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Making HV Plugs And Receptacles From Banana Plugs & Jacks

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jpsmith123

Fri Nov 11 2011, 08:51PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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Posts: 843

I just tried another program called "Elecnet", a finite element solver like Ansoft Maxwell, and that gives yet different numbers...I hate it when things disagree like this.

Anyway, what I need to do sometime within the next six weeks is to finish the multiplier and encapsulate it with the Qsil 12 silicone potting compound I got (it'll expire by the end of the year).

Thus I have to make a decision on how to get the 50 kv out of the thing in a robust, reliable and safe manner. Even though the various solvers disagree (with CST giving the highest numbers), the numbers are all below 30 kv/cm if I use a 0.6" diameter insulator with a 0.2" conductor. So I guess I'll use 0.2" OD banana jacks recessed in the body of the 0.6" diameter ABS plastic rods, and then I'll have to devise some corresponding plugs to mate with them.

(It would've been easier if I'd just made two different single-ended (grounded) multipliers, one for positive and one for negative output, using RG213 cable, like Glassman does; that way my measurement problems would go away too).

Here's what CST tells me:
(Balanced Load Case)

And with one side grounded:

And here's what "Elecnet" says for the balanced load case (same problem geometry and boundary conditions):

1321043573 1321 FT127930 Two Leads Elecnet

Edit:

Ok I just figured out how to refine the mesh in Elecnet, and now I get a result that's pretty close to what CST is telling me. I was going to attach the graph but apparently I can't do that by way of an "edit" to my post.

jpsmith123

Fri Nov 11 2011, 10:28PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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Posts: 843

Here's the plot from the Elecnet simulation with the refined mesh, followed by the plot from Ansoft Maxwell:

And here are the two from CST, first using a hex mesh, and second using the tetrahedral mesh. None of these 4 results look exactly the same. Note that the result from the CST tet mesh shows about a 15% greater field amplitude (just outside the insulation) than the three other results. I suppose this one must be inaccurate.

Patrick

Sat Nov 12 2011, 03:29AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

its scary when we engineers have to commit to a design, yet the dam models dont agree!

Carl Pugh

Sat Nov 12 2011, 05:20PM

Registered Member #1064 Joined: Tue Oct 16 2007, 05:04PM
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No one has said whether they are designing plugs for AC or DC or pulse.
DC is at least 5 times easier than AC. (This observation is from practical experience)

jpsmith123

Sun Nov 13 2011, 04:28PM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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Posts: 843

It's for the 50 kv DC output of a multiplier. What I wanted is a floating HV power supply, primarily to be used for charging capacitors. I wanted it isolated from ground so I would have the option to ground either side, for a positive or negative output.

@Patrick: If I get the chance later I'm going to compare the results of these various programs using a simple coaxial cable geometry where the field can be easily calculated. Just looking at it quickly, it seems that CST is giving me pretty good numbers, but the field plots seem more artifactual, e.g., the plot doesn't correlate very well with the actual geometry - unless you have a ridiculously fine mesh.

Carl Pugh

Mon Nov 14 2011, 02:57AM

Registered Member #1064 Joined: Tue Oct 16 2007, 05:04PM
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Posts: 42

With 50 kV DC corona is not usually a problem. When the voltage is increased, there is some arcing and then the arcing stops. The potential then distributes itself according to the resistances of the insulation.
We used a Sorensen power supply at up to 60 kV for years with the coax shield just folded over and there was never any problem with the coax. The insulation over the coax extended maybe 10 inches past where the shield was folded back.

Patrick

Mon Nov 14 2011, 04:10AM

Registered Member #2431 Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639

there is a type of plug for RC applications (not tamaiya or deans) it comes with a female hollow part and then a male sping part, both are perfectly cylindrical, it would be easy to place them in cables or on box faces and panels. Though there not meant for HV id rather use these instead of banannas.

i wish i could remember the name...letme check.

jpsmith123

Mon Nov 14 2011, 05:11AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
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Posts: 843

I'm wondering, what kind of coax cable did you use, RG8 or RG213? And can I ask, what kind of HV receptacle did the power supply have; was it similar to the one I linked to above?

Carl Pugh wrote ...

With 50 kV DC corona is not usually a problem. When the voltage is increased, there is some arcing and then the arcing stops. The potential then distributes itself according to the resistances of the insulation.
We used a Sorensen power supply at up to 60 kV for years with the coax shield just folded over and there was never any problem with the coax. The insulation over the coax extended maybe 10 inches past where the shield was folded back.

Carl Pugh

Mon Nov 14 2011, 04:40PM

Registered Member #1064 Joined: Tue Oct 16 2007, 05:04PM
Location:
Posts: 42

The power supply was oil filled. The tank was not sealed (the oil was exposed to the air).
The coax entered the tank from the top of the tank, the shield was folded back and grounded to the tank. The coax inner conductor and insulation continued through the air space and entered the oil and the inner conductor was terminated in a bananna plug. There was never any problem with corona inside the power supply.
The Sorensen power supply was 60 hertz and used a doubler circuit.
This was some time ago and unfortunately I don't remember the type of coax used.

jpsmith123

Sun Nov 20 2011, 02:06AM

Registered Member #1321 Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843

I found some HV banana cables available commercially, but unfortunately the highest voltage rating I've seen is 20 kv.

So it looks like I will have to make my own somehow. The design and construction of a recessed panel mount banana jack seems straightforward enough, but the mating cable assembly would be problematic. I'm stuck on how to securely attach a banana plug onto the end of some HV silicone wire.

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