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Re: [TCML] Odd VTTC Streamer Behavior



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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