Re: Soft transformer turn on without a variac

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

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

I turn the power on with the variac turned down, then turn the variac up
to give power to the NST's.  If the breakers trip, they trip when I
initially close the switch giving power to the variac.  Also, I've been
using three 15/60s, but two of them already have internal PFC
(Franceformer has two 15/60 models - one with PFC, one without).

	- Bill V.



Tesla list wrote:
 >
 > Original poster: "Ian McLean" <ianmm-at-optusnet-dot-com.au>
 >
 > Hi Bill,
 >
 > Is this really a problem with the Variac, or with the inrush current of the
 > NST's ?  I too had breaker problems with a bank of two 15kV/60mA NST's until
 > I put power factor correction caps on the NST's, which reduces inrush
 > current significantly.
 >
 > This solution may have already been discussed previously, but I am new to
 > this list and have not had a chance to read all the list archives yet.
 > Apologies if I am off the mark.
 >
 > BTW, hello all from a new list member and avid coiler from down under !
 >
 > Rgs
 > Ian
 >
 > -----Original Message-----
 > From: Tesla list [mailto:tesla-at-pupman-dot-com]
 > Sent: Wednesday, 29 October 2003 6:43 am
 > To: tesla-at-pupman-dot-com
 > Subject: Re: Soft transformer turn on without a variac
 >
 > 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)
 >   >  >
 >   >  >
 >   >  >
 >   >  >
 >   >  >
 >   >  >
 >   >  >