RE: Re: tank circuit of VTTC

[davidt-at-pond-dot-net (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hello,

Comments below,

--- Original Message ---
"Tesla list" <tesla-at-pupman-dot-com> Wrote on 
Tue, 22 Aug 2000 11:41:40 -0600
 ------------------ 
Original poster: "Herwig Roscher" <herwig.roscher-at-gmx.de> 

>>>>snip<<<<

> - Planned plate voltage?
10 kVdc. If this caused problems I could use 6 kV as well.
Some tube data for use as grid pulsed oscillator: peak dc plate

voltage 15 kV, peak cathode current 12 A, average plate 
dissipation 1000 W
 
> - Planned tank circuit C and L?
2.2 nF parallel 130 µH. L/C ratio is rather high as tetrodes
like 
higher load impedances than triodes.
 
> - Planned duty cycle (are you planning to drive from half-wave,
> full-wave, or filtered DC)?
Pure dc (filtered by one or some 15 µF/10 kVdc cap) as I'm 
planning on trying audio modulation. I've acquired a 3 phase
HV 
tranny from a mobile russian radar that will provide more power

than I'll ever need (weight 51 kg).

> - How many strings of caps will be connected in parallel?
1 string of 20 WIMA FKP1 2000 Vdc, 47 nF caps with dv/dt = 5000

V/µs

............... 

I would seriously think about using two stings of caps, with
some 40+ Amps, a single string will heat up on you pretty quick.
I have used a single string of the Panasonics at 5500  V, 1.7
pF 112 uH tank, filtered DC with two 833C's, and it does get
warm. (ceramic caps get down right hot, causing the C to drift,
wrecking havoc on tunning..., BTW)

Your #10 awg primary will be a bit overkill, but probibly worth
it. 

What are your specs for the secondary?

Good luck,

David Trimmell
www.ChaoticUniverse-dot-com

..................
> Assuming you're running in class C operation the peak-peak
RF 
voltage on your tank cap can be 2X the applied plate voltage,
and 
the peak circulating tank circuit current can be as much as 
Vplate*Sqrt(C/L).  
- So, 40 kVdc and 235 A (I peak) for the cap should be ok? And

AWG 8 is an overkill and AWG 10 is sufficient?
 
>Unlike a disruptive coil, a VTTC typically has a much higher
duty 
cycle... as much as 100% in the case of a system driven off a

filtered DC supply. The combination of high RF RMS currents and

high duty cycle make your application a potential capacitor killer,

especially as you begin to increase plate voltage.
- I've stated this already burning some ceramic rf caps.
  
> Flimsy leaded caps need not apply for this job... :^)
- Usually I'm wiring my MMCs with thick leads, but the internal

wiring of the caps....????

Regards 

Herwig