Re: Current regulation for Variac

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

Original poster: "Michael Rhodes by way of Terry Fritz <twftesla-at-qwest-dot-net>" <rhodes-at-fnrf.science.cmu.ac.th>


----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, October 06, 2001 9:10 AM
Subject: RE: Current regulation for Variac

Nearly all TV sets and video monitors have this PTC in them,
it is used for the de-gaussing coil when the unit is first turned
on.  Whether the current handling is sufficient, I'm not sure.

> Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Gary.Lau-at-compaq-dot-com>
>
> I ended up adding a PTC (Positive Temperature Coefficient) thermistor in
> series with the variac's input.  At room temperature, mine has a
> resistance of 1.0 Ohm to limit the starting current.  The unit rapidly
> heats up and achieves a .02 Ohm hot resistance under a full 20 Amp load.
>
> If you can't find the thermistor, you can add a 1 Ohm resistor in series
> with the variac input, and short out the resistor with a brief (<1 sec)
> time delay relay.
>
> Regards, Gary Lau
> MA, USA
>
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> Original poster: "Tesla by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <tesla-at-tezla-dot-com>
>
> Hi all.
>
> I have a small question about variacs. I have a 3,5kVA variac(Uin=230V).
> When i bring it online it sometimes(about 1/3 of the times) it draws so
> much
> current from the mains that my 10A fuse blows although i don't have any
> load,
> except the variac itself.
> Is there some way to correct the powerdrain with say a choke or
> something to
> make it "turn on" smooth? This problem is really annoying.
> Thought i hear with you guys first.
> Any help is appreciated.
>
> Thanks!
>
> //Matt
>
> Matthias "Tesla" Andersson
> http://www.tezla-dot-com
> tesla-at-tezla-dot-com
> -"Why Am I Glowing In The Dark?"
>
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