Thyratron switched coils
From: richard hull [SMTP:rhull-at-richmond.infi-dot-net]
Sent: Monday, April 20, 1998 6:47 PM
To: Tesla List
Subject: Re: Thyratron switched coils
>>According to p 201 of Sarjeant and Dollinger, the heating factor is
>>calculated from peak Vpeak x Ipeak x PRF
>>but devices can be run in excess of this. The book quotes a CX1159
>>being run at 30 times the value suggested by the heating factor.
>>Remeber that it is the average current that will likely destroy the
>>device. The rate of change of current in TC primaries will not damage
>>Richard Craven, Malvern, England
Richard is correct here. The average dissapation is the major factor in
using these babies. small coils might have about 100 amps in normal use for
a peak and let us say 10kv That is ~10E6 that allows over 1,000 PPS and
you are running well within the heating factor of a 5C22. With
non-continuous duty such as 3-4 minute runs, the full 300 amp plus peak
current could be called upon for `15,000 volts at 2,000 PPS and that would
be about a 9E9 and would be a "no sweat for this tube. That works out to a
maximum of 2000 4.5 megawatt pulses every second for a table top system!
A real no-no is holding the grid on as the tank current reverses. Oh, it'll
survive, but the fireworks show inside the tube is a scarey thing to see!
The tube life is, of course, shortened in this condition.
Glass H2 thyratrons run hot as hell! This is due to the "pot bellied stove"
sized cathodes running at a dull red heat in idle mode. If you haven't seen
the giant 1" diameter cylindrical cathodes up to temp or left skin on a
powered down tube then you haven't had the thrill of controlled high power
pulse operation that is silent.
Normal dissapation on Ceramic H2 thyratrons make the glass H2s look like
Amana deep freezes. I have an little tiny EG&G ceramic grounded grid H2
thyratron which is supposed to normally run at a case temperature of 765
degrees F!!! They warn against running the envelope much cooler than
this!!! The tube is only 2" tall and 2" in diameter and will handle 10,000
amp pulses at 18,000 volts. That is about 180 megawatts per pop! Typical
switch times are on the order of 7 nanoseonds.
Richard Hull, TCBOR