Re: Ignatrons for sale

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Hi Jonathon,

As my wife always tells me, "If you don't know what it is, you probably 
don't need it..."   :^)

Seriously, an ignitron is a special purpose three terminal vacuum tube - 
basically a triggerable mercury vapor rectifier on steroids. The cathode is 
actually a pool of mercury sitting in the bottom of the tube (the tube must 
be oriented vertically). The anode is usually made of graphite (for high 
power rectifiers or medium power pulsed duty switching) or molybdenum (high 
energy pulsed power and low duty cycle switching). The third terminal, 
called the igniter, is barely immersed in the mercury pool. The ignitor is 
pulsed with respect to the cathode, usually via a capacitor discharge 
circuit, creating a small arc discharge between the igniter and the 
cathode. This puff of mercury vapor from the small arc then "fires" the 
ignitron into conduction in a BIG arc between the cathode pool and the anode.

Ignitrons are similar to Silicon Controlled Rectifiers (thyristors) and 
thyratrons - once triggered, they continue to conduct until either the 
current is reduced to zero or the cathode/anode voltage is reversed, 
reverse biasing and turning off the device. Ignitrons are designed to 
handle higher voltages and higher currents than most large single SCR's. 
Large ignitrons have been built to handle peak currents of hundreds of 
thousands of amperes at up to 20 kV.

However, ignitrons are slow. Some pulse-rated ignitrons are constructed 
with molybdenum anodes in order to safely withstand higher current pulses 
as well as short bursts of reverse conduction (as in an underdamped ringing 
LC circuit). Ignitrons can sometimes be found in high power magnet drivers, 
electromagnetic metal forming equipment, high power magnetizers, and 
industrial pulsed welding equipment. Even large ignitrons are gradually 
being replaced by thyristors. The recovery time of ignitrons is too long to 
make them of much use as spark gap replacements in a disruptive Tesla Coil. 
But pulse-rated ones would work fine in coin and can crushers.  :^)

Best regards,

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
"Electromagically" (TM) Shrunken Coins!
http://www.teslamania-dot-com

Tesla list wrote:
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" 
><Kidd6488-at-aol-dot-com>
>Hello everyone,
>        Can I ask, what is an ignatron?
>---------------------------------------
>Jonathon Reinhart
>hot-streamer-dot-com/jonathon
>In a message dated 11/14/02 10:06:01 AM Eastern Standard Time, 
>tesla-at-pupman-dot-com writes:
>
>>Chip
>>I have two ignatrons made by General Electric. One is a model #GL-7171.
>>It's a normal sized tube. The other is a monster model #GL-37207A.
>>Please pass on the info.
>>Thanks
>>Joe
>
>
>---------------------------------------
>Jonathon Reinhart
>hot-streamer-dot-com/jonathon