Re: Power feed wire

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Jim Lux by way of Terry Fritz <teslalist-at-qwest-dot-net>" <jimlux-at-earthlink-dot-net>

At 07:03 AM 5/5/2003 -0600, you wrote:
>Original poster: "Christopher Boden by way of Terry Fritz 
><teslalist-at-qwest-dot-net>" <chrisboden-at-hotmail-dot-com>
>
>240VAC is fine, it's the Amperage you have to worry about :)
>
>Almost everything is rated for 300V (or 600V) because at 300V you can get 
>a spark without the wires touching (they have to be FREAKY close, but 
>don't have to actually touch) because 300V is the magic number where air 
>breaks down.

More accurately, at 300V, you can't get a spark in air no matter how close 
the electrodes or how low the air pressure. It's referred to as the minimum 
sparking voltage.

That said, I doubt that 300V and 600V were chosen as "regulatory 
breakpoints" because of this.

Another thing to think about...  240VAC in the usual household application 
is no more than 120V above ground.  120V * 1.4 = 168V peak, 240V * 1.4 = 
336V peak.  I sure wouldn't use wire with 300V rated insulation with a 
signal at 336V peak relative to ground.  Hmmm.. maybe that's why industrial 
extension cords designed for 240V (three phase) have 600 volt insulation, 
and inexpensive cords designed for 120VAC have 300VAC insulation?




>In all practicality, you could likely use the same cable at 1000V and not 
>have any problems, but I wouldn't go grabbing it at that voltage ;)


Following this logic one could also use bare wire, no?


>I'll bet that if you cut the ends off and strip the wires back when you 
>read the insulation each wire is rated for at least 300V. Watch your 
>amperage (if the cord is getting warm, you're pushing it too hard), and 
>run 240 all you like.