Re: inductor polarity

On Fri, 28 Feb 2025 09:03:06 +0100, Arie de Muijnck <noreply@ademu.nl>
wrote:

On 2025-02-28 04:50, john larkin wrote:

I need to put 16 of these on a very dense PC board.
 
https://www.digikey.com/en/products/detail/murata-power-solutions-inc/19R476C/5798223
 
Each of the eight channels needs two of these. If I can put each pair
of inductors close together and with the same current but opposed
field direction, I'll get minimum mag field leakage to other channels
(and to other boards.)
 
I see that one lead is longer than the other. I wonder if that implies
a consistent winding direction, so my manufacturing people could use
that as the "pin1" indicator.
 
If that's not dependable, I'll have to set up a rig to determine mag
field polarity, and mark one side with a red dot or something.
 
I'd rather use surface-mount shielded inductors, but these tall
unshielded drum cores have way more L and less R than a shielded part,
for a given PCB footprint.
 

>
It works fine, but the total inductance will be somewhat higher than just 2x.

Even better! Any guess how much? I'll order some samples to play with.

The external field is way less, I use that trick in a sensitive environment (ADC's etc).
>
If you mount them parallel to the PCB, try alternating 90 degree positioning from pair to pair to minimize coupling.
>

I want to use all the available height and minimize PCB footprint, so
this is an ideal part. But there must be some other orientation that
miminizes coupling between inductor pairs.

The product is an 8-channel programmable dummy load module that
simuates resistance and inductance, to pretend to be a solenoid or a
motor winding, so low-level crosstalk won't get noticed.