Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Chuck" <g0mdk@xxxxxxxxxxxxx>

I had acquired a 10kV 300mA (rated) low Z type equiv. to a pole pig. I 
needed a ballast to use it with my coil and rotary spark gap. As a 
consequence I looked into the theory of such an arrangement (ballast in 
series with the primary of the transformer. Not able to find one I designed 
and built one. I found it so fascinating that I put up a page on my web 
site describing one. Most of my stuff there is pretty consistent with 
inputs to this thread. Please have a look: 
http://myweb.tiscali.co.uk/teslatutorial/ballast.htm  Unfortunately my eye 
sight has diminished to where me and HV have parted company before we got 
into any arguments. That explains the unfinished part of the page, but it 
still may be informative and helpful to some.

Cheers

Chuck


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, May 07, 2005 3:50 PM
Subject: Re: Current Limiting and Impedence


> Original poster: Steve Conner <steve@xxxxxxxxxxxx>
>
>
> > Original poster: "Gerald  Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
> >
> > Could you elaborate a little more on the lack of an air gap.
>
> Ballast inductors don't work without air gaps. That's just the way the 
> world is. If you think you have a gap-less ballast working, it's probably 
> behaving as a saturable reactor.
>
> If you go back in the archives you'll find this topic discussed in a lot 
> more technical detail by me and many others. But for a more seat of the 
> pants explanation-
>
> A ballast inductor is like a spring in that it stores energy. The resonant 
> charging process in Tesla coils (whether running off AC or DC) is rather 
> like a spring being compressed when the gap fires, and as it bounces back 
> it shoots the tank capacitor to an even higher voltage than the supply. 
> It's sort of like an electrical pogo stick.
>
> Iron cores are not good at storing energy because they magnetise too 
> easily. It only takes a very little H to make a lot of B. To take the 
> spring analogy, a gapless iron cored inductor would be like a spring made 
> of some weak floppy substance such as noodles. As soon as you put a 
> voltage across it, it barely puts up a fight (hardly any current flows) 
> and then before it has stored any worthwhile energy it bottoms out 
> (saturates because B got too big) and looks like a short circuit.
>
> This kind of behaviour is fine in a transformer where you want the 
> magnetizing inductance to draw as little current, and store as little 
> energy as possible. But in a ballast, where you are trying to store 
> energy, it's about as effective as a pogo stick made of noodles.
>
> Putting the air gap in introduces a substance that doesn't magnetise so 
> easily. It's like upgrading from a noodle spring to a steel one, and you 
> go bouncing happily down the road.
>
>
> Steve Conner