Re: New idea for TC Primary

From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Wednesday, July 16, 1997 5:31 PM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: New idea for TC Primary

Hello all,
             I missed the original of this post and a few others when 
the list went down I suspect.

 Date forwarded: Tue, 15 Jul 1997 22:18:20 -0600
To:             "'Tesla List'" <tesla-at-poodle.pupman-dot-com>
Subject:        Re: New idea for TC Primary
Date sent:      Tue, 15 Jul 1997 23:00:37 -0500
Forwarded by:   tesla-at-pupman-dot-com
From:           Tesla List <tesla-at-pupman-dot-com>

From:   FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
Sent:   Tuesday, July 15, 1997 9:45 AM
To:     tesla-at-pupman-dot-com
Subject:    Re: New idea for TC Primary

In a message dated 97-07-15 03:09:05 EDT, you write:

<< After the recent discussions on the 30vs 60mA neons, It seems to me that
> an AC Tesla's primary circuit is basically a no win situation with
> regards to power efficiency. You have to provide inductive balasting, or
> current limited Xformers to be able to quench the gap after the gap
> fires but then you are limited by this inductance as to how fast you can
> re-charge your cap and this in turn limits your maximum breaks/sec.

JF comments:


If the amount of inductive ballasting is chosen correctly, its reactance
will be "neutralized" by the reactance of the tank capacitor, and there 
will be NO effective inductive current limiting, while the caps are charging,
but there will still be current limiting after the gap fires which reduces 
losses at that time.  So actually all is well. 

>Also as the AC cycle reverses, whatever charge the cap already 
>has is wasted, as it must discharge before it can start to charge 
>with the opposite polarity for the next few breaks.


If a 120 Hz (100Hz) break rate is used, along with resonant charging,
there will be a large phase shift of the voltage, which will cause the
capacitor to reach peak charge, and fire, just as the input AC is at
the zero-crossing point.  Thus there is no wasted charging.  At higher
break rates, this benefit is at least partially lost it would seem?
> With this in mind, I propose the following system. A pole pig or even
> Microwave oven transformers and voltage doublers, are used to produce
> around 10Kv DC. (in this mode of operation, they should be reasonably
> efficient). This is used to charge some fairly beefy caps, say around
> 1uF. The output of this supply is connected to a standard TC primary
> circuit but via a special, two stage rotary gap as follows
>       Commutator    Discharge
>          Gap         Gap
> ----------* *--------* *---------
> +                  |             \
>                    |             /
> High current      --- Pulse      \ TC
> DC Supply         --- Cap        / Primary
 >                   |             \
 >                   |             /
> ---------------------------------
> The Gaps consist of a motorized plexiglass disk with a Cylinder of brass
> with four notches on the inside, say 4" diam (commutator gap) and a ring
> of bolts on the outside lined up with the notches, say 6" diameter
> (normal gap). The gaps are arranged so that when the normal gap on the
> outside lines up with its discharge terminals, the comutator gap breaks
> the flow of current due to the notch. The commutator gap must be set up
> with fairly fine tolerances.
> The basic idea is to allow the pulse cap to charge up via the commutator
> and then discharge via the normal gap. The commutator will allow the cap
> to charge very rapidly, as there is no inductive limiting from the
> supply filter caps, and then the normal gap will allow the cap to
> discharge and quench rapidly as, at that moment, the supply is
> disconnected. Theoretically, the number of breaks per second should only
> be limited by the DC supply current and the size of the primary cap. The
> primary cap could be kept fairly small and the system run at very high
> BPS.
> Has anyone heard of, or tried this idea? The gap should be fairly easy
> to build for you guys that have lathes, unfortunately I am not in this
> category yet. Please send me flames or otherwise as I intend to try the
> idea as soon as I collect enough parts.

MW comments: I also thought of this several years ago. I put out a 
query on the scheme and got a reply from Mark Barton who had tried it
at around 10 - 20 kVA. I quote:

     " We got kickbacks, the likes of which I've never seen. We even 
popped 100W lightbulbs in a neighbour's house".

    I had a brief discussion offlist with Mark on this. He thought 
it may have to do with connecting a partially charged cap back onto 
the mains. My idea is that connecting a cap, charged or not back to 
the mains at an unfavourable part of the mains cycle is throwing a 
near dead short back across the mains. I dropped the idea for use
of the standard transformer/choke setup. However, if zero-voltage 
switching on the primary side could be implemented, I see no reason 
why it wouldn't be just fine. However, the scheme is necessarily 
reduced to using a synchronous firing circuit because of the zero-
crossing dilemma.
      My original idea was to be discharging one cap in the primary
while charging an alternate from the mains. As usual, normal timing
associated with energy transfer from TC primary to secondary renders
that idea somewhat superfluous to using a single cap.