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Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
I acquired a cute little high-voltage shunt regulator tube at the swap meet last month. It's a Corotron GV5A-2500, made by Victoreen in Cleveland, Ohio. Rated for about 1.0 mA continuous and 1.8 mA pulse current. Searching for a datasheet also turned up reports that these are no longer manufactured, but old stock is in demand to sustain oil-well logging instruments, etc. (A challenge for solid-state substitutes is the need to operate at temperatures above 180 degrees C. )
I know these tubes conduct at a well-defined voltage because of corona discharge, unlike the glow discharge in lower voltage regulators. But want to learn: Do they have a negative resistance region? A striking voltage higher than the sustaining voltage?
I could find out soon enough in the lab. The project concept, contrived to use this component, is a simple circuit to quickly and repeatably charge a 52 uF pulse capacitor to 2500 V. The average charging current will be many times greater than the Corotron rating, if unregulated HV supply is adjusted to about 2800 volts with series resistance of about 300 K ohms. No need for a voltage meter if full charge is directly indicated by glow from the Corotron. If that's too dim (or physically shrouded) to see without darkening the room, we can put an indicator LED in series with the tube. Trust me to protect them against voltage reversal at pulse discharge time. But if the regulator tube needs extra voltage to strike, it could form a relaxation oscillator or sustain a damaging current pulse from big capacitor.
[edit] Just found this paper that predates commercial Corotrons: High Voltage Stabilization by means of the Corona Discharge between Coaxial Cylinders. Ain't the Internet great! The paper addresses min & max capacitance values for stability, but only for an operating region (relative source voltage and resistance) rather different from mine. Above a threshold current their (laboratory) devices could go into a negative-resistance glow discharge mode. Hope someone else here has some experience and/or suggestions! Rich
Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
The corona discharge voltage stabilizer is no more than a special case of the neon gas voltage regulator tube, and was occasionally used in the Thermionic Age to supply stable supplies in the region of a few hundred volts and some hundreds of microamperes. A typical device consists of two concentric metal tubes, separated by about 1mm.
It has similar negative hysteresis characteristics to other gas discharge devices, but at a very much lower current rating, and so can be made into a simple relaxation oscillator with C and R.
If you Google "gas discharge hysteresis" you'll find dozens of papers dealing with this phenomenon, and you'll see how you've confounded 'negative resistance' with 'negative hysteresis'.
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Do "corona" voltage regulator tubes have negative resistance?
Trust me to protect them against voltage reversal at pulse discharge time.
