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Re: Maggies and such
On 15 Aug 00, at 18:04, Tesla list wrote:
> Original poster: "Jason Johnson" <hvjjohnson13-at-hotmail-dot-com>
>
>
> ----- Original Message -----
> From: Tesla list <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Tuesday, August 15, 2000 12:58 PM
> Subject: Maggies and such
>
>
> > Original poster: "sundog" <sundog-at-timeship-dot-net>
> >
> >
> > Hi all!
> >
> > A question on magnifiers....
> >
> > I am guessing that the secondary and tertiary coils have to be at the
> > same resonant freq. Makes sense to me that they would be. But will
> having
> > different inductances (a big fat driver with mediocre turns and a tertiary
> > that's wound with finer wire for more turns so they have the same res.
> > freq)..ideas? I'm wanting to get the surge impedance down on the driver
> so
> > it can be coupled tighter. Yep, gap losses go up, but this is for
> > examination more than long sparks.
> >
> > Caio!
> > Sundog
> >
> I know that this is the third or fourth time that this individual message
> has come up on the list but Richard Quick probably knows a thing or two
> about magnifiers:
Without analysing the following piece too deeply it is worth
noting the date of publication. It is also worth noting that
experiments and discoveries since this piece was written call
some of its tenets into question (John Freau and I mentioned
the coupling thing earlier). It is further worth noting that
analyses which speak of tight primary/secondary coupling
enabling the free resonator to be treated as a separate entity
without invoking Dr de Queiroz's multiple resonant network
theory assume that the primary is fed by a *voltage source*
(e.g. low impedance signal generator) which a primary
capacitor most certainly is not.
If anyone doubts this and still thinks there's something
arcane about magnifiers, try the following:
- pick two of your resonators out at random.
- stick a topload on the one which you will use as the extra
coil (if you are going to run it with a topload).
- elevate it on an insulator
- setup the other resonator with a primary as if you were
going to build a 2-coil system.
- connect the top of this resonator to the base of your extra
coil.
- use a scope and signal generator to find Fr of your
secondary+extra coil hooked together.
- tune your primary to this frequency using whatever primary
cap you wish by tapping to the appropriate inductance
- rig up a gap and transformer and fire it up.
- adjust gap, coupling and primary tapping for best results as
usual.
Malcolm
> DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD
> Date: 28 Dec 93 12:51:00
> From: Richard Quick
> To: All
> Subj: 10KVA Tesla Coil
> DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD
> Well I hope everyone had a happy holiday. I am now recovered
> enough to post some more specific info on Magnifier construction
> and operation. I have covered some general material on this
> revolutionary Tesla coil system, but will now endeavor to throw
> out some specific pointers for those of you who have an interest
> in this much more efficient RF power processor.
>
> As I have mentioned the Magnifier is a three coil system. The
> primary is excited from a Tesla tank circuit, the secondary coil
> is inductively coupled to the primary, and the extra coil is top
> loaded on the secondary in such a fashion as to be uncoupled
> completely from the primary/secondary "driver" coils. The extra
> coil is base fed by transmission line, which can be anything from
> Litz wire, copper pipe, or heavy DC transmission wire.
>
> The keys to getting an efficient Magnifier setup in operation can
> be listed fairly easily: Close coupling between primary and
> secondary, good gap quenching, and proper impedances in the
> secondary driver and the extra coil.
>
> Coupling in Tesla magnifiers must be tight. Classic style
> vertical helix primaries are very practical for use in Magnifier
> systems, but heavy insulation between the coils must be used to
> prevent flash-over. The close coupling reduces somewhat the VSWR
> in the driver secondary, and the 1/8th wave output contains
> substantially less voltage than a normal 1/4 wave Tesla system,
> but the close physical proximity between coils means flash-over
> will be a problem. Use several layers of polyethylene plastic
> around the secondary, and insulate the top primary turns with
> heavy vinyl hose. It has come to my attention that tapping the
> primary coil from the bottom turns, and heavily insulating the
> top turns, reduces flash-over. (now gee, why didn't I think of
> that?)
