Does the inductor magnetic field effect the nearby components?? - Page 1
Forum section: electronics / beginners

author: Adhith
author_rank: Frequent Contributor
timestamp: July 24, 2018, 07:38:18 am
content: Hello everyone...I'm using a pi type filter using 470MH inductor and two1000mf caps on both side. However this circuit is placed near an amplifier board within my project enclosure. So my question is, Since the energy in inductor is store in form of magnetic field does this magnetic field has any effect on the near by components in the amplifier board or its totally safe to place the inductor near it??

author: Adhith
author_rank: Frequent Contributor
timestamp: July 24, 2018, 01:59:41 pm
content: Quote from: blueskull on July 24, 2018, 07:42:35 amThank you very much Sir for your help. I'm using a Small Toroidal inductor for the purpose. The components near to the inductor are some resistors and if I'm planning to shield the inductor then what could the possible material for it?? Do tapes work?? right now I have some insulation tapes, pvc tapes, kepton tapes and also have some thin glass fibre sheets too.

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 24, 2018, 02:20:38 pm
content: you have to use conductive material for shielding, plastic whatsoever won't do the job. there special shielding boxes which are solderable - but just this alone won't do it either; you have to lay out the pcb appropriatelly for good shielding results; just packing a toroid in a shielding box will not do it

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 24, 2018, 04:24:05 pm
content: The type of inductor will also have an effect on the amount of adjacent component interference. Torroids generally keep their fields more contained. You often want to put the inductors at right angles to each other as well. The ARRL Handbook covers these topics quite a bit, as many radio and amplifiers contain these larger components.Even adjacent traces can cause mutual inductance.https://www.electronics-tutorials.ws/inductor/mutual-inductance.htmlhttps://pdfserv.maximintegrated.com/en/an/AN4636.pdf

author: schmitt trigger
author_rank: Super Contributor
timestamp: July 24, 2018, 04:35:35 pm
content: There are several core forms specifically designed for low field radiation. Pot cores and toroids immediately come to mind.So by choosing a toroid, you have correctly selected a good core shape.A simple trick to visualize stray fields is to obtain very fine iron powder. On you inductor under test, apply the rated DC current with the aid of a laboratory supply.Place the inductor on the iron powder. Any material that sticks to it are because of stray fields.De energize the core in a separate area, and weigh the amount of iron powder that was attracted to it.Then compare a different core.This is only a qualitative test, but can help you visualize the relative amount of stray fields. For EI-cores, it is surprising the amount of material which is attracted to the gap.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 25, 2018, 01:51:06 am
content: Quote from: HB9EVI on July 24, 2018, 02:20:38 pmNot only conductive, but definitely metallic! Magnetic shielding is achieved by providing a preferred path (of higher permeability) to the magnetic field, so Al:ok, Fe:better Hiperm/Mu-Metall: best.

author: Adhith
author_rank: Frequent Contributor
timestamp: July 25, 2018, 08:03:42 am
content: Quote from: HB9EVI on July 24, 2018, 02:20:38 pmThank you for your reply sir. I was under the assumption that non conductive materials are usually used to the prevent the penetration of magnetic field since a pair of bar magnets are often separated by a piece of wood.

author: Adhith
author_rank: Frequent Contributor
timestamp: July 25, 2018, 08:05:37 am
content: Quote from: FlyingHacker on July 24, 2018, 04:24:05 pmThank you for your help Sir. I'll read the article that you have suggested to have a better idea.

author: Adhith
author_rank: Frequent Contributor
timestamp: July 25, 2018, 08:09:14 am
content: Quote from: schmitt trigger on July 24, 2018, 04:35:35 pmThank you very much Sir for your valuable reply. however the pi filter is already made and the caps are soldered to it as well. So I guess i cant do this experiment. However I'll conduct a similar test with another inductor in my shelf to see the results.

author: Neomys Sapiens
author_rank: Super Contributor
timestamp: July 26, 2018, 10:42:15 pm
content: About which frequencies are we talking here? I assume from your filter values that it is DC cleanup from mains ripple and other smut.I had to redesign a power amplifier for instumentation which suffered from magnetic stray fields.The guy who did it originally had thought that using a toroid transformer, whose main advantage is generally said to be it's low stray field, was already enough of a precaution.I rearranged the elements within and threw out the aluminium chassis mounting plate and had one of steel made. I placed the transformer below and made sure that above it was only the low-impedance part.Zhe effects were gone without a trace and I hadn't touched the circuit or PCB.