Re: tesla coil is an air core. why?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Brian by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ka1bbg-at-webryders-dot-net>

I made a secondary coil without a form so called. i used frozen wax,turned
it on a lathe,wound a coil over it with a thin layer of Saran wrap,wound the
coil and when thawed i gave it a coat of thin epoxy. once the epoxy set i
dunked it into boiling hot water untill the wax melted,pulled the saran wrap
off. coil was naked of form except for a very thin layer of epoxy. i coated
the inside with 1 thin layer of epoxy. the coil worked fine till i put the
power to it,then sparks jumped on the inside across the windings almost as
if no insulation was there. i put a piece of pvc pipe inside and that cured
the sparking problem but i now had a coil with pvc support-so to speak. The
coil was destroyed when the cat knocked it off the bench...one could call it
a fragile experience. cul brian f.
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, August 08, 2002 1:35 PM
Subject: Re: tesla coil is an air core. why?


> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>
>
>
> > why does the tesla coil use an air cored design?
> Short answer:
>
> Because that's what works best, so far.
>
>   Tesla started with cored coils.  With the materials
>
> available, he found that air core (no core) worked
> best.  I'd guess new materials (except maybe
> ferrite) have not changed this.
>
>
> > I thought of a few reasons, but wasn't sure if i was right.
>
> > core materials can have hysteresis losses, eddy current losses,
>
> > problems with saturation, and poor high frequency response.
> > therefore air cores are better?
>
> yes yes yes and yes.
> (unless i lost count....)
> ALSO a metal core tends to be tricky to manage
> around Really High Voltages.
>
>
> > I'm guessing that if you used a core the coil would loose
>
> > considerable efficiency or fail to oscillate (since the
>
> > core would increase the  inductance.)
>
> It could be readjusted.
>
>
> > but what if you used a diamagnetic material as a core.
>
> I can't think why?
> 'core' has two reasons:
> physically support the windings:
> HDPE, cardboard, etc do nicely.
> Concentrate the magnetic fields, reducing stray
> fields and device size.
> Since size is of less importance than
> avoiding losses (which are lowish anyway)
>
> and avoiding sparks to core are critical,
> no core (in the magnetic sense) is used.
>
> There was some discussion of a ferrite core
> secondary.  Could someone summarize?
> -
> best
> dwp
>
> ...the net of a million lies...
> Vernor Vinge
> There are Many Web Sites which Say Many Things.
> -me
>
>
>
>