Magnetics Fundamentals (for non-specialists)

You don't need a physics degree to be useful here, but a simple mental model of how magnetics behaves makes the product — and our customers' problems — click. Here's the plain version.

1. Fields, flux, and the magnetic "circuit"

A current makes a magnetic field. Coil the wire and the fields add up — more turns, more field.
A magnetic core (iron, ferrite) is a highway that carries this field easily and concentrates it.
The total field flowing through the core is called flux — think of it like current flowing in a wire.
How easily a material carries flux is its permeability; the opposition to flux is reluctance (the magnetic version of electrical resistance). High permeability = low reluctance = flux flows easily.

2. Everything tries to minimize energy

This one idea explains a lot: - A magnetic system settles into the lowest-energy state it can reach. - So flux takes the easiest path (least reluctance), and forces appear that pull parts toward lower-energy arrangements. An iron slug is pulled into a coil, and an air gap "wants" to close, because both lower the stored energy. - That's where magnetic force comes from. Motors, actuators, and relays are just this principle harnessed.

3. Where the losses come from

Losses = energy turned into unwanted heat. Two big families.

Core losses (in the magnetic material)

They grow with frequency and with how hard you swing the flux: - Hysteresis loss — every AC cycle the material's magnetization flips direction; the "stickiness" of that flipping wastes a bit of energy each cycle. - Eddy-current loss — the changing field induces little circulating currents inside the conductive core, which heat it up.

How we cut core losses: - Laminations — build the core from thin, insulated steel sheets. The thin insulated layers break up the eddy-current loops so they can't circulate freely. Thinner laminations → less eddy loss (needed at higher frequency). - Powder cores / ferrite — make the core from tiny magnetic particles insulated from each other (encapsulated powder), or from ferrite (a magnetic but electrically insulating ceramic). Insulating the particles stops large eddy currents forming. This is why high-frequency magnetics use ferrite or powder cores instead of solid steel.

Winding (copper) losses (in the conductors)

DC resistance — plain I²R heating.
Skin effect — at AC, a conductor's own changing field pushes current toward its outer "skin," so the usable cross-section shrinks and resistance rises with frequency.
Proximity effect — the magnetic field from neighbouring conductors and winding layers shoves current into uneven patterns inside a conductor, adding more loss. In multi-layer windings this often dominates.

How we cut winding losses: - Litz wire — many thin strands, each individually insulated and woven (transposed) so every strand spends equal time on the inside and outside of the bundle. Thin strands beat skin effect; the weave averages out proximity effect. That's the whole reason litz exists. - Smarter winding geometry: fewer/thinner layers, interleaving windings, and keeping conductors out of strong local fields.

4. Internal vs external fields (why proximity matters)

A conductor feels two magnetic fields: - its own field → causes skin effect; - the field from everything around it (other turns, other layers, the air gap) → causes proximity effect.

Near a core's air gap the external "fringing" field is strong, so any copper sitting there loses a lot. Good design keeps conductors away from those hot field regions.

5. A few terms you'll hear

Saturation — push too much flux and the core "fills up"; permeability collapses and inductance drops. Designs avoid saturating.
Air gap — a deliberate gap lets an inductor store more energy before saturating, at the cost of a strong local fringing field near the gap.
Inductance — how much magnetic energy a winding stores for a given current. Leakage inductance is the part of the field that doesn't couple between windings.

Want more depth on any of these? Add it here — this page is meant to grow.