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Re: Neon power draw, and resonant stresses.
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Monday, September 01, 1997 6:18 PM
To: Tesla List
Subject: Re: Neon power draw, and resonant stresses.
Tesla List wrote:
>
> From: Mad Coiler[SMTP:tesla_coiler-at-hotmail-dot-com]
> Sent: Friday, August 29, 1997 11:43 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Re[2]: Neon power draw, and resonant stresses.
>
> >From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
> >Sent: Friday, August 29, 1997 4:22 AM
> >To: tesla-at-pupman-dot-com
> >Subject: Re: Re[2]: Neon power draw, and resonant stresses.
> >
> >In a message dated 97-08-28 15:56:55 EDT, you write:
> >
> ><<
> >> John, you have brought up an issue I had asked the list about and
> never
> >> got a response. You say "If it's value is such that it resonates
> with
> >> the leakage reactance of the neon trannie..." How is this determined.
> In
> >> the designing phase how could one determine if this would happen? And
> >> does this stress the neon two much, or is it ok as long as the gap
> fires
> >> to discharge it?
> >
> >> Still resonating in Ohio,
> >> Mad Coiler
> >> >>
> >
> >Mad,
> >
> >I'm unable to find the formula, I was hoping someone would re-post
> >it for you again. "does it stress the neon too much?"... depends on
> >what you mean by too much. Certainly, it stresses it more than
> >without resonant charging. Yes, by limiting the gap spacing, you can
> >limit the voltage across the trannie, and still obtain the benefit of
> >the increased current draw. None of my neons have yet burned,
> >and I've been using this resonant method for years.
> >(I did burn out a couple of neons...but that was when I used a
> >non-sync rotary gap!)
> >
> >John Freau
> >
> >
>
> John, when I asked about the stressing thing my only concern is about
> the neon - i mean will it eventually damage it. I see you haven't had
> any problems burning up neons with this so you have answered my question
> about that. But about figuring the C for 60Hz resonance...
>
> Mad Coiler
Mad Coiler and all,
You'll achieve low frequency resonance when the inductive reactance of
your neon(s) is "neutralized" by the capacitive reactance of your tank
cap. For 15 KV neons, this works out to be just around 0.01 uF for every
60 MA of current if you are running off a 60 Hz power source. The tank
capacitance will need to be about 20% higher if you run off a 50 Hz
power source.
For example, suppose your neon is a 15 KV 60 MA. It's effective output
short-circuit impedance is:
XL = 15000/0.060 = 250,000 Ohms (reactive).
At an incoming line frequency F, your tank capacitor's capacitive
reactance will be:
XC = 1,000,000/(2*Pi*F*C) Ohms, where C is in uF
Setting XL = XC, and solving for C:
C = I/(V2*Pi*F)
where:
I = total sum of faceplate ratings of neon bank in MilliAmps
V = faceplate RMS in Kilovolt for neon bank
F = Incoming Line Frequency in Hz
Pi = 3.14159
C = in uFarad
C = 60/(15*6.28*60) = 60/11,304
= 0.0106 uF
By plugging in the output RMS voltage and current for the neon
transformer (or bank of neon transformers), you can solve for the
appropriate tank cap value. Since this seems to be a question that comes
up fairly often, I've generated the tables below for 9, 12 and 15 KV
neons banks for both 60 and 50 Hz sources for typical low and medium
power ranges. Since the "Q" of the neon-cap LC circuit is fairly low
(5-10 typically), if you're within about 15% of the ideal tank
capacitance you'll encounter resonance effects. For example, the point
at which the spark gap JUST begins to fire intermittently will be
reached at a relatively low variac setting (about 15% on my system).
Remember to keep your gap distances reasonable to avoid overvolting your
transformers or tank caps(!), and don't attempt to run the system with
an asynchronous rotary gap.
Bank (uF) (uF)
Current 60 Hz 50 Hz
-at- 15 KV: Tank Cap: Tank Cap:
======= ========= =========
30 MA 0.005 0.006
60 MA 0.011 0.013
90 MA 0.016 0.019
120 MA 0.021 0.026
150 MA 0.027 0.032
180 MA 0.032 0.038
Bank (uF) (uF)
Current 60 Hz 50 Hz
-at- 12 KV: Tank Cap: Tank Cap:
========= ========= =========
30 MA 0.006 0.008
60 MA 0.013 0.016
90 MA 0.020 0.024
120 MA 0.027 0.032
150 MA 0.033 0.040
180 MA 0.032 0.048
Bank (uF) (uF)
Current 60 Hz 50 Hz
-at- 9 KV: Tank Cap: Tank Cap:
======== ========= =========
30 MA 0.009 0.011
60 MA 0.018 0.021
90 MA 0.027 0.032
120 MA 0.035 0.042
150 MA 0.044 0.053
180 MA 0.053 0.064
Hope this helps!
-- Bert H --