doorknob cap mfrs

From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
Sent:  Monday, June 01, 1998 7:50 PM
To:  tesla-at-pupman-dot-com
Subject:  doorknob cap mfrs

For those who are interested, if you are looking for doorknob cap
manufacturers, you might
try http://www.ceramite-dot-com, who oddly enough, make the "cera-mite" brand
caps formerly sold by Sprague.

Interestingly, their catalog gives dissipation factors for the various
doorknob caps. The familar DK series (I wonder how they came up with that
series designator?), the dissipation factor is a max of 1.2% at 1kHz.  The
faster KT series has 0.2% dissipation at 1kHz.

Their RF duty units have dissipation factors between 0.1% and 0.5%. They
are rated at a few amps of RF (for instance the 1000 pF, 5kV unit is rated
at 3.9 Amps, 0.2 kVA).

if you put the full 5 kV peak (= 3.5 kV RMS) and 3.9 Amps through the unit,
(about 14 kVA, the dissipation (at 0.5%) would be 700 Watts!!! 

Also, computing from their supplied equation: ESR = DF/ (2 pi F * C), a
1000 pF cap at 100 kHz has an ESR of about 80 ohms.