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Corona discharge

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LAN_403

Wastrel

Sun Feb 05 2017, 04:53PM

Registered Member #4095 Joined: Thu Sept 15 2011, 03:19PM
Location: England.
Posts: 122

Some ozone generators use the corona effect from a wire, but the real things use dielectric barrier discharge, which isn't the same as corona.

To demonstrate high voltages to high school children I think you'd be mad to use anything other than a Van de Graaf. It's the standard in school safe high voltage.

Hazmatt_(The Underdog)

Sun Feb 05 2017, 08:33PM

Registered Member #135 Joined: Sat Feb 11 2006, 12:06AM
Location: Anywhere is fine
Posts: 1735

I think Wastrel brings up a good point, as much as I dislike it because it's an example of "watered down" science these days.

Ultimately, you will need to talk with your safety officer and get your "system" approved, or you could easily loose your job.

I was trying to help my college science center get a Crooke's tube working again, the one with the Maltese cross, and those are pretty much banned these days for fear of X-ray generation.
Which is ludicrous, but that is the world we live in now, and that was almost a decade ago.

I cannot commit to anything because of work and people line-up to demand I do things for them (so I never get to my projects in time) but I may be able to machine a spinner for you. That's not a promise because I'm busy, and exhausted, but I can see what I can do.

You should also see what Fisher sci. has available, and do searches on old CENCO equipment, it's really good and has lasted 100 years. (I do like CENCO stuff, it's pretty neat)

Martin Slinning

Mon Feb 06 2017, 08:29AM

Registered Member #61375 Joined: Sat Dec 17 2016, 05:45PM
Location: Norway Aalesund
Posts: 13

Yes, safety is always focus nr1! We follow national guidlines with at least two safety barriers. I will point out that the students themself will not handle this equipment at any time. It will be demonstrated by me with safe distance to students. However i also agree with Hazmatt that we tend to move to "watered down" science to day. When kids need helmets just to go outside it has gone to far..

DekuTree64

Thu Feb 09 2017, 07:21AM

Registered Member #54596 Joined: Fri Mar 06 2015, 11:31AM
Location:
Posts: 19

Build a Bonetti electrostatic machine :) And perhaps a Wimshurst to get it started with, because the sectorless style is tough to get started if the humidity isn't low enough. But sectorless is a much better educational tool. With 15-20" diameter discs you can really feel the resistance on the crank, whereas a Wimshurst is so inefficient you can't feel anything beyond the friction of the mechanics. And the discs glow with corona where the positive charge is bleeding off into the air, bright enough to be visible to the whole class in a dark room. And you can make long sparks. And demonstrate how smooth surfaces can contain higher electrical pressure, with corona discharge being sort of like a leaky pipe :) And as long as you don't put any capacitors on it, it's safe to play with and stick your hands in it. The sparks sting a bit, but no harm done. Getting sprayed with corona and then shocking people with your static charge is also fun :)

Dr. Slack

Thu Feb 09 2017, 09:55AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

No need to use a Whimshurst to 'boot up' a Bonetti. A glass rod recently rubbed with a silk cloth, held close to one disk opposite a comb, is all that's needed to get it started.

Erlend^SE

Thu Feb 09 2017, 08:45PM

Registered Member #1565 Joined: Wed Jun 25 2008, 09:08PM
Location: Norway
Posts: 159

Use a flyback driver and TV transformer, also take the output via >10 (suggested 100) MOhm HV resistor.

ZVS does current well, you want voltage (thus flyback driver, 555+FET would be the crude form)

That way, it should be hard to get a dangerous output current.

Martin Slinning

Wed Mar 08 2017, 07:49PM

Registered Member #61375 Joined: Sat Dec 17 2016, 05:45PM
Location: Norway Aalesund
Posts: 13

Hi again. Thanks for all replies.

My goal is to make corona discharge between two (or three ) small lines of wire to demonstrate corona discharge in a powerdistibution net line in the most safe way for the students.(Zvs + TV transformer?) I was maybe a bit unspesific in my first post. Sorry for that.

Any suggestions?

Martin

Martin Slinning

Wed Mar 08 2017, 08:15PM

Registered Member #61375 Joined: Sat Dec 17 2016, 05:45PM
Location: Norway Aalesund
Posts: 13

I was of course interested in all cind of corona demonstrations, but for these studendts, the high voltage powerline distribution corona discharge are the most interesting to be awere of.

DerAlbi

Wed Mar 08 2017, 10:26PM

Registered Member #2906 Joined: Sun Jun 06 2010, 02:20AM
Location: Dresden, Germany
Posts: 727

So from university teacher to university teacher

Use a dark room. Use very thin wire, (the thinner, the earlier it glows)
You can easily explain that to the students and even reference that to every day technology.. like HV-Lines made out of 4 thiner strands.. not to carry more current, but to increase the effective wire diameter without sparing that much material so the electric field is not peaking so high.
Then you can explain why different voltage lines will have different geometry, like the common 2 strands, 4 parallel wires, or even 8 on really high voltage lines.
You can even demonstrate the same voltage on different wire diameters and show that they start to glow on different voltage levels in that manner. Then you can make small notches in one thicker wire and show that those imperfect areas break down easier. Then make references to rain drops or dirt on insulators and stuff.
I think for the practical understanding of the phenomenon and with respect to power transmission, this would be the most relevant stuff.
For this i would suggest even DC voltage or a flyback.
I think this is a visible thing. Touch or interaction is not important.
Turn on, show, turn of, change wire, turn on... and so on. Safety is only a concern for you, students should not be able to interact with the stuff.

If you cant make sure of safety, then use high frequency like 1MHz++. This will glow somewhat like DC but when you touch it you dont get electrocuted, it will just leave a burn mark that will heal. Its safe due to skin effect.

Newton Brawn

Thu Mar 09 2017, 02:34AM

Registered Member #3343 Joined: Thu Oct 21 2010, 04:06PM
Location: Toronto
Posts: 311

LOOK here

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