Re: Quick variac question

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Christoph Bohr" <cb@xxxxxxxxxxxxxxx>

Hello robert

Sorry, but this can not be done.
While you might be right that the core material would be
adequate to wind a 240V variac with half the amperage,
the winding itself is not.
There is a vertain volts/turn ratio for any given core that
must not be exeeded. Overvolting by 100% would
by far exceed these limits and lead to massive current
draw when the core saturates.

The other way around is not true, either.
( running a 240V variac on 120V )
While this can be done it will not double your available
current as this is limited by the wire diameter that was
used to wind the core. Running at the designed current
this can be done without bigger problems apart from the
additional wight you might have to move around....

However, if you have two 120V variacs you can stack
them to get one 240V unit with the same current rating
as a single unit, thus doubling power handling capability.

I hope this helped

best regards

Christoph Bohr


----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Wednesday, May 18, 2005 5:59 PM
Subject: Quick variac question


> Original poster: "Robert Hanford" <pomnept@xxxxxxxxxxx>
>
> This might seem like a stupid question:
> If I have a variac rated at 120V, 20A,  can I run it at 240A, 10A,  the
> power being the same? Any answer appreciated.
> Robert Hanford
>
>
>