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Every year divisible by four with remainder one, adventurous geeks hold an outdoor festival in the Netherlands. This year, about 6000 people are expected to attend a long weekend.
Among them will be a group of experimenters who will be testing a 42 volt direct current grid. Specifically, a cluster of tents within the festival will receive approximately 50 × 4 Amperé supplies and 8 × 16 Amperé supplies. Hopefully, this will be run by solar power but there will also be a backup generator. Switching a high load of direct current is more complicated than alternating current and losses around the example MOSFET circuit are expected to be less than 0.2W per junction. Although people are expected to bring together previously untested circuitry, it is hoped that pieces of the project will inspire multiple direct current grids in more permanent locations.
Hopefully, electrocution or voltage drop doesn't halt electrical distribution at the festival.
(Score: 2, Disagree) by tekk on Sunday July 02 2017, @05:48AM (8 children)
DC's generally safer because you don't have a single 'live' wire, you have to actually complete the circuit, unlike AC. Plus at 42 volts I don't think that's enough to overcome the resistance of unbroken skin, is it? So unless you're like, bridging the wires across a pair of open wounds you should be pretty much fine.
(Score: 4, Informative) by Anonymous Coward on Sunday July 02 2017, @08:51AM (4 children)
Ah, what???? You always have to complete the circuit!!
Yes, there is.
https://www.physics.ohio-state.edu/~p616/safety/fatal_current.html [ohio-state.edu]
Welders insulate themselves from their workspace too. Even stick welders, that work with 12 or 24V. AC or DC, doesn't matter. The difference is that if you are being electrocuted by an AC source, it is generally easier to guess by an external observer.
(Score: 0) by Anonymous Coward on Sunday July 02 2017, @11:57AM (3 children)
so no. you don't really have to 'complete the circut' like you do with dc.
just to be standing on the ground will do it.
(Score: 0) by Anonymous Coward on Sunday July 02 2017, @03:03PM
Same with DC.
(Score: 0) by Anonymous Coward on Sunday July 02 2017, @04:01PM
Which has completed the circuit because the second half of the circuit is the earth itself.
(Score: 0) by Anonymous Coward on Monday July 03 2017, @08:06AM
That's a property of the circuit, not of AC.
If you are using the ground as one half of the circuit, touching the other side while standing on the ground will complete the circuit, whether you are using AC or DC.
If you are not using the ground as one half your circuit, you need to touch both sides to complete the circuit, whether you are using AC or DC.
(Score: 2) by isj on Sunday July 02 2017, @12:44PM
DC's generally safer
It really depends on the expected failures.
AC has points in time (50 or 60 times a second) due to the waveform where the voltage is zero, so it is more difficult to sustain an arc. If you want to avoid arcs then go for AC (or use better spacing).
It is my understanding that DC tends to burn skin but not cause muscle cramps, while AC generally doesn't burn skin but does cause cramps.
So what is safer really depends on the environment, voltage and amps.
In either case: don't try to make Mr. Fork close friends with Mrs. Outlet. Don't lick live wires. Don't pee on electric fences.
(Score: 1, Insightful) by Anonymous Coward on Sunday July 02 2017, @03:00PM (1 child)
Correction, my friend: ANY electrical system, AC or DC, that uses one pair of wires has a SINGLE live wire. The other wire is neutral. Touch the live wire and you risk current travelling thru you as the electricity finds an alternate path other than the usual one. Most people call this "ground". Source: Electrical Engineer.
(Score: 2) by Osamabobama on Monday July 03 2017, @05:38PM
Would this be a good place to touch on capacitance as a factor in AC circuits? Higher frequencies exhibit less resistance across a capacitor (or, perhaps, an ungrounded human) than do lower frequencies. Not being (or having consulted with) and electrical engineer, however, I am not the best person to explain this.
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