Inductor proximity effects? - Page 1
Forum section: electronics / beginners

author: TheDood
author_rank: Regular Contributor
timestamp: December 06, 2019, 12:15:45 pm
content: Quote from: Ian.M on December 06, 2019, 11:28:53 amIt was pointed out I start a new thread, thanks Ian, feel free to drop your any of your inductor knowledge here.Quote from: TheDood on December 06, 2019, 11:23:13 am

author: Zero999
author_rank: Super Contributor
timestamp: December 07, 2019, 05:10:26 pm
content: The coils have to be directly facing one another to ensure good coupling. If they're at 60 degrees, then there will hardly be any coupling. How the inductor is wound depends on how far the field extends. A toroidal inductor hardly leaks any flux, but a large pancake shaped inductor is much more leaky.

author: Neilm
author_rank: Super Contributor
timestamp: December 07, 2019, 07:20:11 pm
content: Some inductors are shielded so leak very little flux, others are open frame and can have some interesting issues (I did once have one of these couple to a power plane that really hit the efficiency). Could you post a few more details or a link to the original discussion so I could get some background?

author: TheDood
author_rank: Regular Contributor
timestamp: December 07, 2019, 08:37:47 pm
content: Thanks guys,I was trying to assess the effect on a rectified AC capacitive dropper waveform after flowing it through 2 identical common mode chokes wired in parallel. Both with an individually lower current rating than the total cct current being flowed, though in parallel within their rated specs. I was trying to determine how proximity and orientation would effect the intended output waveform. I was hoping that I could orient in a position in such a way that the field lines wouldn't cancel, but compound (if anything), but I've read that inductors in parallel reduce total inductance, so I'm just not sure I'm comprehending (it seems the equation doesn't have any variables for proximity or orientation, the things I thought would have the greatest impact on inductance). I figured if I could determine the most favorable positions and/or why, that I'd be able to then orient inversely for a minimal interaction.When I simulate inductors in parallel in LTspice, it seems the program accounts for proximity. The closer I place the parallel inductors to each other, the less filtering I notice. I've run some simulations and used 100mH as my inductor size, but I've only 0.35A rated inductors and the cct sim was for 0.5A, so thus what sparked my question.Also, I'm curious about EMI? If I were designing an RC car or drone, what kind of shielding or proximity to antennas ect should I be aware of? If the Hz of the waveform going into the inductor is different than the radio frequency used for wireless commands, I shouldn't have interaction, or should I? What signals are most susceptible to inductor noise, or maybe there isn't a generic correlation to be had? Can you wrap an inductor in aluminium foil and mitigate EMI? Will inductors induce a charge inside capacitors if placed within close proximity?EDIT:Link to original thread...https://www.eevblog.com/forum/beginners/bypassing-loads-under-constant-current-efficiently/

author: radiolistener
author_rank: Super Contributor
timestamp: December 08, 2019, 11:05:10 pm
content: In order to reduce coupling between two inductors, you're needs to place them at 90 degree to each other.In order to reduce parasitic resonances of inductor, the coil turns should be evenly distributed along the length.The best parameters can be achieved when coil diameter is equals to the coil length.Use wire from high purity copper with no chemical additives to get better Q-factor.Use low loss RF isolators for the coil frame.