RE- Safety Gap
From: Robert Michaels[SMTP:robert.michaels-at-online.sme-dot-org]
Sent: Thursday, November 20, 1997 11:31 AM
Subject: RE- Safety Gap
TL>To: Tesla List
TL>Subject: Re: RE- Safety Gap
TL>Thanks for the response Robert but I don't think you have answered my
TL>question. As I implied in my question I understand the action of the
[ ... ]
Oh? So I get another opportunity to insult your intelligence
perhaps from a new perspective?
Before I take swing at it permit me to get on my soap box
| Gentlemen (and the rest of you as well): |
| =Before= you attempt Tesla-coiling, get |
| get yourself to a bookstore or library and |
| get yourself a good book on physics and a |
| good book on electrical theory. |
| Tesla coiling is dangerous. It's all the |
| more so if done in ignorance. If you kill |
| yourself it's your business. If you injure |
| those around you, bring unfavorable attention |
| to the fraternity and encourage |
| the interest of regulatory and enforcement |
| authorities it becomes the business and the |
| burden of all of us. |
Thanks Vivian - I needed that. Now --
TL>inductors in protecting the transformer by their effect at 200Khz rather
TL>than 60Hz (50 in my case). But I am trying to understand where this extra
TL>voltage that exceeds the neon output is coming from or more particularly,
TL>requires extra protection.
At resonance, voltages are developed in the resonant circuit
which can exceed the supply voltage. This is a fundamental
principal of physics.
It is not unusual for those voltages to reach 4 or 5 times
the supply voltage. Thus, in a Tesla primary fed by a 10-kv.
transformer (neon or otherwise), resonant voltages of 40-kv.
are quite possible.
- - - - - - -
In the particular case of a neon transformer, it is also possi-
ble for the capacitor in the Tesla primary to achieve 60-Hz.
resonance with the inductance of the neon secondary.
Indeed, some workers in the field specifically chose the
capacitor to be resonant with the neon secondary.
Well! This creates a double indemnity: high resonant voltages
from the neon secondary, =and= from the Tesla primary!
- - - - - - -
Note -- in a practical circuit it is not necessary to be on
resonance to get voltage rises. The voltage =starts= going
up as resonance is approached. It =peaks= at resonance.
Thus, a capacitor which approximates resonance with a neon
secondary can cause dangerous (to the neon) voltages to be
[ ... ]
TL>in the tank. But when the gap ceases to conduct the primary acts as an open
TL>ended resonator. Hopefully this energy goes into the secondary, but if not,
TL>would create its own emf in the primary which may cause the gap to fire
TL>again but under its own steam. This may account for the different sounds
[ ... ]
I don't quite follow your argument here. It seems you are
mixing single-shot (or pulse) concepts with those of continuous
In single-pulse operation the gap fires several times until
the wave finally damps out.
In continuous operation, the gap fires every single time the
voltage across it is high enough to create a conductive path.
In an ac Tesla coil this is a =very= complex matter because
there is 60-Hz ac (50-Hz to you), plus high-frequency ac, plus
sidebands from intermodulation of the high-frequency/60-Hz,
plus higher-frequency components associated with fast-rise time
TL>I can understand the inductors might ring but it seems to me that the extra
TL>gap is basically their because the choke protection is not very good.
The chokes may ring or not. It's largely irrelevant to
The "extra gap" (if you mean the safety gap or gaps at the
neon transformer) protects the neon transformer (and the ac
line) from the above mentioned higher-than-nameplate voltages.
BTW -- there is nothing "extra" (as in the sense of
extraneous) about the safety gap. It is essential
to protect the transformer, and to protect the ac
line. It's like calling the safety valve on a
high-pressure boiler an "extra-neous valve".
TL>So from someone who has some electrical knowledge but is not afraid of
TL>asking dumb questions (to see if the answer is not obvious) > you say
We are all born dumb. We are doomed to remain so until
we start asking questions. Ignorance is no sin. Plunging
ahead blindly in the face of it is.
TL>"the slightly wider safety gap establishes an upper gap-limit for the
TL>system, in case you get a bit too frisky with the main gap"
TL>Does this mean a neon cannot be operated open circuit without risk of its
TL>insulation breaking down. The reason I ask is, can I set a safety gap with
TL>no load on the neon so it just doesn't fire. That way I can open my main
TL>gap to Max without worrying about tweaking two gaps.
Neons can be operated open circuit with impunity if the primary
voltage is increased/decreased gradually by means of a Variac
or the like. Switching the ac full-on full-off is inadvisable
as transients in excess of the secondary rating can easily be
produced. More to the point and purpose, such transients can
fire the safety gap one is trying to set. This creates the
impression the gap is too narrow, leading one to open the
gap further than it should be for good protection.
Go read those books!
Off to the library
myself -- in Detroit,USA