Re: Primary Heating

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

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

As I read this subject I see current is every where the same. No current is
not every where the same. Yes it is a series circuit, but the load is not
all places the same. The load is distributed in a log distrabution into the
secondary and surounding areas and across the resonant length of the primary
starting at 22 ohms to over 6oo meg at the 1/4 wave resinant point at the
moment of time of firing. Yes the average current is low, but the
instantanious current is often well over 400 amps traveling as a slow movind
standing wave pulse along the conductor decresing as the impedance
increases. Keeping in mind in a TC we are not dealing with a uniform sign
wave current, but a multi harmonic pulse burst of intense current. The
heating effect of 400 amps in 22 ohms is more than 40ua in 600meg.This is
just my minds view of what should be happening in the primary.AMATURE RADIO
OPERATORS HAVE FOUND IT NESSISARY to use larger tubing at the feed point of
an antenna to carry the input power.
  Robert  H 

> From: "Tesla list" <tesla-at-pupman-dot-com>
> Date: Mon, 04 Mar 2002 20:46:59 -0700
> To: tesla-at-pupman-dot-com
> Subject: Re: Primary Heating
> Resent-From: tesla-at-pupman-dot-com
> Resent-Date: Mon, 4 Mar 2002 21:15:20 -0700
> 
> Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <bert.hickman-at-aquila-dot-net>
> 
> All,
> 
> Hmm... I've also seen this after extended runs. Perhaps "current
> bunching" on the innermost turns (due to proximity effect?) so that
> these turns develop higher Joule heating?
> 
> -- Bert --
> -- 
> Bert Hickman
> Stoneridge Engineering
> Coins Shrunk Electromagnetically!
> http://www.teslamania-dot-com
> 
> Tesla list wrote:
>> 
>> Original poster: "Paul Nicholson by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <paul-at-abelian.demon.co.uk>
>> 
>> David Rieben wrote:
>> 
>>> most of the heating is confined to the 2 innermost turns
>> 
>> and others have reported similarly.  Wonder why.  We can exclude
>> a localised current max in the primary at the operating frequency
>> because the self-cap of the primary is very small compared with
>> the added parallel cap of the primary tank, eg 100pF/82nF < 1%, so
>> that the primary current is virtually uniform [*].
>> 
>> David, do you have a good low-resistance connection at the inner
>> end of the primary?  Perhaps you can run some 60Hz AC current through
>> the primary and see if the localised heating still occurs.
>> 
>> If a 60Hz current doesn't reveal the same localised hot spot, then
>> we might have to look for sources of HF.
>> 
>>> the current max always occurs at the grounded end as opposed to
>> 
>> We expect uniform current in the primary at Fres.  But if higher
>> frequency energy is being developed in the coil anywhere (parasitic
>> resonance involving the gap, secondary arcs redistributing mode
>> energy, etc) then it could be interesting.
>> 
>>> (V and I are running 90* out of phase, I think).
>> 
>> Yes, I lags V by 90 degrees.
>> 
>> First, we should eliminate the simplest explanation - lossy connection
>> to primary inner, or heat from the gap conducting through to the
>> primary.
>> 
>> [*] providing we ignore the capacitance between primary and
>> secondary.  This can be quite high for the inner-most turns, and
>> the resulting displacement current adds a non-uniform component to
>> the primary current.  But this component can never exceed the coil
>> base current (if sec base is properly grounded), so therefore this
>> non-uniform component of Ipri must be less than the main primary
>> current by at least the factor sqrt(Csec/Cpri).
>> --
>> Paul Nicholson
>> --
> 
> 
>