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Tesla coil in the rain

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LAN_403

teravolt

Fri Aug 13 2010, 03:22AM

Registered Member #195 Joined: Fri Feb 17 2006, 08:27PM
Location: Berkeley, ca.
Posts: 1111

the problem is that rain water conducts. maby under a large tent or better yet a building. I wonder what would happen if it was lit off in a fog

Mike

Fri Aug 13 2010, 05:36AM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

I have always been very interested in operating a tesla coil in rain, something like a fully enclosed plexiglass coil with only the toroid or breakout point exposed. I want to study the effects of rain drops to see if streamers do anything different, definitely on the to do list some day.

Martin King

Fri Aug 13 2010, 01:19PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Goodchild wrote ...

It's not just that, but water can be very conductive at high voltages if it got in the wrong place at the wrong time I can see it shorting things in the coil and/or the power supply.

Over all electricity and water don't mix.

You wouldn't get in a bath tub with a toaster would you? It's the same way I wouldn't get in the rain with a tesla coil.

Just my thoughts.

No I wouldn't get into the bathtub with a toaster as that would be stupid but I quite happily use an electric kettle, steam iron, have an electric immersion heater and so on. Electricity and water CAN mix if suitable precautions are taken which is the idea of this thread, to discuss what those precautions should be. Regards water getting into the electronics the original post mentioned that they would be made weatherproof but in more detail :-

Base - 12mm PVC and hardwood (with waterproof varnish), stainless hardware and all joins/cracks sealed with silicone or rubber gasket.
Join between removable secondary and base sealed with rubber gasket.
Cables from base to primary fed through nylon IP68 cable glands.
Rain shields over air intake/outlet.
PCB's and any internal vulnerable connections coated with conformal coating.
Mains connection via waterproof/weatherproof Buccaneer (or C form undecided as yet) connectors.
Fibre link to remote controls.
Isolation transformer.
Anything else that becomes apparent as construction continues.

Which I think pretty much covers weatherproofing. The issues with ground currents needs thought if indeed they are a serious problem? I guess a galvanised chicken-wire mesh secured to the ground with metal stakes at regular intervals and maybe bonded to a proper ground rod at each corner would probably be suitable. It's interesting that other people have though about this but seems no one's tried it yet so I guess the only way to find out is to get it finished and (carefully) try it

Martin.

radiotech

Fri Aug 13 2010, 03:14PM

Registered Member #2463 Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546

bonded to a proper ground rod at each corner

The grounded mesh may create more problems than it solves. In addition to bonding the rods to the chicken wire, the entire system has to be bonded to the grounded conductor of the power source for the system because the whole mesh could raise to 120 volts easily on circuit fed from a 15 amp breaker.

Ii you have 3-3 M rods over a 9 M^2 area A , B, C. you can measure R a-b, b,c, c-a. Then solve for R I doubt that in unsalted earth you would get less than 10 ohms.

Electrical codes use rods for lightning protection only. Lightning doesn't always seem to obey ohm's law.

Goodchild

Fri Aug 13 2010, 04:48PM

Registered Member #2292 Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795

radiotech wrote ...

Electrical codes use rods for lightning protection only. Lightning doesn't always seem to obey ohm's law.

Nor do tesla coils

Martin King

Fri Aug 13 2010, 06:41PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

radiotech wrote ...

the entire system has to be bonded to the grounded conductor of the power source for the system because the whole mesh could raise to 120 volts easily on circuit fed from a 15 amp breaker.

Shouldn't be a major problem, the vast majority of our shows are powered from an on site genset so we have complete control over grounding besides there has to be a certain aspect of if you're close enough to be able to touch the mesh when the coil is operating then you're too damn close anyway!

Martin.

Killa-X

Fri Aug 13 2010, 11:02PM

Registered Member #1643 Joined: Mon Aug 18 2008, 06:10PM
Location:
Posts: 1039

Would it be possible for streamers to actually be longer (with a nearby ground rod) during a fog? Since a fog is just small water drops that er close together, if it's a dense fog. Since water is more conductive than air id imaged, streamers could possibly pull longer and cause shock hazard...

If you do it all right, it could be done I'm sure. Like if you have a 4.5" secondary, put a 5" acrylic tube around it, all the way to the topload, to help prevent secondary arcs...And do the same for primary protection. This way, everything is covered up from moisture, except the topload :)

Phil T

Sat Aug 14 2010, 11:06AM

Registered Member #1974 Joined: Mon Feb 16 2009, 10:28AM
Location: United Kingdom
Posts: 9

It would be a good idea to see how your Public Liability insurers feel about it.

Phil

Martin King

Sat Aug 14 2010, 12:15PM

Registered Member #3040 Joined: Tue Jul 27 2010, 03:15PM
Location: South of London. UK
Posts: 237

Phil T wrote ...

It would be a good idea to see how your Public Liability insurers feel about it.

Phil

Of course but as we already chuck a load of fireworks into the air have several hundred litres of pressurized burning liquid and propane on site I suspect a Telsla coil with a proper risk assessment and testing isn't going to add to much to their worries.

Martin.

Reaching

Sat Aug 14 2010, 06:42PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

Just try it out. that would give you the only realistic answer. everything else are just presumptions.

i mean, for sure, the secondary coil must be coated in some waterproof material, otherwise the water can cause inner winding shorts etc.. the electronics must be waterproof too, but that would not be the major problem.

i think, when the coil produces an ground arc, the wet ground can cause the current to travel some distance, to a person nearby for example.. very dangerous in my opinion.

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