Short Circuit Current simulator

Since you think the OCPD will open in a half cycle, how about a big capacitor and DC?

If DC wouldn't adversely effect how the breaker functions under a short-circuit condition, I see no reason why this wouldn't be acceptable. Anybody know the answer?

My device basically just needs to withstand this 1/2 cycle blast without breaking apart or starting a fire. If a UL489 breaker subjected to 18,000 amps at 300V DC and not open for at least 8mS (and hopefully open within 16mS), then I believe this should work.

If DC wouldn't adversely effect how the breaker functions under a short-circuit condition, I see no reason why this wouldn't be acceptable. Anybody know the answer?

My device basically just needs to withstand this 1/2 cycle blast without breaking apart or starting a fire. If a UL489 breaker subjected to 18,000 amps at 300V DC and not open for at least

8mS (and hopefully open within 16mS), then I believe this should work.

Dont most of those larger breakers use a microprocessor to open the breaker during the zero crossing to minimize the arc?

peace dawg

That is probably true for main circuit breakers in a larger load center. I'm wanting to use a standard single pole 277V-rated thermal- magnetic branch circuit breaker.

I've seen something like this done before. It used a transformer similar to what you'd find in a spot welder, more or less a scaled up version of the classic Weller soldering gun. It consists of a big beefy primary with the secondary being just a couple of turns of very heavy wire around the core. A friend of mine built a small spot welder using a large microwave oven transformer with the HV secondary replaced with I think two turns of big heavy copper wire and he got a bit under 2,000A out of that, so you'd clearly need something bigger. To control it he used an AVR microcontroller to watch the 60Hz line frequency and turn on a triac driving the transformer primary for the desired number of cycles. The problem with this is that you won't get 277V, but only a few volts.

The other way I know of to get pulses of very high current is to use a bank of large capacitors.

Chuck, Hi, whichever way you look at it, if you insist on 277 volts at 18kA you will need a 5MVA load . That's big! As others have suggested there are ways of getting 18kA at very low volts. The easiest way is to go to a bona fide testing laboratory and let them test it for you. There are protected test bays for this kind of things...what you are suggesting can get dangerous when things fly around. The physical forces due to 18kA can be extremely strong.

Take care please,

Daniel

Correct. And, depending on exactly what the OP needs to test, clearing an 18 kA fault at a volt or two isn't quite the same as clearing one at

277 volts.

The question that I would ask you is "Why do you want to do this test ?" If you have a commercial circuit-breaker it will have a rating allocated to it by the manufacturer. If this rating does not match your requirement the right approach is to ask the manufacturer. It may be that they have tested it for the rating that you require.

It is very difficult to do any meaningful tests outside of a proper short-circuit station. As others have pointed out it might be possible to genrate the current level that you want at low voltage, and this might be a meaningful test of the physical strength of the circuit-breaker, providing the method of making the current, and the inherent power factor of the supply were correct, but it would not guarantee the the fault current would be cleared under all possible conditions.

John Rye

nipple clamp

This is not a simple problem unless you have a source capable of 18KA at

277V. It is reasonably easy to provide 18KA peak, or to provide 277V but not both. The actual interruption will occur at current zero and at this time, it is necessary to provide the full voltage across the contacts when they open.

Daniel and Paul are right on.

May I ask why you want to do this?

About 5 Megawatts is more than the average experimentor should even dream about. This is BIG test lab stuff for the experienced Qualified test labs.

And without the real power available to explode the failing device no amount of testing will prove anything.

As Don asks, whats the the point?

john g.

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One of the best brand of circuit breakers here in EU are Siemens. They usually clear the impulse short circuit current before the main fuse (blow fuse here in Greece) blows, other brands won't. price is 3 euros each.

I installed a Siemens panel for a friend a couple years ago and was really pleased with the thing overall. We don't have main fuses here, it's all breakers, and as far as I know, no faults have occurred to test the function, but everything looked and felt really well made. It's enough to make me want to replace my aging panel.

I also like their switches, plugs etc. I usually install the Delta Arte, which are the cheapest set, but there are more expensive, and the cheap-cheap Super series. They have no screw terminals, but push-in which is very good, because the higher rated receptacles here, 16 A @ 230 V have quite some power to handle. Here, we install a GFCI breaker as a main breaker for the whole residence, called RCCB (Residual Current Circuit Breaker) with a trip current of 0,03 A. I am now doing my sister's house and I will install a LAN receptacle at each bedroom.

In the US, the push-in terminals are garbage, at least now they're illegal for anything higher than 15A. The contact area is way too small, and the aging contacts tend to corrode, heat, and lose spring tension which leads to more heat and corrosion. I hate to think how many house fires those things have caused.

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The same I have noticed happens with cheap screw terminal plugs, reputable manufacturers like Legrand maybe are better. Reputable manufacturers like Siemens should be free of trivial faults, anyway in my house I have changed all plugs etc. with siemens with no problems sofar for 5+ years with electric radiators in winter. Cheap knockoff tirkish or chinese plugs with push in terminals are totally crap, of course, they sometimes leave a smoke trail on the wall if a radiator has been used on this plug.