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Plastic Polystyrene Plate High Voltage Capacitors

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Adam Munich

Wed Sept 15 2010, 02:00AM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

Yeah like I have access to a CO2 laser. I do have access to a CNC, but I fear the aluminum would just rip and get tangled around the spindle. That wouldn't be too good.

HM_Murdock

Wed Sept 15 2010, 02:01AM

Registered Member #3075 Joined: Fri Aug 06 2010, 02:44PM
Location: Athens, GA
Posts: 148

Pressure is key...it adds capacitance (as in, from 3nF to 15nF just by adding pressure from the clamp)...

these particular 6" plates are not suitable I don't think...

May try some regular sized plates tomorrow (these were the only 6" ones I could find locally so far), as the choices are more varied and they will be thicker by nature. I was hoping to stay with the smaller plates for convenience of size, but I am tired of blowing the things through...

I was also really hoping to pull this off without oil (too much of a potential for a mess), but it may not be possible

EDIT - lol with Grenadier...I hear ya man, I don't have one of those laying around at my disposal either...

I also believe the whole point of this thing to is to find a cheap, DIY cap that's quick and easy and can be constructed from every day materials.

Russell Haley

Sun Sept 19 2010, 04:10PM

Registered Member #2478 Joined: Mon Nov 23 2009, 03:24AM
Location: Texas A&M University
Posts: 47

What about using foam plates instead of plastic ones? That would make the capacitance variable over a larger dynamic range, and:

U. S. Patent 5541366

Examples of such materials include foamed polystyrene, such as Styrofoam.RTM.. Typical electrical properties of Styrofoam.RTM. 103.7, measured at 3 GHz are a dielectric constant of 1.03 and a dissipation factor of 10^(-4)

If that number is accurate, a foam plate stacked capacitor could be suitable for continuous operation with large RF currents, provided you could get the small amount of heat away fast enough. Heavy duty foil and oil channels punched out of the foam, perhaps?

Mike

Tue Sept 21 2010, 05:21PM

Registered Member #58 Joined: Thu Feb 09 2006, 05:40AM
Location: Tri-Cities, Washington, US
Posts: 317

seems to me those would be pretty large considering how thick and how much air is in the foam. but give it a try and let us know.

Russell Haley

Sun Sept 26 2010, 10:05PM

Registered Member #2478 Joined: Mon Nov 23 2009, 03:24AM
Location: Texas A&M University
Posts: 47

I built one using 10 inch foam plates. With 10 plates (that is, 10 with voltage across them) I measured (1 kHz) 1.071 nF with no clamping force, 1.43 nF with a substantial fraction of my body weight, and 1.300 nF with a stack of books. The dissipation factor was outside the range of the meter, but it was less than 0.001.

XHLR1l

The internal structure. I found this shape for the capacitor plates offered the best compromise between surface area and ease of construction.

After a successful test with a flyback transformer, I added the rest of the package of plates, for a total of 26 active plates. As I doubt that the lab is open on Sunday, I have not yet taken measurements on the new configuration. Extrapolation, however, gives 3.38 nF. Further testing was done with the larger capacitor. I resonated it with an air-core inductor for a few minutes, and it tolerated an estimated 8.5 kVA with no apparent damage. The test was stopped due to concern for my underpowered bipolar h-bridge.

It was also tested in a base driven spark gap coil.

JdUjk

No magnetically coupled primary makes construction simpler. Operation is similar to a magnifier coil.

67Q1zl

~2cm streamers were produced.

It probably would work better with a better RF ground and a larger capacitor and smaller inductor in the tank, for greater bang energy.

Ernie

Tue Aug 14 2012, 10:43AM

Registered Member #6129 Joined: Sun Aug 12 2012, 04:33AM
Location: somewhere downunder
Posts: 7

Hi everybody, I am new here, but have been reading this thread for sometime.
This interests me, as I am building a high speed Air gap flash, and wish to build a suitable Capacitor. This looks to be a very viable design.
The thread seems to have come to a sudden end, I am hoping it can be restarted.
How is petroleum jelly suited as a dialectric. Ernie

Conundrum

Tue Aug 14 2012, 05:43PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Maybe recycle copper leaf from dead LiPo cells?

just a thought, and it isn't hard to thin it using reverse electroplating.

-A

Ernie

Tue Aug 14 2012, 09:51PM

Registered Member #6129 Joined: Sun Aug 12 2012, 04:33AM
Location: somewhere downunder
Posts: 7

Yes there are many possibilities out there I should imagine.
I have had a look at a few different plates, but one in particular is a 180mm square one, which I have on order.
I have been looking at several types, and, there is one thing that has not been mentioned, and that is the fact that because you are putting one plate inside the other, they do not fit perfectly, in fact they leave a void. Though it is minuscule it is still there to cause problems, and as you put weight on them you spread this void to the sides. I think that for this to work properly this void should be filled. What thoughts on this. the best method needs to be found. Ernie

Ernie

Fri Aug 17 2012, 12:46AM

Registered Member #6129 Joined: Sun Aug 12 2012, 04:33AM
Location: somewhere downunder
Posts: 7

Ok, it seems as though the interest has gone from this thread, but I will keep trying, and add my findings.
The plates arrived they seem to be very sturdy without being overly thick.
The foil area is 5inch (127mm) square, I put four plates together and got a reading of .88n, but under some pressure this went up to 1.10n.
So I then tried coating this with petroleum jelly, and wow the capacitance dropped to .28n and no amount of pressure would change it, so four plates ended up in the trash can.
So it looks as though the dialect needs to be fairly thin, would a thicker foil make a difference, any ideas anyone.
For my project I don't really want to go to bigger plates, so at this rate I would need something like 120 plates, still not a huge size, and definitely a lot cheaper than a commercially made one.
I hope someone will help me here, I have some foil adhesive tape, it is conductive on one side but not the other, does it need to be on both sides to work properly. Ernie

brandon3055

Fri Aug 17 2012, 01:17AM

Registered Member #4548 Joined: Mon Apr 23 2012, 03:52AM
Location: tasmania
Posts: 271

No the thickness of the foil won't make much difference and the foil tape might work but the overlap between each price could be a problem

If I were you I would make a few small capes with different numbers of plates and test them to see how many plates per foil you need

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