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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: squeezing a field
Date: Wed, 23 Oct 2024 18:14:57 -0000 (UTC)
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john larkin <jl@glen--canyon.com> wrote:
> I'm designing a small PCB with essentially 5 sync buck switching
> regulators. Board space is tight so I want to put the inductors on the
> bottom of the multilayer board. There's a 0.2" gap between the bottom
> of the board and a big aluminum flange.
> 
> Unshielded drum cores have the most energy storage per volume or
> dollars. They store energy in the universe instead of in ferrite. Good
> cooling too.
> 
> Something like this just fits
> 
> https://www.digikey.com/en/products/detail/bourns-inc/SRN8040TA-470M/6155133
> 
> Its mag field lines will bounce off the PCB planes and the flange,
> change from the classic bar magnet pattern into a pancake . I wonder
> what that will do to its electrical behavior. 
> 
> 
> 

Not a whole lot.  In the near-field region, B obeys Laplace’s equation,
which means among other things that the field falls off on the length scale
of the gap, not of the whole inductor. 

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  
ElectroOptical Innovations LLC / Hobbs ElectroOptics  Optics,
Electro-optics, Photonics, Analog Electronics