one safety issue around AC vs DC.... if you have arcing, AC is self=20
extinguishing (zero crossings of sine curve). DC is not. DC will continue=
 to=20
arc until you shut it off.
DC (600 vdc) seems to be (not sure why) the choice for electric busses an=
d=20
trains around here (western canada).

jim.

On Saturday 26 April 2003 04:09 pm, you were heard to utter:
> DC is used for very high voltage (1 MVolt+!) long distance power
> transmission. For one thing, it avoids the skin effect.
>
> Bob Ammerman
> RAm Systems
>
> ----- Original Message -----
> From: "Tal" <tal@ZAPTA.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Saturday, April 26, 2003 1:49 PM
> Subject: Re: [OT] Saftey issues: AC vs DC
>
> > The main problem with DC is that it is difficult increase/decrease it=
s
> > voltage and therefore, it cannot be transmitted efficiently over long
> > lines (the old Edison vs Westinghouse debate
> > http://www.raintaxi.com/online/1997fall/bloodvolts.shtml). AC allows =
you
> > to transfer the same amount of electrical power with less loses on th=
e
> > wires(high voltage, low current).
> >
> > There are special cases when high power DC system are used (e.g.
> > conventional submarines with huge banks of batteries and voltages in =
the
> > range of hundreds of volts) but I don't think any country uses DC for
> > power transmission.
> >
> > As for danger, I think that if you compare DC and AC of the same volt=
age
> > rating, AC is more dangerous because the actual momentary voltage can=
 go
> > higher than the DC. This is because the AC voltage rating is typicall=
y
> > done by RMS which is kind of a average and is lower than the max peak
> > voltage.
> >
> > Hope this helps,
> >
> > Tal
> >
> > > -----Original Message-----
> > > From: pic microcontroller discussion list
> > > [mailto:PICLIST@MITVMA.MIT.EDU] On Behalf Of John Pearson
> > > Sent: Saturday, April 26, 2003 6:46 AM
> > > To: PICLIST@MITVMA.MIT.EDU
> > > Subject: [OT] Saftey issues: AC vs DC
> > >
> > >
> > > Is it true that DC is more dangerous, electrocution wise, than AC.
> > >
> > > Is it true that some countries use DC?
> > >
> > > If so, what is the voltage?
> > >
> > > Thanks
> > >
> > > John
> > >
> > > --
> > > http://www.piclist.com hint: To leave the PICList
> >
> > mailto:piclist-unsubscribe-request@mitvma.mit.edu
> >
> > --
> > http://www.piclist.com hint: To leave the PICList
> > mailto:piclist-unsubscribe-request@mitvma.mit.edu

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