Re: Ballasting ..... the never-ending thread ;-)

To: tesla-at-pupman-dot-com
Subject: Re: Ballasting ..... the never-ending thread ;-)
From: Esondrmn-at-aol-dot-com (by way of "Terry Fritz (moderator)" <twf-at-verinet-dot-com>)
Date: Fri, 04 Dec 1998 16:28:18 -0700
Approved: twf-at-verinet-dot-com

In a message dated 12/3/98 2:58:07 PM Pacific Standard Time, tesla-at-pupman-dot-com
writes:

<< 
 >I'm intending to take this idea one step further by using a variable 
 >reluctance coil. I have constructed two "cores" , both heavily gapped 
 >internally by recovering 3C8x ferrite cores from old computer SMPS, 
 >smashing them to bits and stuffing the chips into PVC and acrylic 
 >piping. The largest of the two is about a foot long, 4.5" diameter 
 >and weighs a bundle and has an Al value somewhere around 300nH/turn^2 
 >if memory serves. By sliding this core in and out of a modest winding 
 >I have a variable inductance. This might also be useful for adjustable
 >primary ballasting with a stiff power transformer. The power losses 
 >should be considerably less than the gap. I did experimentally check a 
 >primary with one of these cores for losses and it looked better on 
 >the scope than an equivalent inductance and much larger air wound 
 >primary, gap included.

 Now this has me somewhat inspired.  I had ballasted my HBP (home-brew pig)
 with my neighbours welder plus some series R elements with initial success.

 Just bought a new house and am moving end of January, so coilin' takes a
 back seat for a while (but it does have a work-shop ).  Problem
 is my new neighbour is very unlikely to have a spare welder ...... so back
 to the drawing board :-(

 My second-favourite junk shop has *lots* of ferrite rods going cheap.  Lets
 say we fill a 4" PVC pipe with these & set the lot in epoxy resin, allowing
 a 1cm channel though the middle to take a threaded rod for position
 adjustment.

 1.  How long will I need to make the core ?

 2.  How many turns & what guage wire ?

 Given my aims are to limit current over the range 5-35 amps (more likely
 10-30A), with primary mains at 240V/50Hz.

 Thinking further.  Could we make it whole set-up shorter by using several
 winding layers, or would heat dissipation be a problem ?

 cheers

 Mark
  >>

We have discussed this a couple of times in past years.  I would like to see
someone build one of these.  We had established a desireable range of
inductance to be 5 to 25 mh, which covers the range of at least one welder
that was measured by Scott Myers (22.4 mh to 8.2 mh) - by the way, where is
Scott?

Ed Sonderman