of useful predictive value, even if you give up on trying to force a current waveform.
T3sl4co1l:

--- Quote from: Marco on August 03, 2018, 10:49:06 am ---U=I*R ... the ESD test is fundamentally voltage driven. If you try to make a current driven test you will force the voltage to unrealistic values the moment the gap differs slightly from what the current waveform was measured for. It will have fuck all to do with IEC-61000-4-2 and it will have no practical value.

I doubt you will find any simulation software of useful predictive value, even if you give up on trying to force a current waveform.

--- End quote ---

The standard describes a system of several meters in length; the risetime of the spark itself is small compared to this length scale.  Consequently, the transient is a propagating wavefront, with well defined impedance: that of the grounding cable, circuit traces and so on.

The schematic typically given (a capacitor, resistor and switch), is at best, a caricature of the real system.  It might be a description of the components involved, but it is not a model of the system!  That would require an RLC equivalent to the published waveform.  At least a two stage RLC network, equivalent to the sub ~300MHz response of this transmission line system.

Tim
marc1996:

--- Quote from: T3sl4co1l on August 04, 2018, 10:53:27 am ---
--- Quote from: Marco on August 03, 2018, 10:49:06 am ---U=I*R ... the ESD test is fundamentally voltage driven. If you try to make a current driven test you will force the voltage to unrealistic values the moment the gap differs slightly from what the current waveform was measured for. It will have fuck all to do with IEC-61000-4-2 and it will have no practical value.

I doubt you will find any simulation software of useful predictive value, even if you give up on trying to force a current waveform.

--- End quote ---

The standard describes a system of several meters in length; the risetime of the spark itself is small compared to this length scale.  Consequently, the transient is a propagating wavefront, with well defined impedance: that of the grounding cable, circuit traces and so on.

The schematic typically given (a capacitor, resistor and switch), is at best, a caricature of the real system.  It might be a description of the components involved, but it is not a model of the system!  That would require an RLC equivalent to the published waveform.  At least a two stage RLC network, equivalent to the sub ~300MHz response of this transmission line system.

Tim

--- End quote ---


--- Quote from: 3roomlab on August 03, 2018, 11:35:47 am ---not sure the exactness of parameters, but a neon lamp seem able to wing it?
checkout the "small" current gg thru the 2 "resistors". there is a HV charge in cshunt parameter
V2 flushed down the "neon" somewhat? "randomly" at 4000A "spark" peak?
if somebody have a better idea about the parameters, pls repost corrections

--- End quote ---


--- Quote from: Marco on August 03, 2018, 10:49:06 am ---U=I*R ... the ESD test is fundamentally voltage driven. If you try to make a current driven test you will force the voltage to unrealistic values the moment the gap differs slightly from what the current waveform was measured for. It will have fuck all to do with IEC-61000-4-2 and it will have no practical value.

I doubt you will find any simulation software of useful predictive value, even if you give up on trying to force a current waveform.

--- End quote ---

Sorry for my delay responding you guys.

I think that my answer can respond to you 3 at the same time.
Using LTSpice that's the circuit that I actually have(attached picture). Everything inside the box is what simulates the waveform of the supposed ESD. This is an equivalent circuit that I found in internet. The simulation is really accurate acording to the supposed waveform. The problem is that varying the distance of the voltage breakdown doesnt change nothing apart from moving the supposed current in the time domain, I mean, when i change the parameter "d", if the peak starts at 5 ns then it will be at 10, but the value is really the same

I don't know if I have to change some parameters of the gap values apart of the breakdown voltage because I do not know at all what they mean.
If someone is more experienced in this software and could help me please let me know.

Also, one member from another forum said me that if I finally get with LTSpice to simulate what I really want, changing the distance value between the electrodes I could simulate an spark gap as an array of micro-spark gap, and I think that is something that could be really interesting.

T3sl4co1l:
You won't observe anything different because the "spark gap" model is a mere cartoon of the complexity of a physical spark gap.

Tim
iMo:
Partially off topic: In mid 80ties colleagues of mine did simulation of  sub-micron GaAs semiconductor devices on an Sinclair Spectrum with 48kB ram and Basic. They did PhD with such an gear. Moral of the story - it is not about the gear but how a) good/well you can describe the stuff by the "theory of electromagnetic fields" and how b) good/well you can built a "system of differential equations".
PS: today the diff eq solver for b) is  fortunately ready to get off-the-shelf.. (Spice) :)
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