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Custom transformer calculation

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Eagle_85:
Another question:
How do i buy the the ferrite core the easiest way? Have someone make a custom core? And if so what company and how much will it cost? Or is it easier to buy some standard square and round pieces of ferrite and glue them together? And in that case what is a god source for standard ferrite pieces?

T3sl4co1l:
Ferrite can be ground, it's a soft ceramic.  Mfgs and suppliers offer grinding services, though usually for flat faces to meet a dimension or air gap, not sure about circular cuts.  If nothing else, a machinist would be able to figure something out.

https://www.digikey.com/product-detail/en/ferroxcube/UR64-40-20-3C90/1779-1461-ND/7651791
This is the sort of thing I was thinking about.  Just use two spools so the core doesn't have to spin.

Tim

poorchava:
If I understand correctly, there will be a gap between the rotating part and the C-shaped part. Introduction of a gap decreases Al quite badly, so you'll have to wind more turns to keep the idle current reasonable. Also unshielded gaps will tend to radiated noise like mad due to fringing field.

You could make it a flyback, but that requires that the gaps be absolutely stable so that the primary inductance doesn't go too low, as the gap increases.

Eagle_85:

--- Quote from: poorchava on August 19, 2020, 08:55:00 pm ---If I understand correctly, there will be a gap between the rotating part and the C-shaped part. Introduction of a gap decreases Al quite badly, so you'll have to wind more turns to keep the idle current reasonable. Also unshielded gaps will tend to radiated noise like mad due to fringing field.

You could make it a flyback, but that requires that the gaps be absolutely stable so that the primary inductance doesn't go too low, as the gap increases.

--- End quote ---

Yes it is probably better to rotate the bottom bobbin and not the core. So airgaps in the core can be eliminated. I just sketched it up in Fusion 360 pretty fast without thinking to much about it.

Is gluing ferrite pieces together an acceptable method of making a core? And if so what glue is best to use?

langwadt:
how about using a multicore cable to get more "turns" and just run it through two toroids?

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