RE: Primary Heating

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Hi David:

Thank you for sharing the observation that your primary heating is also
most evident on the innermost turns; I was beginning to think that I was
the only one to have seen this!  As far as your suggestion that the current
is greatest at the inside because the V & I are 90 degrees out of phase,
this is true.  However, the current must be the same through all parts of
the primary, unless some is "leaking" out somewhere along the way, which is
why I suggested corona.

Regards, Gary Lau
MA, USA




Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Tesla729-at-cs-dot-com>

Hey all, 

There has already been some discussion on this thread but I just
thought of something that I could add. My 10 kVA pole pig coil 
uses 5/8" copper tubing as the primary and even a conductor this 
robust does heat up if I run the coil for more than a minute or so.
Like someone else mentioned though, most of the heating is con-
fined to the 2 innermost turns. My primary cap is 82 nFD, so at 
around 20 kV peak (14000 X 1.41) that should figure to around 
16 Joules per bang, if my math is right. Of course, since I'm run-
ning asynchronous RSG on standard AC in the 300 to 350 BPS
range, I'm sure that not every bang is going to occur at or near the 
sine wave peak, so the average Joules/ bang may be closer to the 
10 Joule range (just a guess, though). Anyway, evidently these
peak currents are substantial to be able to noticably heat up 5/8"
tubing. And my guess on why most of the heating is confined to
the inner-most primary turns is that the current max always oc-
curs at the grounded end as opposed to the voltage max, which 
occurs at the "hot" end (V and I are running 90* out of phase, I think).
Of course a pole pig system is going to be running considerably
more power than an NST system, too, so I'm sure primary heating
would be more noticable in a piggie system ;-)

Just my very uneducated opinion ;-)

Coiling in Memphis,
David Rieben