Re: AC vs DC and Toroid Question

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

Original poster: "Dr. Resonance by way of Terry Fritz <teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>


The 240 mA will be no where near enough drive current to keep your cap
charged.  We use 14 kVA to drive a 0.15 MFD cap.  Your alternative would be
a much lower rep rate but your output spark length will suffer considerably.

With this large coil you might consider a pole pig and external reactor for
the correct power input.

On a 12 inch dia. sec. you need a 34 x 8.5 inch toroid for effective match.

The sec. coil should be elevated above the plane of the primary coil approx
4.5 inches for correct coupling for max. spark output.

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
 >  >
 >  > I have a relatively large secondary coil-about 2500 ft., 12.5" dia, 50"
 > high.
 >  >   Have a small (14 dia duct pipe toroid but planning a larger one.
 >  >
 >  > I have several questions, please:
 >  >
 >  > 1)  Given a .15 mfd primary capacitor, a rotary spark gap, and a set of
 > four
 >  > 120v/7500v neon transformers in parallel producing 240 ma together,
would
 >  > there be a performance difference (1) operating the system AC versus
(2)
 >  > rectifying the current to produce DC, and slowing the spark gap down to
 >  > allow the
 >  > capacitor to charge fully between firing ?
 >
 > If you size the capacitor properly and use a sync rotary spark gap running
 > at 120pps, the capacitor _is_ fully charged at every firing point. The
 > performance in this case would be identical to if you used DC. The
polarity
 > of the capacitor charge doesn't seem to matter.
 >
 > AC systems that use an asynchronous gap do behave in the way you
described:
 > some of the bangs will be undersized or missing. This isn't usually a
 > problem with pole pig and MOT systems. Neon transformers are different;
 > under certain conditions they can produce oversized bangs and burn
 > themselves out, so you should only use a sync rotary or static gap with
 > NSTs.
 >
 > However, if you did rectify the output from the NSTs, you could probably
use
 > an async rotary safely.
 >
 >  >
 >  > 3) The program also indicates a power factor correction capacitor of
291
 > mfd.
 >  >   Is this to be at 500v or is a higher voltage recommended.  Do these
 > really
 >  > make a difference on transformer performance ?
 >  >
 > The PFC cap only needs to be rated for 120V AC. But be aware that PFCs
don't
 > give you any extra power, all they do is cause the system to draw less
 > current from the line. If the AC outlet you'll be using can supply enough
 > current there's no need to bother with PFC.
 >
 > Steve C.
 >
 >