I was working on a transient circuit and I applied a 8kV, 2 ohm voltage transient on its input with a rise time of 10us and fall time of 50-100uS. It comes from a transient generator off mains so can provide an excess of 5kA if required.

(Stupidly) I was touching the circuit, and decided to do another test and everything seemed okay. I for some reason thought this time I better just check these caps are discharged and got an insulated test lead and shorted the capacitor out. It flashed this massive blue arc and made a loud bang as it did. Obviously, it made me realize how lucky I am and im still a bit sketched working with the circuit now.

I wanted to get some details from the community about how close to death I really was there, how much energy predictably would of been in the capacitors and energy it would of taken to be deadly?

I will provide some circuit details below:


simulate this circuit – Schematic created using CircuitLab

The transformer's secondary was shorted. It has 1 ratio of 1:1 and has 750u. It presents 0.2 ohms of impedance and has an inductance of 750uF. The capacitors are low ESR surge capacitors rated a 500+ volts. I dont know their ESR but its in the region of 1-2 ohm.

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    \$\begingroup\$ You're working with a circuit involving 8kV and poking it with your fingers? Lucky is an understatement. \$\endgroup\$ – Finbarr Apr 23 '19 at 23:01
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    \$\begingroup\$ I would strongly suggest to stop what you are doing immediately. \$\endgroup\$ – Ale..chenski Apr 23 '19 at 23:19
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    \$\begingroup\$ Honestly, something like that you may even have mild flash burns that you haven't noticed yet. This is a massively unsafe thing to be doing and you really ought to stop, double check your safety protocols, and have a second person in the room with you when you do anything with this stuff. \$\endgroup\$ – Hearth Apr 23 '19 at 23:28
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    \$\begingroup\$ Yeah, strange indeed :-) Seriously, if you're blowing fuses you're doing it wrong. Please don't rely on them. It sounds like you should start modelling the circuits beforehand to see what to expect, start following high-voltage ("arc-flash") safety procedures (including getting safety equipment), and (perhaps) find a mentor. \$\endgroup\$ – bitsmack Apr 24 '19 at 0:09
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    \$\begingroup\$ 20ma through the chest can reliably kill just about anyone, but some might die from only 10ma, if it hit right at the right time, like a baseball to the chest. If the current wasn't going from one arm to the other you would likely just get burned and shocked. not saying its a good idea, just trying to answer your question about "how close". \$\endgroup\$ – dandavis Apr 24 '19 at 2:50

how much energy predictably would of been in the capacitors

Assuming the capacitors divide the voltage and each is charged to 4 kV, the energy would be about 1 joule each. How much damage that would cause depends on how small and sensitive an area absorbed the energy. A baseball pitched by a professional would have well over 100 joules of energy and is routinely stopped safely by a glove, but could cause serious brain damaged if it is stopped by someone's forehead. A 22 caliber bullet has about the same energy, but would concentrate its energy in a much smaller area. A 1 joule arc would cause a nasty burn on a person's hand, but it would probably heal without causing any permanent disability. If someone managed to discharge a 4 kV, 1 joule charge with both hands it could kill them, but more likely wouldn't.


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