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Winding Ferrite Tranformers Similar to Tesla Coils

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Patrick

Sat Jan 11 2020, 12:24AM

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

Tesla coils are wound nice and neat from there low voltage end to their HV top load. Ive built a winding machine.

Instead of using the traditional "pie winding" method on plastic bobbin, is it possible to wind continuously from top to bottom and keep one end grounded such that the insulating ability would be similar to a Tesla tube and "pie winding" but without the annoying grooves , yet still having the same insulating value ?

I also plan to vacuum fill with epoxy, the whole thing at 400 Microns. The insulation will be layers of epoxy-kapton-Electrical Paper of several layers on all side between the bobbin and the primary/ferrite.

It will have a calculated insulation value of 80kv in all directions, a de-rated value of 50kv and a real running voltage of 30kv.

Flachzange

Sat Jan 11 2020, 03:25PM

Registered Member #61569 Joined: Sat Apr 15 2017, 05:12PM
Location: Germany
Posts: 28

We have build a ferrite transformer very similar to the method you have mentioned.
It does not have the same insulation performance like a tesla coil, since the ferrite core is grounded. But in terms of the insulating voltage between the individual winds it is the best method.
Here is the link to the youtube:

jpsmith123

Sun Jan 12 2020, 12:59AM

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

Wow nice work. I want that ferrite core; no doubt Patrick wants it too.

What kind of peak output voltage are you getting and at what frequency?

Also do I assume correctly that the nylon wire tie on the lathe chuck is part of some kind of an optical turns counting system? If so what does the rest of the turns counting system consist of?

Flachzange

Sun Jan 12 2020, 12:14PM

Registered Member #61569 Joined: Sat Apr 15 2017, 05:12PM
Location: Germany
Posts: 28

Thank you very much!
Unfortunatly we only get to 70 kV of peak output voltage at 7 kHz.
If we increase the frequency the output voltage will decrease. And by lowering the frequency the core gets into saturation.
Our aim is 100 kV output voltage in order to feed out voltage multiplier.

Correctly, the cable tie is for counting, not optical but "mechanical". It hits the mouse and it adds +1 in the microsoft calculator

Patrick

Sun Jan 12 2020, 08:54PM

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

Flachzange wrote ...

Correctly, the cable tie is for counting, not optical but "mechanical". It hits the mouse and it adds +1 in the microsoft calculator

Stunningly clever !

Was that box vacuum oil drawn ? Im going to do both a transformer out of oil and one out of epoxy and compare the insulating results. I worry about heat and pressure changes causing leaks out of a liquid system.

klugesmith

Mon Jan 13 2020, 05:10PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Nice work!
The handy turns counter prompted me to upload an old video with mechanical turns counting.
It's about a sense coil made for a 3 inch (76 mm) solid electromagnet pole.
I hope the link works. First youtube for me in many years.

Patrick

Tue Jan 14 2020, 09:13PM

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

Is multilayer insulation of different types that averages out to be 500 V/mil better than solid insulation which is 500 V/mil ?

2Spoons

Wed Jan 15 2020, 03:47AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

It can be better. With multilayer insulation you are unlikely to get defects aligned between layers, whereas a defect in a single layer can compromise your insulation quite badly.

Patrick

Wed Jan 15 2020, 04:31AM

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

It seems epoxy sticks to kapton. I want to use electrical paper, oil and kapton film. ill vacuum dry and draw the oil into its container, but i worry about temperature causing pressure changes. i want to use milled plastic pipe and thick plastic sheet, but worry about needing a relief valve or something for temperature or altitude change ...

proud mary suggested a bourdon tube from a barometer but i dont know how much expansion is needed. Also i was thinking of a gas ballonet like in a helium zeppelin or balloon.

The gas ballonet surrounded by oil would be easily compressed. since gas is easily compressed the oil would stay at a constant pressure while the ballonet shrinks or expands. It would be a passive system and the envelope size could be chosen for the needed oil volume.

am i crazy ?

klugesmith

Wed Jan 15 2020, 08:55PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

Rubber bladder to accommodate thermal expansion of oil is common.
How about rubber bulb from an eyedropper, or for honking a horn, or part of a rubber glove?

Need to mind the material compatibility of oil and elastomer. It's not too soon to start soaking some samples to see what happens.

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