Date:         Sat, 5 Oct 2002 10:05:59 -0700
Reply-To:     DaveC <voicebox@DNAI.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         DaveC <voicebox@DNAI.COM>
Subject:      Re: Sanity Check - Wire gauge for wiring SA headlights
In-Reply-To:  <5.1.0.14.2.20021005105043.03f723e8@pop1.attglobal.net>
Content-Type: text/plain; charset="us-ascii" ; format="flowed"

>Incidentally, this helps illustrate why the trend is always toward higher
>system voltages:  the power losses in the wiring are equal to I^2 * R -- if
>you double the system voltage you can halve the wire size / weight / cost
>of copper without any additional losses (or keep the same size wire and
>experience only one-quarter the power loss).  That's why we went from
>six  volts to twelve, why large vehicles and boats use 24v, and why there's
>a push to have new vehicles use a 48v system (which is beginning to get
>scary in terms of shock potential).
>
>It's also why they use a million or so volts to carry AC power across
>country, and 5,000 volts across town.  And why Edison's DC generator system
>was doomed from the start -- he couldn't use transformers to boost the
>voltage for transmission and had to generate it at the same voltage it was
>to be used, making it necessary to have a generating station every few blocks.

-=-=-=-

Nikola Tesla's invention of the AC polyphase power generation and
distribution system we use today was a real fight to get accepted, in
the face of Edison's "marketing". It is rumored that Edison paid
street urchins to capture cats from the streets of NYC and he would
electrocute them, claiming that it was the AC system was more
dangerous than his DC system.

Technically, AC is more efficient over long distances (ie,
high-tension power lines); less power loss.

BTW, from what I remember, the "official" adopted voltage for future
vehicles is 36 volts, not 48. Go figure...

Dave
--
Dave Carpenter

"Any sufficiently advanced technology is indistinguishable from
magic." -- Arthur C. Clarke