RE: [TCML] Ballastwith adjustable Core

["Terry Oxandale" <Toxandale@xxxxxxx>]

One thing I found helpful was several pounds of 1/16" steel welding rod
with a thin external flux. The flux acts to insulate the individual
rods. I bundled these rods, as Richard describes, into a PVC tube with
caps on each end (and with epoxy poured into the tube to keep the rods
from vibrating and knocking the flux off the rods). It provided the core
I needed, but remained cool.

(un)Terry

-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Richard Quick
Sent: Wednesday, June 25, 2008 12:59 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Ballastwith adjustable Core

> First thing, yeah, it's not laminated. Will eddy currents be a
problem? 

Yes, you are designing a 60 cycle induction heater to heat treat or melt
a 3" x 12" iron slug.
 
> Second thing, assuming the above works, would the changes in
inductance be linear as I slide the coil in and out? Is there a formula
I can use for inductors with slugs? It's kind of not worth it if the
coil goes from half power to full blast with an inch of slug movement.

If the core were laminated, you would get a linear control as the core
is moved in and out of the coil.  What you probably want is some #14
soft iron wire that is coated with a thin layer of insulation such as
polyurethane, cut it into 12 inch sections, and bound up into to a
cylinder core. Works for me, though it will still heat some (it's pretty
small)... I built a larger core of this type.

Richard
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