Re: Primary Heating

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

Original poster: "Paul Nicholson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>

Hi All,

David Rieben wrote:
> I definitely have a good, solid low resistance ground connection
> fron the inner primary turn

Fair enough - had to be eliminated.

Bert wrote:
> Perhaps "current bunching" on the innermost turns (due to proximity
> effect?) so that these turns develop higher Joule heating? 

Well that sounds like the next best explanation.  I suppose I'm going
to have to write that program to plot the magnetic field. As a quick
look we can use acmi to show the distribution of self-induction
across the primary.  If this is divided by the area of each turn,
we end up with a set of numbers proportional to the B field strength
in the region of each turn [*]. Eg for a 12 turn primary, 5" inner, 
12" outer, see
 http://www.abelian.demon.co.uk/tmp/flat-pri-B.gif

Is that enough of a concentration in the center?  If the inner field
were say 5 times the outer field, does that mean the proximity loss
is 5 times higher in the inner turns?  It would only make a difference
to the heating of the inner turns if the proximity loss was 
significant (equal or greater than) compared with the straight line
AC resistance (ordinary skin-effect) loss.  I've no idea how to work
that out.

rheidlebaugh wrote:
> MY 4 PARRALEL DOUBLE STRAPED WITH 1" WIDE STRAPS 30 KV CAPACITORS
> ONLY PRODUCE SLOW CURRENT INPUT OF A SIGN WAVE WHEN MY SG FIRES.

Caps key stuck?  You seem very sure that your primary fails to obey
elementary circuit theory.  I wonder why?  Hmm, on second thoughts,
perhaps I'd better not ask.

[*] I've just thought, dividing by the area enclosed by each turn
just gives the average field within the given turn, so the actual
difference between inner and outer parts of the field may be a lot
higher than shown in the graph.  I'll just have find time to do
that program.
--
Paul Nicholson
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