Magnetics

Magnetics covers transformers and inductors

• https://coefs.uncc.edu/mnoras/files/2013/03/Transformer-and-Inductor-Design-Handbook_Chapter_2.pdf
• https://coefs.uncc.edu/mnoras/files/2013/03/Transformer-and-Inductor-Design-Handbook_Chapter_5.pdf
• https://www.youtube.com/watch?v=xA8HalLJ92c
• https://training.ti.com/understanding-basics-flyback-converter
• https://www.youtube.com/user/katkimshow/videos

Transformer

These are just a pain to understand

Larger transformers increase hysteresis loss.

The correct frequency is critical. Ideally, the frequency should be as low as possible without saturating the transformer. Higher frequency increases hysteresis loss.

Materials

• Laminated Iron Alloyws: 1.5-2.0T 50Hz-1KHz
• Powdered Iron: 0.6-0.8T 1KHz - 100KHz
• Ferrites: 0.25-0.5T 20KHz - 20MHz

Higher tesla is associated with higher core losses, but also higher saturation.

DIY Tests

• epoxy and magnetite
• epoxy and ferrite (Fe2O3)
• laminated steel plates
• plaster as binder

If I had access to a kiln I could try making soft ferrites by mixing Fe2O3 and ZnO and heating to 1500F.

Notes from "Transformer and Inductor Design Handbook"

1

Hysteresis produces core loss.

Two forces; magnetomotive force (mmf) and magnetizing force (H).

Units

• Magnetomotive: Gilberts
• Magnetizing: Gilberts/cm = Oersteds
• Flux Density: Gauss
• Resistance to flux: Reluctance

Magnetomotive Force

 mmf = 0.4πNI
 N: number of turns
 I: current

Magnetizing Force

 H = mmf / MPL
 MPL: magnetic path length

Flux Density

 B =μH
 μ: permeability of core