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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: 4, Informative) by bzipitidoo on Sunday July 02 2017, @04:31PM (3 children)
In the late 90s, there was a program afoot to move automobile electric systems from 12V DC to 42V DC. There is a 6V standard, but that was phased out in favor of 12V more than 60 years ago. They picked 42V because that was about the highest voltage that was not too dangerous for people. Yes, current kills, but voltage is what overcomes resistance. Would've liked to go higher, but 42 is high enough to realize a whole bunch of improvements. The wiring can be much thinner, and yet carry more power. Lot of components that have to be belt driven by the engine in a 12V system can instead be driven by small electric motors at 42V, as needed at any speed within its range, instead of being stuck with continuous operation at whatever RPM the combustion engine is running at, or having to work around the limitations with heavy clutches and the like. Would move the A/C, water pump, power steering, and the valves to electric, and combine the starter and alternator into one winding, and integrate it into the flywheel. The fuel pump and radiator fan were transitioned to electric decades ago, fuel pumps in conjunction with fuel injection to obtain the higher pressures needed.
But the program fizzled out, and manufacturers never made the change. One big problem was that the filaments for incandescent headlights have to be thinner at the higher voltage, which makes them very short lived. Too easy for a bump in the road to break the filament. It wasn't just headlights, it was all the lights. Of course, now we have LEDs. Meantime, electronics for changing voltage levels have improved, allowing more to be done with the 12V system, making the 42V system less of an improvement. We may be 5 years away from a mass switchover to electric cars, so there's little point in switching standards now.
(Score: 0) by Anonymous Coward on Sunday July 02 2017, @07:17PM
Good points. One you left out is that switches and mechanical relays wear out more quickly at higher voltages because arcing becomes more of a problem. Open a closed switch at 48 volts and there will be arcing. Not so much at 12 volts.
(Score: 0) by Anonymous Coward on Monday July 03 2017, @08:19AM
My mid-engined car has electric power steering (it's located about as far from the engine as you can get), so that's no problem.
As for the coolant pump, I would prefer it running at the same time as the engine, not on some electric motor on a separate fuse.
(Score: 1) by terryk30 on Monday July 03 2017, @10:35AM
And although 42 may sound a bit precise for an "about" quantity, it's peak V for 30 VAC (rms), which seems to be the "traditional" rule-of-thumb* for the safe/unsafe "threshold".
*A strong enough rule-of-thumb that it also seems to be the unofficial limit below which you do not require professional certification to work on systems (in some jurisdictions at least?).