Author Topic: Staggered 50uH and 250uH inductor design for LISN  (Read 41808 times)

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Offline slloyd

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #150 on: July 15, 2018, 11:36:10 pm »
Quote
The inductance L2 should have a Q-factor not less than 10 over the 9 KHz to 150 kHz frequency range. In practice, it is advantageous to use inductors coupled in series  opposition in the live and neutral lines (common-core choke)

when i read that, i think that there should be ONE 250uH spool.. with two windings on it.  one wound clockwise and the other counterclockwise 

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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #151 on: July 16, 2018, 09:40:19 am »
thats the third solution I have seen to the 250uH inductor

air cores
common mode opposed winding air core
regular common mode choke wound on ferrite/iron
 

Offline slloyd

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #152 on: July 16, 2018, 03:10:17 pm »
"common mode opposed winding air core"  i think this is what i'm talking about.  it comes from CISPR 16
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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #153 on: July 17, 2018, 03:08:46 am »
can someone post cisper 16

nmv found it

but wtf its some old ass indian standard. is it still relevant?

Also if you read research papers about inductors, they say a better solution is to put a RL in parallel with the L, rather then using just a R, since the R is kind of a RF shunt, and the extra L works as choke, but then you have mutual inductance between the two L's.

I already superglued a bunch of shit together and I forgot about the chassis so either I need to make the chassis really big or live with like a 45 uH LISN. I am also not modding or rewinding those big air inductors I made. Winding a giant air cored torroid like you say would just be way too much of a pain in the ass, I almost had a fit trying to wind that thick wire in 2 layers on my massive bobbins I made of PVC pipe and wood.

Its not easy. I had to wind a few layers of wire, use dowels/hammers to hammer the windings tight, glue, repeat... even winding it was difficult because its so thick, the best way I found was to screw the inductor to a table and walk around it in a circle pulling on it like I am trying to pull someone out of a cave. Then when you need to do the second layer you need to make a special dowel rod thing to beat the wire down neatly.

Can someone with a RF simulator do some explanations here? I think we need field solver data.

How do you even make a big ring bobbin? You need a wood lathe and some skills. . the only other thing I thought of is to fill one of those doughnuts you sit on after ass surgery or maybe some kind of tiny life preserver or something with concrete or maybe expansion foam, then coat it in hard resin/fiber glass. I guess you can just use a donut slice by gluing together a buncha ply wood you hit with a hole saw but that would make a curved rectangular inductor... given how hard it is to wind something big you might as well try to go for a ring. Maybe paper mache could work too if you can make a ring out of chicken wire. I do NOT want to file that kind of monstrocity. One unsafe ass way that comes to mind is to use a chain saw or use on of those super unsafe angle grinder disks that has a chain saw chain wrapped around it.

I would really like to see a simulation or more information before I fuck with that kind of pain in the ass shit though.

If you use a magnetic torroid then you can either have it work as a matched DM choke (where you wrap the wires together) or a kinda mixed choke that has some DM and some CM by winding it on opposite sides like a classical transformer.
« Last Edit: July 17, 2018, 03:29:15 am by CopperCone »
 

Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #154 on: July 17, 2018, 03:31:16 am »


One of these?
 

Offline dazz1

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #155 on: July 17, 2018, 06:40:42 am »
Hi
I agree with slloyd's interpretation.  That the series coil(s) are coupled.  That the coil on the line is counter wound to the coil on the neutral to minimise coupling.

Given that the current through line is the exact equal and opposite to the current through the neutral, does that mean that physically they are wound in the same direction?
or
Has the clause been incorrectly interpreted?
or
Does it really matter as long at it is in spec to the standards?

Some modelling would answer a few questions and help evaluate the different permutations.

Dazz
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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #156 on: July 17, 2018, 07:37:37 pm »
Can you make a MSPAINT sketch of the coil windings and the way they are connected to the mains because I getting very confused by talk of winding directions. I don't know what 'common opposition' or counterwound means.
« Last Edit: July 17, 2018, 07:45:10 pm by CopperCone »
 

Offline dazz1

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #157 on: July 17, 2018, 08:29:35 pm »
Hi
I haven't seen "common opposition" before but it most likely means 2 coils wound on the same former in different directions, like left hand and right hand thread.
To me, "counter-wound" means the same thing, but not necessarily on the same former.

The purpose is usually to null the net magnetic field. Wire-wound resistors are often wound this way to minimize mutual inductance with other components.

The same effect can be achieved with two coils wound in the same direction, but the current in one flowing the opposite to the other.    This is what I would expect to see in a typical LISN

The other way to minimize mutual inductance between coils is to mount the coils at a specific angle to each other.  From memory it is about 53 degrees but I can't find a reference so don't rely on that figure.

Dazz


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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #158 on: July 17, 2018, 09:45:10 pm »
Should the former be a torroid or cylindrical?
 

Offline 2N3055

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #159 on: July 17, 2018, 10:13:06 pm »
It seems to me L1 and L2 are simple common mode chokes..
 

Offline Jay_Diddy_B

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #160 on: July 17, 2018, 10:29:44 pm »
Hi,

The 250uH are not coupled in anyway. They are independent inductors. Have a look at Dave's teardown of the tekbox LISN.

Link: https://www.eevblog.com/forum/blog/eevblog-994-mailbag/

The 50uH inductors are horizontal and the 250uH inductors are vertical.

