Date:         Sat, 5 Oct 2002 13:51:34 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: Sanity Check - Wire gauge for wiring SA headlights
Comments: To: DaveC <voicebox@DNAI.COM>
In-Reply-To:  <p0433013eb9c4ca6adedd@[192.168.99.102]>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 01:05 PM 10/5/2002, DaveC wrote:
>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".

Was it Tesla or Westinghouse?

>  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.

Well...it is, actually, if you're talking about shock hazard.  50-60 Hz is
right in the range that's most likely to cause ventricular fibrillation (a
defibrillator jolts the heart with a very strong DC pulse that totally
immobilizes it, in the hope that it will restart in correct running
order).  400 Hz such as is used in aircraft would be much safer.  In other
respects AC is safer because AC arcs tend to be self-extinguishing which DC
arcs aren't.  That's why switches carry so much lower ratings for DC than
AC loads (and lower for inductive than resistive loads because the
induction tends to continue an arc).

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

I have no idea what's being adopted, except that it will be some multiple
of 2.2 volts as long as they keep on using lead-acid batteries.  When my
dad was playing in submarines I think they were using 600-1000 volts open
circuit.  I know that Lucas was pushing for an intelligent-load system with
a 48v bus some years back.  Everything was to be connected to the bus.

david

--
David Beierl - Providence, RI
  http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"