Inductor polarity?

Bah, we see all sorts of nonsense. The other day I saw a circuit diagram with polarity dots at *both* ends of the *same* transformer winding, and none for the other.

Jeroen Belleman

Oh. I think one of the dots migrated to the wrong side.

Was it a power component intended for line operation? Some of these have built-in fusing and the dot indicates the fuse end, which should be connected to the incoming line side.

It might semi-usefully indicate the N pole in a DC-bias situation. In some old TV circuits, a biased inductor (with a permanent magnet) was used. Otherwise, it's just a relic from a different design requirement (perhaps to make coupled inductors by positioning or by applying a winding later).

Antistatic markings on a package of nuts and bolts, same kind of relic.

So manufacturing doesn't pester engineering about which way to load the part?

So the magnetic field isn't reversed?

For a wounded coil you have an inner winding turning into outside windings. Normally in a switching environment you have a heavyly switching node and the other side is much less noisy. So yes, inductors, as wound foil or electrolyt capacitors have a polarity.

Bye

is it shielded?

snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:

This one has merit, Most of them sit on square pads and are a short barrel shape core, and especially true if the part only has (connected)pads on one edge of that square pad.

It is in the Z axis, silly man.

But let's say it was oh... MELF package. Do you think it flips the N and S if you flip the inductor end for end on the mount?

Nope. Wire, nail, battery. Field ONLY flips if battery is flipped. Flip the nail and North remains on the same side it was before the nail flip. Flip the leads and regardless of initial nail position the pole flips.

Ooh... oooh... I know one... So you don't get them wrong when putting them in series or parallel. Hehehe Nope!

Turns direction matters in such cases... (not here though, only within the same core field)

If you swap the pads you get to choosde positive or negative Z direction, that may matter for some applications.

if it's layered start or end will have different E field effects.

If Z axis and putting them in parallel you'll get weak positive or negative coupling depening if they oppose or not.

huh?

Unshielded drum cores leak a lot of H field, or pick up fields. A nearby pair can be connected so that the coupling cancels far-field. But you've got to get the polarities right. It is a niche application.

Yes, I was going to say that. We wind our own power inductors in a large-ish buck converter and the switch node is connected to the inductor end that is on the inside (start) winding and the outside (finish) is on the outside which is connected to the filter capacitor.

Keeps the noise emanating from the inductors to a minimum.

John Larkin Basically said this same kind of thing.

Well, I'm guilty of incomplete information. Sorry. No, it not intended for line operation. It is for a low power buck PS.

On the development board I have, the dotted end is going to the load and the other end goes to the switch. So I will do the same on my board.

Thanks, Uwe.

Yes. It is a TDK SLF10145 type.

It /may/ be useful if you have some close to each other, for example using two smaller inductors instead of a bigger one for reasons of space or form factor. It may not, but it's free.

Winding start, would be inside or outside?

They don't say. In my past life, a dot would indicate the start of the winding.

One possiblity is it has a bias magnet in it which allows it to operate at higher current in the intended direction before saturation sets in.

Jon

Thanks, Jon, but it does not have such a thing.