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The company I work for builds products that typically have integrated fuses or circuit breakers. During our product validation testing, we would like to begin integrating a test which will basically be an AC short circuit, in order to get an idea of the effect of the short on our product (for example, how many milliseconds will it take for our circuit breakers or fuses to react to the short circuit). How can I safely create a Line to Neutral short of a live AC circuit?

(The lab that we will be testing in is fully isolated electrically from the rest of the building, and has all of the circuit protection that we will need. The lab is built like a bunker and anyone near the testing will be wearing the appropriate PPE. We know that this testing will be dangerous, and we have all of the safety aspects covered.)

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  • \$\begingroup\$ And you don't want to buy a instrument which can do it for you? Like: megger.com/eu/products/… \$\endgroup\$
    – Dejvid_no1
    Nov 1, 2016 at 20:52
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    \$\begingroup\$ so what's wrong with mains lead to croc clips? \$\endgroup\$
    – Neil_UK
    Nov 1, 2016 at 20:54
  • \$\begingroup\$ Use a switch rated for more than the current of the external breaker protecting the EUT. \$\endgroup\$
    – The Photon
    Nov 1, 2016 at 21:01
  • \$\begingroup\$ In general, you're going to need a test rig that can safely and repeatedly withstand the short circuit rating of the device under test. Off the top of my head (too lazy to Google), here in the UK that's something like 65kA for industrial quality switchgear. I think the old ceramic fuseholders were only about 1kA, something like that. And so on. It's impossible to know what rig you need without knowing the expected (and thus device rated) short circuit current. There isn't just one short circuit, it depends on the impedance of the supply upstream of the device, basically. \$\endgroup\$
    – Ian Bland
    Nov 1, 2016 at 21:06
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    \$\begingroup\$ @SpehroPefhany if they want to do this properly, they shouldn't be using the general electrical supply; the rig should be one that generates the fault current for test purposes. This is not a trivial engineering matter and I would expect it to be designed by people with considerable expertise. I'm pretty sure that when I purchase a breaker rated at 65kA, they did something more scientific than stick a big screwdriver across the terminals, if you see what I mean. \$\endgroup\$
    – Ian Bland
    Nov 1, 2016 at 21:36

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