[Prev][Next][Index][Thread]

RE- RF Chokes (fwd)





---------- Forwarded message ----------
Date: Tue, 25 Nov 1997 07:24:00 GMT
From: Robert Michaels <robert.michaels-at-online.sme-dot-org>
To: tesla-at-pupman-dot-com
Subject: RE- RF Chokes

TL>From:  Andrew Chin[SMTP:chinny-at-ozemail-dot-com.au]
TL>Subject:  RF Chokes

TL>Hey all.

        Hey, Chin,

TL>In an effort to protect neon trannies from RF, chokes are placed on the
TL>secondary line of the neon.  What I would like to know is what

        50% of your thinking is half right...

        The rf chokes also protect the ac line from ... rf.  Ideally
        there ought to be chokes in the primary as well.

                Or for those with more social responsibility
                (not to say fondness for their stereo, computer,
                cordless phone, etc.) -- a full-blown line filter.


        Those who use welding transformers in the primary (of pole
        pigs) accomplish this purpose, ipso facto.

        Those who place a power-factor correction capacitor in a
        neon transformer primary circuit likewise inherit some rf
        protection for the ac line.


TL>frequencies are we supposed to be stopping reaching the neon?  RF as far
TL>as I can recall ranges from about 300kHz to 3GHz

        Rf extends from the top of the very-high audio range (circa
        50-kHz) to several thousand GHz. (which will probably be the
        clock speed of Intel CPUs in few years).  Thousand+ GHz. rf
        is called millimeter waves  -- and is now the subject of
        much research and is extremely important in advanced
        radio astronomy.

TL>(course any part of the  spectrum could be called RF.)

        Oddly enough as it turns out, only the rf portions of
        the spectrum are called rf.

        The rest are called things like "audio frequencies", "infra-red",
        "visible light", "ultra-violet", "gamma-rays", "x-rays", etc.

        Once you start doing some reading you'll find terms like these
        cropping up all the time.


TL>A Tesla coil's tank circuit I presume
TL>would produce frequencies and harmonics covering a wide range of the
TL>spectrum.

        In the case of  =disruptive discharge=  coils, amen brother,
        amen.   Vacuum tube coils can be much better controlled.

        The stray frequencies occur at even multiples of the
        fundamental and are important out to at least the tenth
        harmonic.

TL>Also, I am not quite clear on how the RF destroys the neon.

        That is because you are not quite clear on how a transformer
        is designed (or works?).

        Suffice to say, the higher the intended operating frequency
        of a transformer the less iron is used.  Likewise, the thinner
        the laminations.  At a sufficiently high frequency any kind
        of lamination is too thick and powdered iron is used.  Above
        that even powdered iron is too heavy and molecular iron must
        be  used -- in the form of ferrites (for instance).   Beyond
        that point no iron whatsoever can be used -- only air
        itself as a core -- like -- oh, gee -- uh -- like in a
        Tesla coil!!??

        Neon transformers are loaded with iron.   When rf enters a
        neon transformer the poor, dumb transformer tries to
        transform it (because the transformer is not quite clear
        on the fact that it's rf).  This results in massive losses.
        The losses show up as heat.   The neon transformer is not
        designed to dissipate much heat.  Poof!

        There is also dielectric (heating) losses in the insulating
        pitch.  Poof!

        Due to resonance-rise the rf voltages are quite apt to be
        2, 3, or even 4 or 5 times the voltage of the neon trans-
        former secondary.  Neon transformers are not designed with
        much excess insulation.  Poof!


TL>Is it because it is high frequency, or high voltage, or both?

        Yep!  (I do believe it's what I just said)


                                             Quite clear (Hey!) on
                                             physics -- in Detroit, USA

                                             Robert Michaels