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Re: Guide 60HzMatch



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> From: Tesla List <tesla-at-poodle.pupman-dot-com>
> To: Tesla-list-subscribers-at-poodle.pupman-dot-com
> Subject: Re: Guide 60HzMatch
> Date: Wednesday, January 29, 1997 11:10 PM
> 
> > Subject: Guide 60HzMatch
> 
> Subscriber: harris-at-parkave-dot-net Wed Jan 29 21:03:16 1997
> Date: Fri, 28 Feb 1997 17:11:59 -0500
> From: Ed Harris <harris-at-parkave-dot-net>
> To: tesla-at-pupman-dot-com
> Subject: Re: Guide 60HzMatch
> 
>     [The following text is in the "ISO-8859-1" character set]
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> 
> 
> > 
> > Subscriber: tom_mcgahee-at-sigmais-dot-com Tue Jan 28 22:58:51 1997
> > Date: Tue, 28 Jan 1997 15:40:47 -0500
> > From: Thomas McGahee <tom_mcgahee-at-sigmais-dot-com>
> > To: Tesla List <tesla-at-pupman-dot-com>
> > Subject: Guide 60HzMatch
> > Critique style, tone, syntax, grammar, but especially home in on
content,
> > useability, etc. For all I know, this may be totally wrong.
> > If you have ANY relevant material, please e-mail to me Re:Guide
> 60HzMatch.
> 
> Tom-
> 
> > The transformer secondary winding has a characteristic impedance at
> 50/60Hz
> > that will limit the maximum current that the transformer can deliver.
You
> > can model the transformer as a perfect voltage source in series with an
> > inductor and a resistor. The resistance is caused by
> > the length and diameter of wire used in the construction of the
> > transformer's secondary. The inductor represents the inductance of the
> > transformer secondary, which causes its AC resistance at 50/60Hz. {Fig
??
> > Eq ??}
> 
> I would have thought that the inductance in series with the resistor and
> voltage source would be indicative of the transformers "leakage"
inductance
> -not- the
> whole secondary inductance:  if a transformer with perfect coupling and
> zero
> resistance was connected to a perfect ac voltage source on the primary
side
> the secondary's output impedance would be zero.
> 

The use of Neon transformers makes this discussion a bit messy, because if
you really want to know, the darn things have these shunts that basically
cause a sort of current limiting effect. It's not like a textbook
transformer, I can tell you that! That's one reason why I am not really
sure how to handle the discussion. Are we trying to match the capacitive
reactance to the EFFECTIVE Output Impedance at rated current? Or are we
talking about some other impedance (as you said, the leakage inductance),
or maybe the inductance as seen by the primary.

None of the stuff I have read so far really explains that part of it.
That's why I said in my post of the article that I may have gotten this all
wrong. By wrong, I mean as regards to WHAT inductance it is that we really
have to match. If you know for sure or find out, please share that
information with me. I don't feel comfortable releasing this article until
I have a few points cleared up. I sure as heck don't want to confuse people
or give wrong information!!

Another issue is, IF it IS the leakage inductance, how does one quantify
this. As I said in my notes on the Guide, the only statement I could find
said that the transformer impedance was Etrans/Itrans. True enough, but
what Etrans? Emax? Etrans as measured AT Itrans? Wouldn't that be
significantly BELOW 12KV for a 12KV transformer, since the darn thing is
now running in current limit mode?

I need Input, DATA, More DATA!!!

> > 
> > Note: Do not confuse this 50/60Hz resonant frequency with the resonant
> > frequency of the RF portion of the Tank circuit, or the self-resonant
> > frequency of the secondary. 
> > 
> > 
> > Additional Remarks:
> > 
> > If RF chokes are introduced into the transformer circuit, then their
> > inductive reactance at 50/60Hz may have some effect on the total
> inductive
> > reactance, though it is generally small compared to the inductive
> reactance
> > of the transformer's secondary. 
> > 
> > The RF impedance of chokes does not enter into this
> > discussion of matching, because in matching we are only concerned with
> the
> > charge cycle, not the discharge cycle. 
> 
> Well, OK but I think it's worth mentioning that power/neon transformers
all
> have
> rather complicated behavior as a function of the frequency applied.

Tell me about it! That's what's driving me nuts! The few statements I see
about transformer/capacitor 60Hz coupling make it sound like you just write
down some numbers from the nameplate of your transformer, shove it into
some nice clean equation like R=E/I and come up with the right value for
the inductive reactance. But something in my gut tells me it ain't gonna be
that easy in Real Life, especially with a Neon transformer!

If I can't help people quantify such things, at least I want to tell them
WHY so that they can be wary in the proper places! Like, "HEY, why am I
getting these huge sparks over here in my Variac?? How can I stop this?"

> The
> seconday's
> impedance generally goes down rather significanly (1-2kOhm ) near the
tesla
> resonant frequency even though the secondary inductance is some number of
> Henries. The coupling between the primary and secondary is also a strong
> function of frequency and is almost neglible for telsa resonant
> frequencies.
> 

That is useful for understanding some of the Neon's failure modes.

> It would also be nice to include formulas (fairly common) for estimating
> transformer
> parameters like: maximum primary voltage allowed before core saturation,
> typical
> silicon steel permeability, and maybe the concept of reluctance.
> 

OK, are there any such published data for Neon transformers? You might
think that pole pigs would at least have such a thing... but most of these
guys with pole pigs ballast the primary to prevent excessive primary
currents. And they use neat things like arc welders in parallel with heater
elements as the ballast. Give me a nice formula for THAT! (Lemme see, now,
you multiply the maximum amps by the serial number, and then divide by pi
times the square root of the weight of the arc welder, then add 3 times the
wattage of the combined heater elements as a fudge factor. Yeah, that
oughta do it!)

But yes, the concepts of saturation, permeability, reluctance... these need
to be brought in to make the picture more complete.

> -Ed Harris

Ed, thanks again for you response. If you come up with any further stuff,
please let me know. This has to be a cooperative effort to succeed, and I
thank you for your cooperation. Keep in touch! When the next revision comes
out you will see that I included several things you discussed.

Fr. Tom McGahee