Note that if you want to save on copper and are only interested in delivering the same power with the same percentage of wire losses, then going 4 times up in voltages allows you 16 (!) times smaller wire surface area, because current is 1/4 but also 4 Volt loss in a 48V system is the same percentage as 1V in a 12V car. So if you needed a 1/4" diameter wire (2 AWG) in a 12V car then you only need 1/16" diameter wire (14 AWG) for 48V to transport the same power with the same losses. In different words: going up 4 times in voltage means you only need 6% of the copper for the same performance. Now you may get why distribution lines are so high voltage. Cor.
On Sat, Oct 5, 2024, 6:50 PM Lee Hart via EV <ev@lists.evdl.org> wrote: > >> On aircraft, 28 volts (24 volts) has been the standard low voltage > forever. > >> It is the standard on specialized military vehicles and equipment as > well. > > Also in large trucks and buses. > > > "42 volts" is the threshold for "low voltage" in the US National > Electrical > > Code, but as I recall, that is for AC rather than DC. > > Yes, also UL and ETL. They specify 30vac or 42vdc peak as the maximum safe > limit for voltages you can touch. > > > I suppose if you are going to make a departure from the industry > > standard of 12 volts, then why not go all the way to 48 volts. > > 48v actually exceeds the "low voltage" classification for NEC, UL, and ETl > etc. There is also a problem with arcing. Switch, relay contacts, fuses, > circuit breakers, motor brushes, etc. are all typically limited to 30vdc > max before arcing will not extinguish itself. > > To me, it makes more sense to increase vehicles from 12v to 24v, in line > with a huge number of other vehicles. There are already lots of 24v > accessories. Going to 48v means essentially no standard components or > accessories can be used. > > That said... The auto companies routinely ignore electrical safety > standards. They use undersized wire gauges, combustible wire insulation > that melts at lower temperatures, inadequate fuses, switches and relays, > etc. > > Lee > -- > Excellence does not require perfection. -- Henry James > But it *does* require attention to detail! -- Lee Hart > -- > Lee A. Hart https://www.sunrise-ev.com > > > _______________________________________________ > Address messages to ev@lists.evdl.org > No other addresses in TO and CC fields > HELP: http://www.evdl.org/help/ > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20241005/991da995/attachment.htm> _______________________________________________ Address messages to ev@lists.evdl.org No other addresses in TO and CC fields HELP: http://www.evdl.org/help/
