Re: [Fwd: Re: [Fwd: Re: [Fwd: Re: hyfrecator]]]

Tesla List wrote:
> >From gowin-at-epic-1.nwscc.sea06.navy.mil Thu Dec 12 14:35:45 1996
> Date: Thu, 12 Dec 1996 08:29:04 -0500
> From: Dan Gowin <gowin-at-epic-1.nwscc.sea06.navy.mil>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: [Fwd: Re: [Fwd: Re: [Fwd: Re: hyfrecator]]]
> All,
>     The following is from a private E-Mail message between
> Kristen Ukkonen, Brent Turner, and myself.
> The question is: Does a flyback transformer in a T.V. resonate
>                  at 15 KHZ, the horizontal scan frequency?
> Comments always welcome.
> D. Gowin


> >- Brent
> Surely, there can and will be resonant frequencies with the flyback
> transformer but IN IT'S NORMAL USE it's not run resonant!
> Heck, I'll have to actually measure the resonant frequency of several of
> the flybacks I have around here.. I'd bet that their resonant frequencies
> vary a great bit! Depending on core material, number of turns,
> size and shape of coil etc..
> Just think about it - assuming they are resonance driven would imply that
> ALL the flybacks would have to be carefully and accurately manufactured to
> be resonant at the spesific freq..  Possible, but I don't think so..
> Of course, I CAN be wrong but I strangely remember that some flybacks were
> resonant near 50kHz or 150kHz.. I'll have to MEASURE it to be certain
> though.. It's simple enough - if all the flybacks are resonant at
> the same freq. than you are correct..
> I'll mail you again after I measure some during weekend..
> Anyway, iI do KNOW that flyback xformers are not resonant driven in
> televisions.
> One more idea - if it were a resonator what would happen to it's res.freq.
> when you connected it to the picture tube - I'd guess the tube would act
> like a capasitor (toroids in TCs). One would need to assume that a
> specific flyback would need to be optimized with certain CRTs as
> well.
> Besides, I've seen a neat system running a flyback at 100Hz and getting
> 10cm (!!!) sparks out of the poor thing. Definitely not resonant, just
> lots of energy dumped to the core FAST.. The energy magnetically stored in
> the core is the source for the secondary voltage.. Like in induction coil,
> huh?
> Ideas and corrections welcome,
>   Kristian.

I will agree that the flyback isn't DRIVEN at it's resonant frequency.
However, from what I recall, the transformer secondary is designed
to resonate at either the 5th or 7th harmonic. Think about it - if
it isn't driven at resonance, than it's simply a high-voltage pulse
transformer, ala an induction coil. BUT, the goal of the transformer
is two-fold, 1) it provides the voltages necessary for the grids and
first anode in the picture tube, plus it generates the intense energy
pulse which causes the electron beam to 'zip' back to the left side
of the screen to prepare for the next horizontal line sweep. The other
purpose of the flyback is to generate the 12,000 - 30,000 volts for
the second anode in the picture tube. Now, if the high-voltage output
winding has good resonant characteristics, and we get our driving pulse
timing down, the resonant 'ringing' gives more AC peaks to be rectified,
and sent to the picture tube. Thus, efficiency is rather high.

- Brent