Re: Current Limiting and Impedence

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Bob (R.A.) Jones" <a1accounting@xxxxxxxxxxxxx>


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Saturday, May 07, 2005 7:50 AM
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.

I don't like your analogy it does not work for me.
I would describe a gapless core as putting up a very strong resistance with 
a big back emf for small current i.e. a very stiff spring.
But if you compress it too much it suddenly turns in to noodles.
Its air that's noodle like.  It puts up thousands of times less  resistance 
(back emf) but never stops resisting you.

So if your pongo stick was the same as a gap less core would work just fine 
if the displacement was small as it would be good stiff spring but if you 
bounced too hard it would turn in to a weak noodle spring.

Robert (R. A.) Jones
A1 Accounting, Inc., Fl
407 649 6400