RE: Variac current and VA rating

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

Original poster: "Ray Haynes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ray.haynes-at-home-dot-com>

If you are pulling 9A from the brush output then 9A is flowing from the 0V
end terminal to the brush. The only real magic is that it won't necessarly
take 9A in to produces that 9A out, that depends on the voltage setting. The
input to output current is inverserly propotional to the input to output
voltage just like a regular transfomer (Vin/Vout = Iout/Iin).
So your example of 120VAC/40VAC = 9A/3A is correct. If we look at the
current flowing in the windings we would see 3A in the wire from the 120VAC
connection to the point where the brush is touching and 9A from that point
to the 0VAC connection (for a setting of 40VAC out).

Hope that helps,
Ray


> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Thursday, May 31, 2001 11:55 AM
> To: tesla-at-pupman-dot-com
> Subject: RE: Variac current and VA rating
>
>
> Original poster: "Pete Komen by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <pkomen-at-zianet-dot-com>
>
> Hello Shaun,
>

***SNIP***
> For Mark,
>
> I was aware that some people run variacs over the rated VA.  I
> don't need to
> do that yet.  I have a 20 amp 140vac output variac also.  The
> basic question
> is: for a variac input of 120vac at 3 amps and an output of 40vac
> at 9 amps
> (ignoring losses), what is the current in the windings between
> the 0vac and
> 40vac points?
>
> Regards,
>
> Pete
>
>
***SNIP***