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Antonio

Fri Feb 18 2011, 11:48PM

Registered Member #834 Joined: Tue Jun 12 2007, 10:57PM
Location: Brazil
Posts: 644

Layer by layer, with insulation. How will you interconnect the sections? If you pass a wire from the top of one winding to the bottom of the next you ruin the insulation. The classical way to do this is to interconnect the sections alternately at the top and at the bottom.

haxor5354

Sat Feb 19 2011, 01:57AM

Registered Member #2063 Joined: Sat Apr 04 2009, 03:16PM
Location: Toronto
Posts: 352

how can you tell if your core is saturating?

Adam Munich

Sat Feb 19 2011, 03:17AM

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

Antonio wrote ...

Layer by layer, with insulation. How will you interconnect the sections? If you pass a wire from the top of one winding to the bottom of the next you ruin the insulation. The classical way to do this is to interconnect the sections alternately at the top and at the bottom.

Ahh, I realized that, and see ho I used sheets of cardboard? I'm going to pass the wire in between those sheets.

Adam Munich

Sat Feb 19 2011, 07:23AM

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

So... this is going to take a while...

I got 5 layers done. Insulation between them is achieved with some grocery bag kraft paper; it should soak up the oil nicely.

These 5 layers take up about 50 mil. There's about 250 turns so far, so each segment could hold a max of about 1250 turns.

1250 x 4 segments, 5000T. This... could take a while.

50T per layer, so 75k / 50 = 1.5kv per layer. I'm doing conventional winding (no takeback) so the oiled kraft paper needs to hold up to 3,000 V min.

8 mil paper, so 8 mils of oil alone should hold up to 3480V, the paper should also increase that. (I'm not really sure how to figure this stuff out)

Sulaiman

Sat Feb 19 2011, 08:16AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141

I don't want to discourage you but as mentioned by Steve, the self-capacitance of the windings is significant, especially with the secondary that you are building because of the very large number of turns giving a very large inductance. (This is why your fbt will not give a large output at 85 kHz) I think you will be operating at audio frequencies which will become annoying.

If you adopt the split-diode approach (dc out only) by putting a suitably rated diode between each section of winding then you will be able to operate at much higher frequencies and the diode voltages automatically self-equalise to an extent. If you can add a capacitor for each section of winding/diode the balance will be even better.
Arrange it so that either end of the secondary can be 'ground' to enable positive OR negative eht for flexibility.

Ken M.

Sat Feb 19 2011, 05:30PM

Registered Member #618 Joined: Sat Mar 31 2007, 04:15AM
Location: Us-Great Lakes
Posts: 628

How exactly would one calculate a coil like this ones self capacitance, because I don't think the exact formula that is used to calc a tesla coils self c would work, since there are layers which I imagine would compound the self C.

Dr. ISOTOP

Sat Feb 19 2011, 05:59PM

Registered Member #2919 Joined: Fri Jun 11 2010, 06:30PM
Location: Cambridge, MA
Posts: 652

I suspect the calculation is far from straightforward; some numerical technique would probably be necessary.
Or you could just measure it

Adam Munich

Sat Feb 19 2011, 06:22PM

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

Self capacitance isn't really a big concern for me, as if this thing can put out 70kV it can operate on any frequency it pleases. It's goal is to drive an x-ray tube: hardly a difficult task. In fact noise could be a plus, kind of a warning signal.

My biggest concern is whether 8 mils of oil soaked kraft paper can stand up to the 3kV that'll be between each layer. I'm hesitant to continue adding layers until I figure that one out.

Hmm, anyone have a variable HV supply, a paper shopping bag, tinfoil and mineral oil? If you do, could you test the breakdown voltage of the oil soaked paper bag?

Adam Munich

Sat Feb 19 2011, 07:13PM

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

Hmm... I just tested this with a ZVS and uhh... this oil is conductive.

Let it be known that the oil inside projection TV lenses is not mineral oil.

Lolwut

Edit: Just tried it again, this time using vegetable oil. 1 layer of paper broke down at 4kVDC.
Gahh, looks like I'm rewinding it again. :-/

Hmm... I'm going to test bunch of materials first this time.

Edit2: Overhead transparency sheet is the way to go. My main concern is that it'll be hard to get the oil in the windings since it's not permeable. Solution is a sammich: Tissue paper, Plastic, Tissue paper.

I'm also going to put some in between those cardboard donuts.

Alex

Sun Feb 20 2011, 06:59AM

Geometrically Frustrated
Registered Member #6 Joined: Thu Feb 02 2006, 04:18AM
Location: Bowdoin, Maine
Posts: 373

I did some googling on this subject... The purpose of the fluid in a projection TV is to cool the phosphor in the image tube. It's just antifreeze (ethylene glycol) and water.

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