Corona and insulation Q

Buy some NOS corotrons! They show up on ebay.

--

John Larkin         Highland Technology, Inc

jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro   acquisition and simulation

And what after that one burns out?

Also, small world Bob :)

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

Eventually the stock approaches zero and the quality approaches zero as well. This design is to FIX them.

Yup! Have been selling buggy whips for 12 years now; this is another version..

50? 500? 5KV?

How long will the old color TV sets be around? The CRTs and other bits will die eventually.

25 KV from 500v sub-modules is ... computes furiously ... 50 modules!

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

For a moment, I suspected that I had experienced a time warp and found myself 30 years in the past. However, checking my PC's real time clock, all seems normal. Whew...

Try Super Corona Dope (MG Chem 4226):

I use the stuff to repair arcing Geiger counter and first generation night vision converter Hi-V power supplies. At 4KV/mil or 160MV/m (160 million Volts/meter), it doesn't take much to isolate 25kV.

There are also other alternatives with lesser dielectric strengths:

However, there's a catch. The "super" stuff should be heated in an oven to cure properly. Although claimed to be flexible, it does shrink slightly when cured, which can open air gaps, that fill with water, and eventually arc over. Although with lesser dielectric strength, the red stuff (4228) seems to be the best compromise.

I would be tempted to suggest common paraffin, which is good for about

40 MV/m (40 million volts per meter). The catch is that if it gets hot, it will melt or catch fire.

Incidentally, the liquid Corona Dope stuff is mildly conductive when wet. I was in a hurry and ran a test before the stuff had cured, and ended up with a nasty shock and some fried electronics.

Remember... you have only one life to give to your profession.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

HV, ground proximity, and unsealed nodes do not mix very well.

Way up on a high wire perch, several feet from the nearest attractor, yes.

In proximity to ground though. NOT. Needs to be fully potted at every node if it is above 1000V, circuit cards should also be potted.

Too many chances for coronal breech events and creepage causing carbon trails to form, and then ZZZZZAPP!

I have seen corona punch hair thin holes through 20kV HV wire insulation with only 12kV of pressure exertion. It was two wires, in fact, and only 6kV on each.

EL caps far sooner. Old TVs have little value.

I have "old" CRT style computer displays. Actually, only one, and it was the last of the line, top quality. A Viewsonic pro model with the fastest clock rate the industry made. 185kHz. I also have one of the biggest flat face CRT style TVs that got made. It is a Toshiba and the front face looks like it might be close to a half inch thick. Those are in mint condition and will still work. It wasn't very long after I bought those when I started getting flat screen LCD displays, and HDTV form factors ushered in.

computes furiously? Any math involving half of something (0.5) is easy. You know... 0.5, 5, 50, 500, etc. And you make remarks about my math, which you know nothing about.

What a stupid way to express insulation strength.

Per mil is the standard the wire makers use.

If you must use meters, then come up with something more tangible to the circumstance like "per tenth or hundredth of a millimeter".

That way, some on can picture the thickness of their wire insulation and easily figure what it can withold.same for beads of potting like RTV, etc.

Their only drawback is that one needs a vacuum to properly pot something against HV incursion. An air bubble means those numbers no longer work.

With HV, you usually only get to make one mistake.

You are lucky you survived yours.

As a child, I made the mistake of touching my jacob's ladder... Once.

I too, am lucky I am still here.

nt

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Be careful, very, very careful.

I know you know this, but....

From memory, curvature of a 1 inch ball diameter will hold off 20kV in air. translation no sharp edges.

In high voltage just think EVERYTHING conducts, just at different currents. Which translated means. if you don't put insulation in properly, you have more layers than you expect with voltage separations you also didn't expect: GND - air - insulation - air - HV

With small but finite current flow you can get some great fields across that air bubble and because it is too small to hold the resulting voltage impressed upon it, you get ARCing. Arcing, even invisible arcing, can lead to deterioration and catastrophic failures.

So you need to make certain there are no voltage gradients that exceed any of the materials' characteristics ANYWHERE

Back to your requirement, kapton is great dielectric strength but you have to extend it waaaaay out so the surface conductivity doesn't bit you. Mental model I use is to assume that EACH material is a resistor with coating of metal on each surface. Now consider what that looks like in your field. Well, not so much coating of metal as much higher conductive surface that likes to distribute charge evenly - like metal.

Get a Bell Jar, pot the structure while evacuating the air - it will probably look like foam of boiling water, but when sets up, you will have the insulation strengths you need. All can be done at low temp to not destroy what you're building. Should be good up to 45kV

Nobody else is.

You never do any math, so naturally we know nothing about it.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

What a bizarre thing to say from someone who recently claimed to be a scientist.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

The various data sheets and tables come in two flavors. MegaVolts/meter Volts/mil I tossed a coin and used metric. I like to use metric for engineering and US/imperial at the supermarket. Conversions are easy enough:

I thought about doing that, and decided that SI units were good enough. Dividing by 1,000 to get 40KV/mm is easy enough.

Maybe. Dry air is still 3MV/meter (3KV/mm) which is probably tolerable given a sufficient air gap between conductors. What's not tolerable is humid or wet air, which may as well be a short circuit. Some of the HV potting compounds contain solvents that are hygroscopic (absorbs water) that must be baked out. Of course, vacuum is best, especially for potted assemblies, but oven baking seems to work well enough for thin coatings.

I was saved by the invention of the transistor. In the 1960's, when I was working with tube type mobile radios, we used to kill or seriously injure about one technician per year in Smog Angeles thanks to the high voltages involved. I almost met an early demise when probing around the final amplifier cage holding a grounded microphone in one hand, and a neon lamp in the other, looking for RF leaks. Instead, I found the plate cap. That last thing I remember before the lights went out was the bright purple flash from the NE-2. Lesson learned. Next time I had the newly hired interns probing around with a neon lamp.

Ditto. I thought it was fun to watch paper burn and float upwards with the spark. That worked great until I tried it with a partially charred piece of paper. I didn't get the full power of the neon sign transformer, but it was enough to get my attention.

It's ok to believe in luck. The problems occur when you rely on it.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

So the dielectric strength of an epitaxial deposition is given in Megavolts per meter? I don't think so.

That's what we have redundancy for. (usually) And try to keep single point of failure situations to a minimum.

I do not need a double, but often wish I had one (a clone of myself) for an alternate purpose. Personal slavery! (gives 'personal' a whole new meaning). Then, I could get almost twice the work done!

Why not a direct multiple? Because even my direct clone could not possibly be as smart as I am and would not resolve and decide things quite as well. So the timeline suffers. :-)

Just remember, if it comes at us as fast as that baseball, we won't even know if the Mayans were right or not.

It's been done. Didn't work out well.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

Epitaxial deposition? Word salad.

In SI units, the basic electric field unit is volts/meter. MV/m is perfectly reasonable.

Wire makers are not scientists, and neither are you.

--

John Larkin                  Highland Technology Inc
www.highlandtechnology.com   jlarkin at highlandtechnology dot com   

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME  analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators