underwater arc

[lztwl]

An electrical engineering company designed an electrical component that would arc underwater many years ago. I would like to reproduce this. This is what I know;
This was not an arc welder.
The power source was a generator. 500 amps 100 volts, when not under load.
Power went through an isolation transformer for safety.
Also I believe inductor coils or chokes to protect the generator.
The plates the power traveled to were submerged underwater so the arc would not travel across the surface of the water.
The plates were 3/4" thick, 6" wide, and 36" long. This is the surface area exposed underwater.
The gap was 5/8" between the plates.
Resistors were used to start the process then they were bypassed.
I believe they also used a capacitor bank but I do not know what the rating was.
The arc seemed to pulse, when one was finished the next started, like a jacobs ladder.
I think the power was AC not DC

My question is, in building the system what components do I use to make this arc underwater. I am not an electrical engineer and would have a professional build it. I have tried 3 electrical engineering firms and all have failed. The first one I hired to do this years ago are not available any longer. If you can help please advise. Any help would be appreciated

 

[lztwl]

Just to add a little more. The engineering firm used not fancy electronics to fire the arc. Only the components I discribed. I may have missed something but no fancy electronics were used.

 

[MikeHalloran]

An arc welder uses the arc to melt metal, which subsequently solidifies in a different form, bonding pieces of metal together.
Call that the arc's mission.

What is the mission of your arc generator?
I.e., it's clearly possible to strike and sustain an arc underwater, but what then? What are you going to do with it?




Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

I would try spacing the plates a little closer together at the lower end. Put the plates vertical so that the arc can rise 36 inches. Convection may carry the arc upwards as it does in a Jacobs ladder. Use a welding generator if avail;able. It is used to that duty.
Is this salt water or fresh water?
Are you heating water? Don't need an arc for that. I have used truck leaf springs in a plastic barrel of salty water to load test generators when that was all that was available. Boiled a lot of water that way.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[lztwl]

Hello,

Salt was added to make the water more conductive and the plates are oriented vertical in the tank. The gap between the plates is so water can pass through them. I just stated a welder was not use so no one would suggest this as a possible optional power source. A welder will not work as we have tried it. We are not striking an arc. The arc must be able to jump the gap on its own. I was just thinking maybe the correctly sized capicitors would store enough energy to allow the spark to jump but did not know how to figure out the correct size. And you are correct the water will get very hot. This is expected and a desired effect. I think we also have the plates slightly closer at the bottom and the convection does help carry the arc a to the top.

Does anyone have an easy to follow formula for sizing capacitors? The ones I find seem way over calculated. I have 100 volts and 400 amps AC. I thought a formula should be easy but maybe I need more education on capacitors.

Thanks

 

[alehman]

Pure water has a very high dielectric strength - 70 kV/mm or so. That's why it's used in some electrical equipment. Not sure about salt water.

Alan
“The engineer's first problem in any design situation is to discover what the problem really is.” Unk.

 

[MikeHalloran]

Iztwl, you have provided a decent description of a device that we all know as a salt water resistor. All it does is convert electricity to heat. It does not normally produce an arc.

Can you possibly reveal what you are intending to do with it, once built?



Mike Halloran
Pembroke Pines, FL, USA

 

[waross]

This was not an arc welder.
The power source was a generator. 500 amps 100 volts, when not under load.
Power went through an isolation transformer for safety.

Why do you want an arc? To start an arc between those plates when there will be so much current flowing through the water will be difficult.
There is so much that you don't understand or remember that we are on the verge of wasting our time.
Your prejudice against welding machines seems strange.

Bill
--------------------
"Why not the best?"
Jimmy Carter