On Mon, 29 Nov 2004 01:44:30 +0200, "Risto Tiilikainen"
wrote:

Can we consider a standard car ignition coil a Tesla coil ? A cheap,
reliable and simple one.
There is primary with capacitor in distributor and secondary with self
resonance of course.
Good high voltage insulation is achieved with coil in oil bath .

A car ignition coil isn't tuned primary to secondary - Frequency is
much lower than all but the largest tesla coils. Most Tesla coils are
air-core transformers. Induction coils seldom put out the voltage of
tesla coils. A moderate TC can output 100,000 volts compared to
20,000 for a car ignition coil. 250,000 volts isn't hard to get out
of a TC.


Can we consider TV line transformer a Tesla coil or purely a transformer ?
It is produced to resonate in selected line frequency

Flyback transformers have some of the characteristics of TC's, but
usually much lower voltage, and their frequency is lower. I don't
believe they are resonant - but don't know for a fact. Secondary
isn't series resonant. A color CRT may go up to 50,000 volts.

I wonder how is normal neon light high tension generated.

They used to use current limited (magnetic shunt) line frequency
transformers that relied on turns ratio to step up the voltage. Most
of them still do use this type of transformer. When the gas in the
tube ionizes the current limiting of the transformer protects the
transformer.

Do they use some kind simple tesla coil system to ionize the rare cas inside
the glastubing or are they using choke like normal fluorescent tubes.

The more modern neon sign systems do use high frequency/ high voltage
generators because they are cheaper, smaller, lighter, and safer.

In any case neon lights seem to be safe for public with very simple
construction.

Neon signs and neon sign transformers aren't all that safe. Many are
current limited below the ~100 ma necessary to kill (but 100 ma is
just a number; they didn't arrive at it empirically . . .) Look at
the controversy surrounding taser weapons - much lower average current
and power than a NST.

Safety protection with fluorescent lights is much and more complicated and
failsafe.

The ordinary magnetic ballast fluorescent lamps have the usual line
voltage hazards. I wouldn't consider them any safer than incandescent
lamps.

High frequency fluorescent lamps may be somewhat better - but the one
I just took apart does not have line voltage isolation. Looks like
they just rectify the AC line than chop it at a high frequency and use
a small choke to limit current.

Fail safe? How do you figure?

New questions made Risto; OH2BT

Fail safe? How do you figure?

Thanks for your comments to the various questions.

Maybe my English impression was poor.
With fail safe I was meaning the safe construction which is controlled by
regulations and paragraphs.
In outdoor use and in moist places standard fluorescent tubes, their wiring,
chokes and igniter are never allowed to have open construction. (at least
here in Nordic countries)
Similar situation is not with neon lights on the walls. Sometimes there are
bare without any enclosures.
I even remember having seen the end wires of the tubes visible.
Well - normally neon lights are rather high so that people cannot touch
them.

Risto

On Thu, 2 Dec 2004 00:27:15 +0200, "Risto Tiilikainen"
wrote:



Fail safe? How do you figure?

Thanks for your comments to the various questions.

Maybe my English impression was poor.
With fail safe I was meaning the safe construction which is controlled by
regulations and paragraphs.
In outdoor use and in moist places standard fluorescent tubes, their wiring,
chokes and igniter are never allowed to have open construction. (at least
here in Nordic countries)
Similar situation is not with neon lights on the walls. Sometimes there are
bare without any enclosures.
I even remember having seen the end wires of the tubes visible.
Well - normally neon lights are rather high so that people cannot touch
them.

Risto

Interesting. I'd probably call what you refer to as "fail safe" as
"foolproof."

Do you have stricter regulations regarding fluorescent lamps versus
other line operated electrical appliances?

Perhaps the reason for stricter controls is the fact that fluorescent
lamps are frequently used in family residences.

Or, perhaps they are concerned about electromagnetic fields - here it
is politically unpopular to even hint that low frequency emf's can be
damaging to health. I've read that some Scandinavian countries are
considering imposing LF EMF limits or are already doing so. Do you
know anything about that?

I see the same things with neon tubes here, particularly in the older
establishments. Wires with just a plastic or glass sleeve over the
connection to the tubes and not protected from water or hands.

The transformers usually have a secondary center tap that is grounded,
so each side of the neon tube only sees half the total high voltage.
But half is still a lot . . . My smaller transformer is 10 KV @ 30 ma
(for ignition on an oil furnace - but identical in construction to a
NST). I can't imagine it feels good if one were to get body parts
across it. It is designed to start fires . . . I'm not about to try
it and I don't know anyone who got shocked by one.

One correction to my earlier post: The common style of car ignition
transformer relies on a rapidly collapsing magnetic field to produce a
spike of high voltage, not just the turns ratio. Field builds slowly
and collapses fast.

If the same induction coil were used with a capacitive discharge
ignition circuit, the turns ratio and high primary voltage produces
the high voltage.