Clemente Figuera Discussion and Opinions

[feb_]

magnetic field strength B = 216.2 mT: input and output.

input: 0.576 mW.
  Electromagnet with 24 Turns.pdf (Size: 123.93 KB / Downloads: 24)

output: 60.31 W.
  System to Deliver 24 V Output.pdf (Size: 183.41 KB / Downloads: 24)

Wires perpendicular to magnetic field.

[feb_]

Design of Two Electromagnets with 0.4 mm Wire at
100 kHz with Resonance and 8 Output Wires

Is >2000% losses reasonable?
That's what you need to make it underunity.


  Two Electromagnets 8 Output Wires.pdf (Size: 135.11 KB / Downloads: 24)

  Resonance at 100 kHz.pdf (Size: 129.99 KB / Downloads: 17)

  8 Output Wires at 100 kHz.pdf (Size: 109.84 KB / Downloads: 22)

[feb_]

https://en.wikipedia.org/wiki/Electromagnet

"At any air gaps (G) between core sections, the magnetic field lines are no longer confined by the core. Here, they bulge out beyond the core geometry over the length of the gap, reducing the field strength in the gap.[2] The "bulges" (BF) are called fringing fields.[2] However, as long as the length of the gap is smaller than the cross-section dimensions of the core, the field in the gap will be approximately the same as in the core."

[feb_]

That was the theory, let's see if it works in practice.
By trying to build something similar.

   

U ferrite N87
https://eu.mouser.com/ProductDetail/EPCO...40OS4wLjA.

   


  butterfly 8 coil hold.stl.zip (Size: 4.56 KB / Downloads: 6)

  core hold.stl.zip (Size: 954 bytes / Downloads: 3)

   

Picture from coil test no capacitor no resonance,
just verifying that butterfly 8 coil works.

[Sandy]

Nice! Please share your experimental results! Thanks, Sandy

[feb_]

With  U cores you use both sides of the electromagnets and get twice the output.

   

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I might need some help with resonance, haven't been doing it, need to try to get into it.
So suggestions are welcome. How do I get resonance in the best way?
Do I need an LCR meter? What type of capacitors is best?
How to generate the sine wave with sufficient strength?

[Sandy]

LCR is helpful. If you have oscilloscope you can do the following... by eye I would guess that your coils will only need a few nano farads or less to resonate at 100khz. Possibly there is too much inductance for the coils to resonate at 100khz.
Without LCR meter. Get a nano farad cap of known value. If you have one, hook it in parallel with coil. Place scope probes across cap. Hook negative of PSU or battery to one side of cap. Set oscilloscope to single capture with appropriate trigger level. Tap positive of PSU on other side of cap. Now look at scope trace and zoom in on the oscillation ring down. Use oscilloscope frequency measurements to determine frequency. Use online resonance frequency calculator or AI to enter F and C and determine L. Low esr caps are good (not electrolytic).
Tune for resonance by adding/subtracting turns or capacitance until maximum voltage amplitude is found. Or if you don't need exactly 100khz then adjust frequency until Max V amplitude is found. That's how I do it. There is probably better ways...
For sine wave...
Some people use function generator output directly if it can handle the impedence (power is limited, though).
Probably easiest way is to feed square wave from H bridge module and microcontroller. Use AI to write code, minimal skill required.
Others here with more knowledge than me will hopefully chime in.
Happy experimenting!