I Need Some Help With Grounding.

[Tyler Dami]

Hi All,

I really need help with the grounding situation. So...

I have a stainless steel chamber.
I have a 12kv NST, with no GFI. It has a grounding ouput.The outputs have microwave rectifiers (2) to convert the output to DC
I have a variable power supply.
I have a 2 stage 25 micron vacuum pump, grounded.

I'm really confused with it all. I know I have to ground the chamber, but too a normal wall outlet?
Is that safe?

The pics below show the pump and power supply.

Thanks soo much!!
edit: or not. The pics are too big. It says:
Luminous Tube Transf
Pir 120v 60Hz 360va
Sec 12,000V 30Ma
Sec Midpoint Grounded.
Again it will be used with two rectifiers.

-Tyler Dami

[Tyler Dami]

Ok, so update.

I will be grounding the High Voltage Power Supply & the Fusor chamber to a single wire, that goes to a 4 foot grounding rod. The Vacuum pump & Variac will be connected to a surge protector then a GFI outlet.

Will this work?

-Tyler Dami

[AllenWallace]

I'd also connect the chamber wall to the pump frame. This creates a ground loop, but this is not a problem because you are not using sensitive electronics and you are not carrying any current in your grounds.

I'm not sure why you feel the need for a grounding rod, except that if you add a capacitor you will have a LC circuit which will ring at RF frequencies. In this case, a good ground will reduce RFI.

I'd settle for all devices grounded to the AC center plug. Others may have a different idea.

[Richard Hull]

Ground lug grounding on the AC line cord is just fine. Ideally, a star grounding system is best, but not demanded. A star ground is best placed in the geometric middle of a project. I prefer my fusion chamber as it is large, metal, and has lots of bolts from which to further distribute the grounding. The line cord ground connects to the shell and on the same elongated bolt, I run a ground to the pump and power supply.

This is good practice but doesn't need to be obeyed unless a lot of lower level measurement instruments are in use or tremendous, rapidly switched currents are running about. It is also important if you are doing a lot of computer based data logging or have sensitive computer based controls within the system.

For the rank beginner, grounding is not such an issue beyond assuring that any metal shelled fusor is at a solid ground potential.

Driving a ground rod is just icing on a cake and not necessary at all here.

Richard Hull

[Tyler Dami]

Ok Awesome,

So just ground to a standard 3 Prong Plug. I'll use a surge protector just to be safe.

So right now I have the fusor shell grounded to
1. My main ground line.
2. My pump frame.
And everything is grounded to the same cord. (w/ surge protector)

Sound ok?

Just to clarify, the fusor ground doesn't actually carry any current. It just needs to have ground potential?

Thanks for the responses

Tyler Dami

[Carl Willis]

Tyler,

Just to clarify, the home electrical system ground should not be part of any intentional current path. The home electrical system ground that is being discussed is for safety, to hold equipment at ground potential so it doesn't ever "float" and become a shock or electrical fire hazard.

In standard fusor configurations, there is a current path between the NST metal case (tied to the secondary center tap) and the fusor chamber--current is flowing from the chamber to the grid, through the rectifiers, through the NST secondary, and back to the chamber to complete the circuit. So you should have a wire connecting transformer case and fusor chamber directly, in addition to whatever safety grounding you implement with the home electrical system.

For what it's worth, your images aren't available. This is probably due to an incompatible format or too large size. Stick with jpg, gif, or bmp < 1 MB.

-Carl

[Tyler Dami]

Ok Here is a pic of my setup based on the help you guys have given me.
Thank you all so much.

-Tyler Dami

[Tyler Christensen]

That is appropriate grounding, so long as the ground wire is also earthed to your house ground or some other dedicated ground (although no reason the house ground wouldn't be fine for this setup)

[Tyler Dami]

Awesomesause

Expect first light pics withen the next week.

Thanks.

Tyler Dami

[Richard Hull]

Again, the star point, ( fusor shell), should be the location of all electrical grounds as well as the fusor's shell power supply return line, as Carl notes. You have it drawn correctly.

Many use a separate, professionally manufactured supply. Some supplies have positive and negative fully insulated and floating. In this case the positive high voltage would have to go to the fusor shell and the negative lead would be hot and go to the inner grid.

Many supplies, most actually, avoid having to insulate and have one side grounded to the power supply's metal case. In this instance, the supply must be a negative "hot" supply or have internal provisions for diode reversal.

All this is not meant to confuse, but to let you know that should you move on to a formal supply, you would have to be aware of its configuration.

Making your own supply, as in the case of you demo fusor, you control the system from the base level.

Richard Hull

[benbartlett]

You only need one bridge rectifier, not two. Do you mean diodes?

Also, any three-prong ground should be fine, although a dedicated earth ground is preferable. However, at least check the continuity between line and ground before hooking it up and expecting it to be grounded, as many home outlets (especially older ones, like mine) often have broken or faulty grounding connections. Better safe than sorry.

Ben

[Tyler Dami]

Hi,
I just used two microwave diodes. Its a NST so I followed the schematic on the high voltage FAQ's.
The diodes are pointing towards the power supply - this is correct, right? Then the wires converge to one and go to the center grid. The outer shell is then grounded to the power supply grounding nut. All of this is using high voltage cables.

See the diagram.

Thanks,
Tyler Dami

[Richard Hull]

This is correct. You only need two diodes for full-wave rectification. You will get one half the nameplate voltage times 1.414 as the peak voltage out of your arrangment under no load conditions.

example

15kv neon xfrmer......

7.5 X1.414 = 10,600 volts approx This peak will be reached 120 times each second under no load.

Once you strike a plasma, you will never be able to reach this voltage, depending on the current drawn based on the magnetically shunted design of the transformer.

Richard Hull

[Tyler Dami]

Ok.

Should the grounding post on the NST be connected to my outlet too?

[benbartlett]

If what you are saying is that all grounded points on your fusor go to one common point (this is called "star" or "radial" grounding), and that point is what you mentioned as the "NST grounding post", then yes, you can ground the center point to as many grounds as you want.

However, when you say "NST grounding post", do you mean the case ground or the center tap? I attached a schematic of how most 2-diode demo fusors are wired.

Ben

EDIT: Color code:

Black: Diodes and fusor shell
Blue: Negatively charged items
Purple: AC items (also AC going to ground)