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RE: [TCML] Variac

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> > _______________________________________________> > Tesla mailing list> > Tesla@xxxxxxxxxxxxxx> > http://www.pupman.com/mailman/listinfo/tesla> > _______________________________________________> Tesla mailing list> Tesla@xxxxxxxxxxxxxx> http://www.pupman.com/mailman/listinfo/tesla_______________________________________________
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