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Re: Ballasting ..... Again

In a message dated 10/22/98 9:22:45 PM Pacific Daylight Time, tesla-at-pupman-dot-com
writes:

<< 
 G'Day World,
 
 I've been a bit quiet of late ....... busy ...... winding ... winding ...
 winding .......
 
 My 5 kVA transformer is nearing completion.  Wound up using 0.71mm wire for
 the new secondary.  Needed 19 layers/winding to get 60:1 and 14.4 kV, but
 due to thickness of insulation etc the window will only allow 18 layers
 .... still, 13.6 kV will do just fine ;-)
 
 While I have lost a few volts, I suspect the heavier wire/insulation will
 pay for itself in the long run.
 
 Anyhow, I digress......
 
 The point of the post is to discuss ballasting this monster.  I have a 15A
 variac, which will limit me to 3.6 kV theoretically (though I could
 probably squeeze a little more for short runs).  I have a quantity of
 left-over wire from the primary (it had windings out to 440V - since
 removed) which I could use for an inductor with an appropriate core.  This
 wire is rectangular and about 3.5 x 2mm .... quite heavy !
 
 I have noted the multitude of posts on using welders (which I don't have
 .... but could acquire if required).  Also the debate on using/not-using
 series resistive elements.
 
 The local 'junk shoppe' has some 20A variacs which I could skuttle.  If I
 wound an inductive ballast on one of these how many turns would I need for
 say 5, 10, 15, 20A steps ??
 
 I also noted with *great interest* the comments suggesting no difference in
 performance with slotted vs non-slotted cores - obviously not having to cut
 the core would save a lot of effort.
 
 I want to GET THIS RIGHT .......... having spent many hours winding this
 toy, I don't want to see it go up in smoke !!
 
 Thoughts, advice etc welcomed.
 
 Cheers,
 
 
 Mark >>

Mark,

Good job on the home made transformer.  Maybe you could go into business
making these for all of us:)  I agree with D.C. Cox, you want somewhere in the
neighborhood of 10 to 30 mh of inductance.  I use a 5000 watt variac rated at
41 amps and did not cut the core - although I think it needs to be cut because
I can here it groaning and believe it is very close to saturation.  I am only
using about one half of it and running at about 35 amps.  I also use 3.2 ohms
of series resistance and would suggest you start with some and try different
combinations of inductance and resistance to get the control that you want.

Ed Sonderman