Re: VTTC capacitor

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "vladimiro mazzilli by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mazvla-at-iol.it>



Tesla list ha scritto:

> Original poster: "Steve White by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<slwhite-at-zeus.ia-dot-net>
>
> I do not understand your comment about pulse caps handling only DC. Even
> when used on a disruptive coil, every time the spark gap fires this closes
> the circuit on the primary tank circuit. The tank rings with a damped
> sinusoid (AC) each pulse. Thus, the pulse cap is subjected to AC. I happen
> to have a 0.0015 uf pulse cap rated at 15 KV. This should be a very good
> size for a tube coil. I am still seeking an answer to my question about
> frequency applicability of a pulse cap. I suspect that it it should not be a
> problem because most tube coils seem to operate at under 1 MHZ frequency.

I think it'is not a really  problem but I'think is better mica capacitors
or ceramic suited for
transmitting operations. Once I was working on a low power Royer converter
(Current fed resonant
push pull type)20Khz of resonant frequency, and I had very serious problems
with the capacitor of
primary resonance about the two collector or drain. Every type of
capacitors get very hot an
briefly destroy it .I take a look in tgdelta specifications and I found few
type of capacitors
(RIFA), that meet the high frequency data.With this, I solved my
problems.In my experience with
VTTC the film capacitors I speak of best type, get hot when tesla was
running, Mica or transmitting
type gave me the best response.

Cheers

Vladi


>
>
> Steve: Coiling in Iowa
>
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Monday, February 11, 2002 4:46 PM
> Subject: Re: VTTC capacitor
>
> > Original poster: "Area31 Research Facility by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <rwstephens-at-hurontario-dot-net>
> >
> > Steve,
> >
> > Tetrodes are poor choices for self excited RF power oscillators.  This
> tubes
> > triode counterpart, a 3-1000 would be an excellent tube.  All commercial
> > industrial RF induction heating systems that use tubes employ triodes for
> a
> > good reason.
> >
> > Pulse capacitors are usually designed for so many 'shots' or discharge
> cycles
> > with minimum percentage voltage reversal to none at all.  For this reason
> I
> > would have to recommend not using them in a CW RF tank circuit where 100%
> > reversal at the RF frequency is the norm.
> >
> > Relatively large values of tank cap are not normally used in VTTC circuits
> > because the oscillator tube plate represents a much higher source Z than a
> > spark gap switch.  The tank circuit must have an impedance at the Fo that
> > matches the plate impedance of the selected tube(s).  Tube circuits, even
> in
> > high powered coils in the tens of kilowatts often use cap values in the
> merely
> > 0.002-0.005 uF range.  More L is needed in the tank coil to compensate
> compared
> > to a disruptive TC with usually larger capacitance.  Mica transmitter
> > capacitors are ideal in this tube oscillator application.  'Cheese slicer'
> > mechanical variable capacitors with large plate spacings from commercial
> > transmitters and antenna tuners are also suitable as a tank cap.  They can
> even
> > be submerged in oil to increase their operating voltage and capacitance,
> or to
> > allow a lower voltage cap otherwise unsuitable, to handle the voltage.  I
> > suspect that the latest rage, the MMC using polypropylene/foil or
> deposited
> > foil would be fine as long as the relatively high tank circuit circulating
> > current ratings were respected in its design.
> >
> > The 4-1000 makes a very pretty display tube.  I have one in my display
> case.
> >
> > r stephens
> > >
> > > ----- Original Message -----
> > > From: <mailto:tesla-at-pupman-dot-com>Tesla list
> > > To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com
> > > Sent: Monday, February 11, 2002 08:59
> > > Subject: VTTC capacitor
> > >
> > > Original poster: "Steve White by way of Terry Fritz
> > > <<mailto:twftesla-at-qwest-dot-net>twftesla-at-qwest-dot-net>"
> > > <<mailto:slwhite-at-zeus.ia-dot-net>slwhite-at-zeus.ia-dot-net>
> > >
> > > Are pulse caps suitable for use with a VTTC? I am particularly
> interested in
> > > their high frequency suitability. Also, has anyone ever built a VTTC
> with a
> > > 4-1000A tube? Since this tube will handle over 1000 watts, it seems like
> a
> > > good
> > > candidate.
> > >
> > > Steve: Coiling in Iowa
> > >
> > >
> > >
> > >
> > >
> >
> >
> >