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Re: Tentative TC design: first considerations



to: Marco

Remember to consider the surge impedance of the transformer.  Most (even
with a primary inductor) will draw considerably more peak current than the
nameplate rating for very short periods of time.  This could throw your
calculations off ---- these factors must be measured and compared to theory
to make it accurate.

Your DC circuit will work fine and is best for modeling.  Even better is to
use a 7703 ignitron (mercury thyratron) or equivalent to allow for precise
firing.  To provide accurate timing a 3 kV trigger pulse with a 2 MFD cap
is recommended for the type 7703.

Using DC the quenching now becomes a more important factor than with AC
which is relatively self-extinguishing in operation.  Also, you must have
some bleeder resistors on the caps so they don't retain a lethal charge.

DR.RESONANCE-at-next-wave-dot-net


----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Tentative TC design: first considerations
> Date: Monday, November 30, 1998 11:57 AM
> 
> Original Poster: "Marco Denicolai"<Marco.Denicolai-at-tellabs.fi> 
> 
> These are just the first steps before writing a formal specification of
my
> TCs to be built.
> 
> In my understanding the AC xfrms used to feed most of built TCs are just
an
> extra sort a complication for its modeling. My TC uses actually "pulsed
DC"
> from its tank supply: that is, the tank provides a voltage changing from
0
> to 9 kV, 50 times a second (just to be sure everybody gets it). Because
> everything works fine this proves that TCs can be fed by DC: the primary
> capacitor doesn't need to be charged with varying polarity cyclically.
> 
> Now, we can imagine a tank DC supply with a bridge rectifier and a huge
> flyweel capacitor (e.g. 10 uF) using e.g. a pig. The pig primary would be
> current limited according to the flyweel capacitor value. This DC supply
> would be connected to rest of the primary circuit (capacitor, spark gap,
> primary coil) as usually, but through a second current limiter, this time
> set to charge the primary capacitor in a time smaller then the time
between
> bangs of the rotary spark gap. This will also protect the flyweel
capacitor
> from discharging too much when the spark gap fires.
> 
> Having a variac on the pig primary would allow to directly set the tank
> output voltage and we would be sure that the primary capacitor is always
> able to get charged to that voltage before every bang.
> 
> This means that we'll know precisely at what voltage the primary cap is
> charged i.e. we'll know exactly how much POWER we'll pump into the
primary
> coil at each bang (forget about the losses for now).
> 
> We could than easily investigate the effect of bang repetition rate
without
> bothering about the AC tank voltage, the bang phasing, the tank supply
> impedance, etc.
> 
> What about that?
> 
> Another thing that I don't get is why TC power requirements are usually
> defined as tank supply voltage and its current limit value: wouldn't it
be
> more exact to speak about power (Joules) required by the primary winding
> (easy to calculate from primary cap value and its charging voltage) or
the
> energy required (multiply by the BPS) ?
> 
> Eventually the most important thing that matters (again, forget about
> losses) is how much energy is stored in the primary capacitor, not its
> charging voltage, to define how much energy we are pumping into the
primary
> coil, isn't it?
> 
>