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Re: What do you use for ballasting?



Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-uswest-dot-net>" <bert.hickman-at-aquila-dot-net>

Steve,

As long as you rectify the HV and use diodes to prevent backfeeding
into the supply this approach should work. However, there is a problem
with doing this directly from an AC source, especially with an ASRG. The
difficulty arises when the tank cap has been partially charged but the
voltage is insufficient to fire the main gap on the next presentation.
If, on the next charging presentation, the voltage on the partially
charged tank capacitor is significantly greater than the incoming HV
charging voltage, the capacitor will discharge back through the
secondary of the transformer, driving high energy pulses back INTO your
240 volt mains supply... and to those being served from the same
distribution transformer! 

One of the coilers who used to be on this list this some years back,
tried this approach without backfeed prevention - the resulting voltage
spikes blew out incandescent lights in his NEIGHBOR's house... :^)

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com



Tesla list wrote:
> 
> Original poster: "Steve & Jackie Young by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <youngs-at-konnections-dot-com>
> 
> Mike,
> 
> Well, if you want to be a pioneer and adventurous, try the following version
> of "8) Other", which may not need any ballast at all!?
> 
> Since you have an SRSG, consider adding more stationary contacts so the SRSG
> acts like a SPDT switch.  In position one, it will charge your tank cap
> completely independent of the primary.  In the next position, the tank cap
> discharges only into your primary.  And the cycle repeats, repeats, re...
> 
> In this arrangement, you never have the spark gap directly across your PT,
> so no power arcs.  And the secondary tank circuit is entirely isolated from
> the PT (position 2 bangs), so no RF protection circuits are needed.
> 
> I know this will work well with DC, and I am hoping you or someone will try
> it with AC and a properly phased SPDT SRSG.  PT current will be proportional
> to and limited by the break rate (and your voltage controller variac, of
> course), so you may need little or no ballasting.  (If I am overlooking
> something, someone please jump in and set us straight.)
> 
> --Steve
> 
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Monday, January 08, 2001 7:20 AM
> Subject: What do you use for ballasting?
> 
> > Original poster: "Mike Waddick by way of Terry Fritz
> <twftesla-at-uswest-dot-net>" <Mikew-at-winternet-dot-com>
> >
> > Hello all,
> >
> > I am now working on a Potential Transformer Powered Tesla coil. (2.5kva) I
> > now need ballasting. I know of most all methods. I am not on much a budget
> > and I would like some opinions. So my question to all of you is....
> >
> >
> > What one do you use and what one is the best?
> >
> > 1)Resistive
> > 2)Both Resistive and Inductive
> > 3)arc welder
> > 4)MOT's
> > 5)Variac (non cut)
> > 6)Variac (Cut)
> > 7)home made Inductor (if so what type?)
> > 8) other ______________
> >
> >
> > My specs on my coil are......(what type of ballasting should I use?)
> >
> > Tranny: 16.5kv PT run at 2.5kva and rated at 1.5kva continuous, Runs on
> 120v
> > ac
> > Primary gap: SRSG (not much more to it)
> > Primary cap: a .03mfd 35kv Maxwell pulse cap
> > Primary: Has ~14 turns of .025" copper tubing with a spacing of .25", 8"
> ID
> > Secondary: A 6" X 30" wound with 22awg wire on a Acrylic form
> > Topload: a 6" x 20" Al duct covered with Fiber glass and then coated with
> AL
> > tape
> >
> > For voltage controller I will be using a 50amp 120v in 0-140v out variac
> >
> >
> > Thanks A lot for all of you that respond,
> >
> > Mike Waddick
> >
> > Http://www.winternet-dot-com/~mikry
> >
> >
> >
> >