Re: two drums

On Wed, 12 Mar 2025 11:25:30 +0100, Klaus Kragelund
<klauskvik@hotmail.com> wrote:

On 12-03-2025 03:35, john larkin wrote:

 
https://www.dropbox.com/scl/fo/qpfhkvbfig7elysx78lq3/ALGqgMaRq1tx8aIiN3p1TfM?rlkey=36bcqfdb9di22ko48j89vocut&dl=0
 
If I put two of these drum core inductors close together, and get the
phasing right, I get an extra 5 mH for free, without any more ESR. And
external mag fields drop too, I think.
 

>
Looks like they are cheak unshielded types. But anyway, nice to get more
indtance for free.

Ushielded drums are an unfortunate necessity here. Their specs greatly
exceed any shielded inductors that I can fit into the equivalent
volume. These Murata parts are tall and skinny, further optimizing my
use of PCB area.

There just aren't many inductors in the milliHenry range. All the cool
shielded surface mount things seem to stop at 1 mH. Audio transformers
are terrible as inductors.

>
When you put them in series, the SRF increases a little bit also.

Not an issue in this application. I'm simulating r+l loads like motors
and solenoids, pretty slow stuff.

A jet engine FADEC might drive over 200 relays, soldenoids, and torque
motors, DC on-off and PWM from maybe 5 to 30 KHz.

>
I would suggest you measure with a Bode 100 or equivalent, that crappy
LCR does not give you much info.

That's a classic, original AADE lc meter. I believe it in this range.
No L meter that reports a single number is really right, because
inductors are complex.

I cross-check L meters with a 50 ohm signal generator and a scope.
That finds L, ESR, SRF. Or I TDR the small stuff.

Inductors are by far the worse parts we use.