Re: [TCML] Odd VTTC Streamer Behavior

[futuret@xxxxxxx]

Ed,

The 8kV was the AC rating for the mica cap. It's rated for 11 amps at 
300kHz.
The coil operated at around 120kHz or so.  I was getting probably
35" sparks at the time.  I knew the rating was marginal, and I was
not surprised it failed.  Usually I use two of these in series, but I 
didn't
have the right values so I used this single capacitor.  I just offered 
this
information to give Phillip(?) an idea of what type of voltage
relationships he might expect.  I wasn't presenting it
from a engineering or scientific perspective.

John


-----Original Message-----
From: Ed Phillips <evp@xxxxxxxxxxx>
To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
Sent: Tue, 21 Oct 2008 6:07 pm
Subject: Re: [TCML] Odd VTTC Streamer Behavior


 
futuret@xxxxxxx wrote: 
 
> When I tried using a an 8kV rated mica transmitting cap 
> with a 6kVAC power supply, the transmitting cap failed. 
> So that may give some idea of what voltage ratios can 
> be withstood in a VTTC. Of course each VTTC maybe 
> slightly different, etc. 
>  
> For the other original issue... the problems over 
> 105 to 120V: 
>  
> Another possibility is that your staccato board may be 
> being affected by the RF. That may be disrupting its 
> operation at the highest powers. Better grounding 
> or bypassing of the staccato power supply may help 
> if that's the problem. I=2
0had plenty of those problems 
> when I first was perfecting the staccato concept. 
>  
> John" 
 
  The 8 kV was probably a DC rating and you attempted to operate it way 
above ratings for the frequency you used. Transmit micas are normally 
rated for different currents at different frequencies; the product of 
the rated current at a particular frequency times the reactance of the 
capacitor at that frequency gives the maximum RF voltage, which is 
usually much less than the rated DC voltage. The reason for the current 
limit is heating due to the equivalent series resistance rather than 
voltage breakdown. Normally this information is on the name plate of 
the capacitor. 
 
  Other capacitors rated for RF service usually have similar ratings 
and these should be observed for maximum life. 
 
Ed 
 
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