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Tesla coil in the rain

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Martin King

Thu Aug 12 2010, 07:52PM

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

It's possible that the coil I'm currently building may end up being used in outdoor shows at some point in the future. Now assuming that all the electronics are thoroughly waterproofed (without compromising cooling) and only the Primary, secondary and top load are exposed to rain is there likely to be a any problems using it in drizzle/light or maybe even heavier rain ? I guess I'd need to drill some drainage holes in the flat part of the toroid (or change to a spherical top load), another possibility would be to put a plastic tube around both the coils so that only the top load is exposed to the elements.

Cheers,
Martin.

Goodchild

Thu Aug 12 2010, 08:03PM

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

I don't see running a Tesla coil in the rain to be very safe.

Martin King

Thu Aug 12 2010, 08:11PM

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

Goodchild wrote ...

I don't see running a Tesla coil in the rain to be very safe.

Why do you think it would be dangerous? Any remote controls would have to be completely isolated (fibre) and probably an isolation transformer on the mains but then for a show with a live audience then I would want everything to be isolated regardless of rain or not. I'm reasonably happy a coil could be operated safely in rain with the right precautions, it's more a case of would it actually work/produce sparks in the same manner as dry conditions, would rain affect the tuning of the coil adversely, that sort of thing.

Martin.

modularduck

Thu Aug 12 2010, 09:26PM

Registered Member #3094 Joined: Tue Aug 10 2010, 03:12AM
Location: portland, or
Posts: 30

I would think that standing water would be an issue and might cause errant voltage to travel long distances and endanger people even if they were quite a way from the coil its self. i.e. if you got a ground strike from the coil it could shock someone standing in a puddle some distance away. but perhaps i am wrong in this

Martin King

Thu Aug 12 2010, 09:39PM

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

modularduck wrote ...

I would think that standing water would be an issue and might cause errant voltage to travel long distances and endanger people even if they were quite a way from the coil its self. i.e. if you got a ground strike from the coil it could shock someone standing in a puddle some distance away. but perhaps i am wrong in this

Thanks that's the sort of thought through reply I'm interested in rather than a knee jerk "it's dangerous". My gut feeling is that once the spark hits ground that's pretty much it, electricity takes the easiest path to ground and that's not likely to be via a punter standing several tens of metres away. If it was an issue then I suspect a ring of copper pipe/wire around the coil at around it's maximum strike distance at ground level and attached to an earth spike (effectively another strike rail) would prevent any problems, otherwise the coil could be operated in a chicken wire Faraday cage but I'd rather avoid a cage.

Goodchild

Thu Aug 12 2010, 11:15PM

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

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.

Killa-X

Thu Aug 12 2010, 11:44PM

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

I always thought of this too, but would agree with Goodchild, yet I always wonder how a Tesla Coil would react in rain. Would the streamers just act normally, arcing random to air, and the rain does nothing because they arnt a 'shorter path to ground' so to speak, or would the streamers arc the raindrops?

Xplorer

Fri Aug 13 2010, 01:12AM

Registered Member #2416 Joined: Sun Oct 04 2009, 04:23AM
Location: Oceanside, CA
Posts: 91

If the secondary form gets wet it will likely conduct the HV streamers down to the primary circuit.

-Tony

Andyman

Fri Aug 13 2010, 01:20AM

Registered Member #1083 Joined: Mon Oct 29 2007, 06:16PM
Location: Upland, California
Posts: 256

^ That would be my main concern as well. Unless you covered the primary and secondary with some sort of highly hydrophobic material...

radiotech

Fri Aug 13 2010, 03:02AM

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

Step potential is the issue. If a high voltage line contacts earth live, and they do quite often in storms on unfused circuits that can dump tens of amps , the volts per meter on the surface can immobilize someone walking close by. This happens because the resistance of the earth, between to points approximating the distance beween two feet striding, will drop a high enough voltage, given the current flowing from the fault.
This cant happen in switchyards or substations or along the fence because under the surface
is network of bonded copper conductors and ground roda,(have built these)

A telephone magneto can send 10s of MILLIAMPS for miles through earth as return of a metalic side. But that is only because of the nature of earth resistance. This current can annoy earthworms up as fishermen know. if they look around the ground rods.

A streamer from a big Tesla coil might be able to output nasty, though not lethal current if the streamer and earth return impedance matched the output impedance of the coil and allowed the coil to stay resonant. As to 'step potential, not likely, for reasons stated above,

The multi-joule high voltage generators are a different story, if one of those discharged through earth in the rain, hard to explain stuff might happen, not lethal, but could cause injury if somone jumped or fell when they got zapped. (seen this)

Goodchild has some good points about what we do in the rain or water.

If you were running a TC in the rain and an incident happened, you would be hard preesed to explain you weren't responsible.

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