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Diode/SCR volt drop for current off curve

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Member level 5
Jul 22, 2014
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Given a curve of on voltage V current like figure 7 here...

Is there a way of reasonably accurately extending this data beyond the curve to give say in this example the volt drop for a 1kA pulse. I didn't know if there is an underlaying relationship that allows this, or is my only option measurement.

O.K. Vishay VS-40TPS16PbF
Assuming constant Vd + I*Rd above 100 A gives probably a good estimation. Notice that Rd increases with temperature.

This graph ?


Short answer is no, you cannot infer specifications, and those graphs are
"typical" not worst case. The best way to get an answer is contact manufacturer
for characterization data. And then thats not typically tested, all the data that is.

If you want reliability then you have to test for it. Or know the characterization
encompasses all worst cases......

Parts may not be bonded for a 10X outside graph pulse condition, hoptspot generation
not discussed or speced.......tell me which bridge or elevator or plane you are going to
put this in so I can avoid them....:)

Regards, Dana.
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I didn't hear about worst case specs.

In addition to post #4, some points should be considered. If you are looking at switch-on behaviour, di/dt behaviour must be observed. Turning the SCR on with full current causes unequal current distribution with local overheating and possibly device destruction. Carrying 1 kA for longer than a few 10 µs causes heavy chip heating and further increase of rd. In other words a static I/V curve above 100 A has limited validity.

Hint for OP, the production engineer typically the owner of characterization data,
you can as a customer typically talk to them directly, once you wade thru a few
layers to get the phone number. Contact local FAE or Sales Rep or Regional office.

Regards, Dana.

The data sheet clearly sets out 500A half sine pulse ( 5mS ), this is 707A pk, with no reverse applied volts immediately afterwards

this is likely the limit for this device.

An 100A SCR will likely allow a 1kA peak for 5mS

Extrapolation assumes things which may not be true and
this can only be found by experiment. Somebody else's
preferably as such things cost time and money.

In the case at hand I'd wonder / worry about competing
failure mechanisms, #2 passing #1 as pulsed heat changes
from averaged and distributed across the close-in thermal
mass to localized adiabatic as some secondary effect like
runaway rolls on, etc. Linear, in the face of so much square
law, exponential, feedback loop type stuff when you push
material / physics limits, seems like a bad bet. So "No"
I'd call "No" but "Yes" I'd say "maybe" to any analysis.

Besides, blowing stuff up is more fun than your average
multiphysics FEA not to mention cheaper and quicker.

Charts labeled Maximum, so what are your pulse train conditions ? Fig 5 seems to imply no
but still that is stated with initial Tj @ 150 C, best to consult manufacturer......

Regards, Dana.
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