Re: Soft transformer turn on without a variac

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

Original poster: Bill Vanyo <vanyo-at-echoes-dot-net> 

Hi All,

	Anyone remember this discussion?  Basically, the problem I want to
solve, and that was discussed previously, was how to turn on power to a
variac without tripping breakers.  For my own setup, I have a variac
rated 50 amps 240 volts fed from a 30 amp 240 household line (electric
clothes dryer).  I set the variac at half way to step down to 120.  I'm
using 3 (soon 4) unmodified 15/60 Franceformers.

	What I'm looking for, if anyone can help me with this, is a cut and
dried plan using readily available parts (part numbers & sources would
be ideal), a la Terry's NST Protection filter - just something so I can
turn on power to the variac (turned down to the low end) without
tripping the house breakers.  Right now I'm using a big old knife
switch, which more often than not trips the breaker.

	I suspect many other novice coilers could benefit from a solution to
this too.

	Thanks,
	Bill V.

Tesla list wrote:
 >
 > Original poster: "Rick W by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<potluck-at-xmission-dot-com>
 >
 > Hi Peter,
 >
 > I had that problem also with a stack of 2 variacs for 120 volts and a stack
 > of 6 variacs for 240 volts. The scheme I'm currently using is shown in the
 > link. For 240 volts I'm using an 18 ohm resistor. I believe the wattages can
 > be less but that's what I had in the resistance range I wanted. This works
 > really well. I don't add load (ramp up the variacs) until both contactors
 > are pulled in.
 >
 > http://xmission-dot-com/pub/users/p/potluck/pics/rampup.jpg
 >
 > I see Scot D. is using an inductor. I tried that and found the same problem.
 > The current draw feeding six 240 volt paralleled variacs is rather low after
 > the intitial small spike. Much lower than I had expected so these worked
 > very well.
 >
 > Also, the post about Negative Temperature Coefficient Thermistors in power
 > supplies is very interesting. Very interesting indeed. I too will be looking
 > into that.
 >
 > Rick W.
 > Salt Lake
 > ----- Original Message -----
 > From: Tesla list <tesla-at-pupman-dot-com>
 > To: <tesla-at-pupman-dot-com>
 > Sent: Wednesday, July 23, 2003 6:53 PM
 > Subject: Soft transformer turn on without a variac
 >
 >  > Original poster: "Peter Terren by way of Terry Fritz
 > <teslalist-at-qwest-dot-net>" <pterren-at-iinet-dot-net.au>
 >  >
 >  > Hi all.
 >  > For my 5 kW museum
 >  > coil,
 >  >
 > <http://members.iinet-dot-net.au/~pterren/Scitech.htm>http://members.iinet-dot-net.a
 > u/~pterren/Scitech.htm
 >  > ,   I need to have a single switch for turn on preferably without a 
variac
 >  > to keep things simple for the staff.  The present system has solid state
 >  > relays but is complicated and unreliable. I need to turn on the motor
 > first
 >  > then a couple of seconds later soft turn on the power to the transformer.
 >  > Even switching  on power to a normal variac gives a spike that will trip
 > my
 >  > lower current breakers. The whole system will have to be electrically
 >  > quiet.  Does anyone have experience with inrush limiters or have other
 >  > suggestions?
 >  >
 >  > Cheers
 >  > Peter (Tesla Downunder)
 >  >
 >  >
 >  >
 >  >
 >  >
 >  >
 >  >