Re: Overamping variac


Say I have .5amps at 120vac coming in and 2.25 amps at much lower vac
coming out, and the transformer is rated for 2.25amp, which amperage
should I be looking at to relate to variac rating?

Thanks Jack,
Paul


On Fri, 31 Mar 2006 22:56:10 -0500, "Jack Denver"
<nunuvyer@xxxxxxxxxxxx> wrote:

When you run thru a transformer amps drop as voltage rises and vice versa -
2.5 amps at 25 volts is about 62 watts. @ 125V, 62 watts is only 1/2 amp.
The variac sees only the 120V side of the transformer so it only is loaded
1/2 amp.


"Paul Monaghan" <monaghan@xxxxxxxxxxxxxxxxxx> wrote in message
news:0ctr225s25is8iq9ss5f8rtuvkpev39g3i@xxxxxxxxxx
Hi Jim,

So you would look at the amperage rating of variac and compare to amps
at the input rather than the output?

Agree on PII fan sturdiness, just burned out another one...

Thanks,
Paul

On Fri, 31 Mar 2006 20:58:49 -0600, jim schulman
<jim_schulman@xxxxxxxxxxxxx> wrote:

On Sat, 01 Apr 2006 02:48:33 GMT, Paul Monaghan
<monaghan@xxxxxxxxxxxxxxxxxx> wrote:

which
on the output draws from 2.25 to 2.37amps at 25-30vac.

That's about 2/3 amp at 120; you can run it forever, and it'll be the
fan, not the variac, that burns out.

BTW, I think they run closer to 18 volts -- P2 fans aren't that
sturdy, I've gone through 3 of them driving them directly off the
variac -- they tend to self destruct around 25 volts

.

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