High Voltage Grounding

This forum is for specialized infomation important to the construction and safe operation of the high voltage electrical supplies and related circuitry needed for fusor operation.
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Liam David
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High Voltage Grounding

Post by Liam David »

I recently acquired a 15 kV 60 ma NST. When I hooked it up to my demo fusor, I got the exact same plasma I had at 3kV, just plasma around the grid wires and not in the center. Also, I've been running the fusor with the positive on the chamber wall and the NST case and the negative on the inner grid. I don't know how to properly ground the positive and the chamber like in all the diagrams I've seen. How should I ground the positive and the chamber? I don't want to drive a stake into the ground outside. Would this be the reason for not getting good plasma?
-Liam
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Richard Hull
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Re: High Voltage Grounding

Post by Richard Hull »

I have clear diagrams of a fusor power supply using a neon sign transformer in the FAQ of this forum.

viewtopic.php?f=29&t=4405

When we say ground we mean the electrical outlet ground (green wire). This is a driven rod ground on most homes. The diagram shows this as the ground symbol (inverted triangle of lines.) the outer grid or metal chamber wall on a fusor is connected to ground, always.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Liam David
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Re: High Voltage Grounding

Post by Liam David »

OK, I didn't have the chamber connected to the ground wire. I just had the positive going straight to the chamber and not to the ground. I'll see if I get better plasma after I rewire it. Thanks for the info!
-Liam
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Chris Bradley
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Re: High Voltage Grounding

Post by Chris Bradley »

Liam David wrote:I recently acquired a 15 kV 60 ma NST. When I hooked it up to my demo fusor, I got the exact same plasma I had at 3kV
What makes you suggest you are applying different voltages between the two setups? Have you measured the actual voltages?
Liam David wrote:I just had the positive going straight to the chamber and not to the ground.
What colour is the positive output on your NST?
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Liam David
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Re: High Voltage Grounding

Post by Liam David »

I'm using a different transformer. For first light I used 3kV and now I'm using a 15kV. What do you mean by "what color?"
-Liam
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Chris Bradley
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Re: High Voltage Grounding

Post by Chris Bradley »

Liam David wrote:I'm using a different transformer. For first light I used 3kV and now I'm using a 15kV.
What voltage are each putting out when under a plasma load?
Liam David wrote:What do you mean by "what color?"
Well, how do you know you are connecting to the positive of the NST?
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Liam David
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Re: High Voltage Grounding

Post by Liam David »

Don't have a voltage divider, so I don't know the voltage. I'm using 2 12kV diodes in series to rectify the transformer, so I'm getting a DC current.
-Liam
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Chris Bradley
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Re: High Voltage Grounding

Post by Chris Bradley »

OK. Excuse the method of the question, I just wanted to clarify how you were making a 'positive' connection without leading you.

As Richard says, read the FAQS. There should be no positive connection, only a grounded connection and a negative one.

Also in FAQS to read up: The output of transformers depends on the load. Just because they are different transformers means very little to the voltage they will achieve under a low impedance load. 'Plasma around the grid' sounds like a low pressure set-up to me, so you are probably only achieving 700V to 1000V in each case, and if so then of course there will be no difference.
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Richard Hull
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Re: High Voltage Grounding

Post by Richard Hull »

Also read the "Files forum" section on neon sign transformers. There is much to learn in many scientific disciplines. This is why making a fusor is a serious and taxing DIY and why its completion is a true win in more ways than one.

The positive lead of any supply is always connected to ground at the power supply. It is fine to run a ground wire from the power supply to the fusor chamber body or outer grid as well. This is, in effect your positive connection to the fusor.

I have create a new FAQ for this..........

viewtopic.php?f=29&t=9107&p=62105#p62105

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Liam David
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Re: High Voltage Grounding

Post by Liam David »

Thanks! The FAQ clears up some questions I had.
-Liam
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