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RE: [TCML] Capacitor Questions



Hi Bob,

With #1, the beefy stud terminations sound promising, but the glass case is a little scary. With #2, the wide tolerance suggests that it is a ceramic dielectric.  The losses are likely to be high, but also, the temperature coefficient is likely to cause the cap's value to change significantly as the unit operates and detune your coil.  Warm it up slightly and see if the measured value changes.  If it does, I'd keep looking :-(

Regards, Gary Lau
MA, USA

> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of Bob Deuel
> Sent: Tuesday, May 26, 2009 10:49 PM
> To: tesla@xxxxxxxxxx
> Subject: [TCML] Capacitor Questions
> 
> Hello:
> 
> I have questions regarding a couple capacitors that I have:
> 
> 1) The first capacitor is a Sprague type 45P5 "Vitamin Q" rated at 0.012 mfd. @
> 25,000 VDC. It physically measures approximately 2.5-inches in diameter and 6.5
> inches long with end caps threaded for 1/4-20 thread. It is an oil filled capacitor that
> has a glass cylinder with metal end caps. I understand that some capacitor
> dielectrics do not take kindly the rigors of Tesla Coil operation and overheat. I
> wondering if anyone has used a capacitor of this type? This one would use for a
> future coil if it is acceptable.
> 
> 2) I plan on building a table top coil using a 5kv @ 20 ma. NST soon. I keep looking
> at a capacitor that is on my bench that I believe was from an older IBM computer
> monitor. It is made by ERO and is 9000pF+80-20%/20KV. It actually measures
> 10,300 pF which is great. Physically, it is potted unit in a 1.5x1.75x2.75 plastic case
> with a insulated HV lead and a "ground" lead. Are capacitors like these acceptable
> for a small coil or should I forget it and go with a MMC?
> 
> I would appreciate your input on the feasibility of these two capacitors.
> 
> Thanks,
> Bob Deuel, K2GLO

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