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RE: [TCML] Variac

the light bulb sounds like a much cheaper idea for me at the moment. but i am still curious about the relay thing.  could you possibly draw a diagram.  I am a visual kind of person. thanks

ok so the variac does not have a company name that i can see.  
here is a pic of it

on a side note and probably a new thread
i got a 1kva transformer that goes from 120 to 240 or something like that.
  I want to remove the core and rewind it to be an HV tesla coil power supply.  but the core is potted in some weird stuff.  it is almot like sand. where each grain is fused to the next.  its hard as a rock.  any ideas on how to make it dissappear so I can get the core out.

here is a photo of the potting.  http://i139.photobucket.com/albums/q295/JHowson/100_0058.jpg

-------------- Original message -------------- 
From: William Noble <william_b_noble@xxxxxxx> 

> a simpler solution, in a dorm environment, is to put a light bulb in series with 
> the variac, and then after start up, short out the bulb> From: 
> sparktron01@xxxxxxxxxxx> To: tesla@xxxxxxxxxx> Subject: Re: [TCML] Variac> Date: 
> Wed, 29 Oct 2008 01:41:24 +0000> CC: > > Jay > > It is the inrush on the Variac 
> when turned on.> Variacs, depending on many factors, may turn> on without a 
> whimper, or may have a severe> turn on transient when energized> (as much as 10X 
> FLA). The start up> transient includes magnetic saturation, coil > resonance (or 
> ferroresonance), and higher> order harmonics which in general can wreck> havoc 
> on the circuit feeding the variac.> > The solution is what is called in trade a 
> "step start"> relay. Install a resistor on order of 10 ohms, 25W> in series with 
> variac. Install a motor contactor or> BEEFY 120VAC power relay in circuit; wire 
> the coil > in parallel with 120V winding of variac> and wire a NO (normally 
> open) contact of this relay> across (in parallel with) the surge limiting 
> resistor.> > When you turn on now, inrush is limited to ~12A, voltage> builds 
> based on L/R decrement across variac until> sufficient voltage is across variac 
> to allow relay to> pull in, bridging the surge limiting resistor and> providing 
> full power to variac. I would> also install a 20A 250V ABC ceramic cartridge 
> fuse> in series with variac; available at Radio Shack.> The fuse will limit the 
> heartburn, hate, and nashing of> teeth and maintenance being PO'd about> 
> resetting the breaker...AGAIN... ;^D.> > Regards> Dave Sharpe, TCBOR/HEAS> 
> Chesterfield, VA. USA> > > -------------- Original message 
> ----------------------> From: jhowson4@xxxxxxxxxxx> > Ok this is attempt 3 my 
> e-mail keeps saying that there was a sending error. so > > if 3 of the same 
> message were in fact sent i am sorry.> > > > Ok so i think that this so called 
> surge is the culprit since at the time of the > > breaker being blown I was 
> trying to figure out where a weird sound was coming > > from and this entailed 
> turing it on and off. learing from my mistakes i won't > > be doing that 
> again... ever...> > > > How much current is the norm if nothing is plugged into 
> it? If the unit is rated > > for 22.5 amps why is it not pulling that much power 
> all the time?> > > > How does starting the variac with it turned up help. I 
> understand what you want > > me to do but I am curious as to why it works.> > > 
> > Even if the surge current was the culprit i want to be sure before I plug it > 
> > back in and the people start asking why stuff blew.> > > > Thanks, > > Jay. H> 
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