Re: 1st Motorized Spark Gap!

To: tesla-at-pupman-dot-com
Subject: Re: 1st Motorized Spark Gap!
From: Jim Fosse <jim.fosse-at-bdt-dot-com>
Date: Tue, 22 Oct 1996 02:22:07 GMT

>> 2) Is there a certain speed-range that most of you find works best? I
>> realize that speed probably affects tuning, but what would be considered
>> to slow or to fast?
>
>That depends entirely on the charging characteristics of the power 
>supply (which includes the transformer, chokes, and primary cap). For 
>example, a large limiting inductor charges a given capacitor much 
>more slowly than a small inductor. This is really a can of worms for 
>a simple explanation. 

Watch out for the ballast inductance of your primary system resonating
with the TC primary cap at the break rate of your rotary. If this
occurs, the TC primary cap will be charged to a much higher voltage
that simple transformer action will account for.  Using this method, I
taken 220V into my ballast inductor, run it through my pole pig, and
have gotten 85kV out (of a 7.2kV pig overdriven 2:1), which proceded
to punch holes in my rolled cap built with 0.120" of polyethylene.

>The cap, if not hindered by a high break rate, 
>will charge to a voltage allowed by inductor energy storage which is
>dependent on inductance and peak current according to 0.5LI^2 (cap can
>reach :  Vcap = Ipk*SQRT(L/C) assuming no additional transformer push 
>behind it - usually not the case). You can see from this that varying
>break rate can seriously influence cap voltage assuming significant
>energy storage in the inductor. Greg Leyh used this to good effect in
>his big coil which I recommend anyone interested in issues surrounding
>the use of rotaries and resonant charging get a hold of.
>
>Malcolm
>
	jim