>
> Good gap quenching is a must. Because the coupling is so much
> tighter in Magnifier systems, more strain is put on the main
> system spark gap. If ever there was a need for exotic spark gap
> systems this is it. Quench times must be low, low, low, in order
> to trap the maximum energy into the secondary driver. An un-
> quenched (closed) gap will allow energy in the secondary back
> into the primary/tank circuit. This must be prevented. In
> Colorado Springs, Tesla used a pair of air blast gaps in series
> with a massive rotary. He kept pushing his line frequency higher
> (he had a massive, variable speed alternator in the lab),
> increased his break rate (up to 50,000 bps) and kept the energy
> delivered per pulse down to a minimum. The reason he strove to
> keep the energy per break down was to prevent overloading his
> gaps. As energy per break (voltage * current) increases, quench
> times decrease and efficiency in the Magnifier drop off. The
> increase in the number of breaks per second allowed the total
> energy processed to climb to unheard of levels, with unheard of
> performance and efficiency.
>
> The next key point to building and operating a small to medium
> Tesla Magnifier is proper coil impedances in the secondary driver
> and extra coil. The extra coil must have a higher impedance than
> the secondary driver. The extra coil must be lower in resonate
> frequency.
>
> I have mentioned here that the 1/8th harmonic output of the
> secondary driver coil matching the natural 1/4 wave resonate
> frequency of the extra coil is the most efficient mode of
> Magnifier operation. This is true, but don't get bogged down with
> it. This system will work and fire (within reasonable limits)
> with any extra coil that has a higher impedance and inductance
> that the driver secondary. Let me give some tips.
>
> I have found that most high performance 1/4 wave secondary coils
> make lousy driver secondary coils in the Tesla Magnifier. The
> reason is the impedance and inductance are too high, and the 1/4
> wave coil is not designed or constructed to handle high current
> outputs. 1/4 wave coils built per my instructions (posted here
> several times) are designed to produce excellent 1/4 wave voltage
> peaks, not 1/8th wave current. Your best bet is to wind a special
> coil for use as a driver. With this in mind what type of coil
> design would work best? Well my first decent driver coil was
> built for use as a 1/4 wave resonator, but it dropped into the
> role of a Magnifier driver without complaint; it had a nice low
> aspect ratio, and it was wound with heavy stranded wire...
>
> A good general purpose Magnifier secondary has a very low aspect
> ratio for good tight coupling over the entire winding length (say
> about 1.5:1). It is wound with heavy stranded insulated wire (say
> #18 or larger) to help carry heavy RF currents with lower losses.
> The frequency of the coil should not be too low, say in the area
> of 400 kHz for most medium systems.
>
> For the extra coil you want to pack a lot of inductance into a
> small unit volume, but not too much. You will end up with an
> amazingly short resonating coil if this is done properly. Use a
> 6" or 8" coil form with an aspect ratio a little over 2:1. For
> winding the coil use say #20 -#24 double Formvar magnet wire. The
> extra coil must be heavily top loaded with toroid discharger in
> order to produce really killer performance, as is the case when
> pumping a lot of energy through any magnet wire coil. The
> impedance in the bare extra coil must be higher than the driver
> coil by some margin, and the frequency of the extra coil should
> be brought down around 200 kHz by top loading the coil with
> discharger. The impedance of the driver must be low (heavy
> stranded wire spaced by insulation) while the impedance of the
> extra coil must be high (thin magnet wire, close wound turns)
>
> The tank circuit of the Magnifier must be tuned to the same
> frequency as the extra coil with discharger. Set the driver
> secondary inside the primary and run a transmission line some 6-
> 8' to the extra coil. The extra coil must be away from any
> field damping effects such as ground, large metal objects, other
> coils etc. It must be allowed to resonate as freely as possible.
>
>
>