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Registered Member #61569
Joined: Sat Apr 15 2017, 05:12PM
Location: Germany
Posts: 28
Well, i also rounded the edges but furthermore the entire transformer is emerged in shell diala x3 and degased in a vacuum for 10 hours. If you are interested i can post some pictures in the next few days. The transformer is made for a voltage multiplier and so far it is working great.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
I vacuum encapsulated all of my secondary coils in epoxy, and I shielded them from the ferrite core with some copper foil. They seemed to work when I briefly tested them, but I haven't really run any of them for a long time.
I take it that the failures you experienced happened before you put the transformer in oil?
Flachzange wrote ...
Well, i also rounded the edges but furthermore the entire transformer is emerged in shell diala x3 and degased in a vacuum for 10 hours. If you are interested i can post some pictures in the next few days. The transformer is made for a voltage multiplier and so far it is working great.
Registered Member #61569
Joined: Sat Apr 15 2017, 05:12PM
Location: Germany
Posts: 28
Hi, here are the promised pictures of the first transformer that i build. The housing is not that great and i am just going to finish the second one that should perform better.
On the first picture you can see the bobbin which is machined from Teflon. It has a 30mm hole in the middle for the ferrite core (100mmx27mmx27mm and the corners are rounded). The individual sections are not cut to the same depth. The first one is the deepest, and the last one on the left the flattest. This is also the high voltage side of the winding. Therefore the distance to the core is bigger and the electric field stress is reduced. Additionally the parasitic capacities are reduced which is also achieved by the winding in these sections. To get the wire from one section to another i have just sawed a small groove diagonally in the walls between the sections.
On the second picture the transformer is shown in the aluminium housing filled with diala x3. The left copper sphere is the high voltage output and the sphere on the top of the picture is grounded to act as a safety gap.
The third picture shows the multiplier arranged for an output of 300kV. I have used this multiplier with 8 Stages up to 750kV however corona discharges get a major issue (Even with 1m toroids). the multiplier on the picture works corona free up to 250kV then i get discharges from the small toroid on the upper right.
Registered Member #1321
Joined: Sat Feb 16 2008, 03:22AM
Location:
Posts: 843
Nice project you've got there.
As per the picture Patrick linked to, I put intermediate grooves in the bobbin to try to keep the wire away from the "sides" of the windings. So once one section is complete, the wire goes from the top of that section through a vertical slot and down to the bottom of the intermediate groove, then after a few turns the wire goes through another vertical slot and is introduced at the bottom of the next winding section, and so on.
All I wanted out of my coils was 12.5 kv peak. I think if I needed 50 kv peak (or more) I might try to use an air core transformer.
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Bobbin material rating DC vs AC voltage