The primary purpose of the 50uH inductors is to define the impedance of the LISN. The primary purpose of the 250uH inductors is an EMI filter to stop noise from the line side appearing on the output.

If the inductors are coupled they would be shown on the schematic L1a, L1b. They are shown with different designations on most schematics.

Regards,

Jay_Diddy_B
 
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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #161 on: July 17, 2018, 11:05:52 pm »
yea but we got pictures of LISN that have the 250uH inductors on transformer cores and the indian document seems to say common mode too

I wanna know whats going on exactly before I buy parts to finish the LISN. This project is in development hell right now, I don't want to make a enclosure or design a coupler/protection anymore.
« Last Edit: July 17, 2018, 11:09:35 pm by CopperCone »
 

Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #162 on: July 17, 2018, 11:07:03 pm »
It seems to me L1 and L2 are simple common mode chokes..

You mean that L1 and L2 are a common mode choke? How could you have two common mode chokes? It should be L1 only not L1 L2.

I think maybe the enclosure happens to turn it into a something kinda like a common mode choke.

I built mine on a plank of wood that screws into a chassis since all the parts are big, so I figure I can test it out side on a table connected to a VNA some how to see the exact influence of the chassis on the circuit. Right now my prototype is built so there is a single strip of aluminum sheet to act as a ground plane and it goes between everything, so the inductors are basically off the ground plane.
« Last Edit: July 17, 2018, 11:13:08 pm by CopperCone »
 

Offline 2N3055

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #163 on: July 18, 2018, 12:27:28 am »
L1 are two separate coils.. With as little coupled -inductance as possible..

L2 is a common mode choke .

quote : "In the frequency range from 9 kHz to 150 kHz the
inductance L2 should have a Q-factor not less than 10. The
inductors L2 are coupled inductors, forming a common-
core choke in order to block the common mode EMI."

Source : "Building a Low Cost Line Impedance Stabilization Network for EMI Tests".
 

Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #164 on: July 18, 2018, 12:36:25 am »
So why did the tekbox use non coupled seperate inductors?
 

Offline 2N3055

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #165 on: July 18, 2018, 08:01:35 am »
So why did the tekbox use non coupled seperate inductors?

CISPR 16.1.2 suggests it as a better solution but does not mandate it.

Truth is, that means that it can be wound up on toroidal core. Differential cancelation of magnetic field will make sure core is not saturated easily, and maybe a ready made common mode choke could be used, provided it will have required characteristics.
 

Offline dazz1

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #166 on: July 18, 2018, 12:26:02 pm »
Hi
I am looking at this and thinking that the spec is quite broad and technically relatively undemanding.  The "best" solution is the one that meets the standard.  There are multiple "best" solutions.
I wouldn't expect CISPR to get into any detail on protection because "their" argument would be that different regions have different requirements. 

I think the best approach would be to bread board a design, then progress to PCBs and enclosures.  Maybe a dash of modelling before hand.

Dazz
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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #167 on: July 19, 2018, 01:21:56 am »
What would be a counterpart for the 5uH LISN in terms of EMI filter inductor? I am also working on a 5uH ISN and I thought that I should put 25uH inductors on it..

has anyone seen a 5uH ISN with 25uH inductors on it?
 

Offline 2N3055

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #168 on: July 19, 2018, 07:02:09 am »
What would be a counterpart for the 5uH LISN in terms of EMI filter inductor? I am also working on a 5uH ISN and I thought that I should put 25uH inductors on it..

has anyone seen a 5uH ISN with 25uH inductors on it?

If you going to feed it from good, clean PSU you don't even need one.

If you had really clean 230/240V AC you wouldn't need an 250uH either, at least in theory...
 

Offline T3sl4co1l

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #169 on: July 19, 2018, 01:38:11 pm »
I once made a 20MHz CDN, which used 1uH inductors followed by 1.2uH inductors.  The two-stage design was to afford more isolation between DC and EUT/RF ports, and more freedom from impedance mismatch (the LCL filter is well dampened with RCs).

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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #170 on: July 19, 2018, 06:57:27 pm »
schematic?

Also, is there a way to do both injection and LISN monitoring at the same time, to see if input emissions do funny things to emissions?
« Last Edit: July 19, 2018, 07:01:34 pm by CopperCone »
 

Offline slloyd

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #171 on: July 26, 2018, 03:52:46 am »
PCB's are on hand.  haven't ordered the parts yet.  enclosure is designed with all the necessary cut-outs. 

I'm just thinking about this 250uH inductor.. i know Tekbox and other examples show two separate coils.  not sure if one is wound right hand and other opposite or not.  but CISPR definitely implies they should be wound on the same former.  obviously it doesn't matter much since working examples have it as separate.  i just thought 'd ask before going through the pains of winding these things up.
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Offline charliedelta

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #172 on: July 28, 2018, 08:21:23 am »
Heres some pictures of Various manufacturers LISN's
« Last Edit: July 28, 2018, 08:22:58 am by charliedelta »
 
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Offline CopperConeTopic starter

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #173 on: July 28, 2018, 11:43:30 am »
What are those capacitors? They all look weird.
 

Offline T3sl4co1l

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Re: Staggered 50uH and 250uH inductor design for LISN
« Reply #174 on: July 28, 2018, 07:39:43 pm »
Just metal can film-in-oil.

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