Reply by Jan Panteltje●November 13, 20152015-11-13
On a sunny day (Fri, 13 Nov 2015 14:36:59 -0000) it happened RBlack
<news@rblack01.plus.com> wrote in
<MPG.30b005e841428f7298968e@reader80.eternal-september.org>:
>On Fri, 13 Nov 2015 13:30:36 GMT, Jan Panteltje
>(pNaOnStPeAlMtje@yahoo.com) said:
>> On a sunny day (Fri, 13 Nov 2015 11:09:04 -0000) it happened RBlack
>> <news@rblack01.plus.com> wrote in
>> <MPG.30afd52fecf9b85498968d@reader80.eternal-september.org>:
>>
>> >OK, this is how I set up the test, two of the parts facing each other
>> >across a piece of (mostly) bare FR4:
>> >
>> >http://www.rblack01.plus.com/images/IMG_20151113_093946933.jpg
>> >http://www.rblack01.plus.com/images/IMG_20151113_093915919.jpg
>> >http://www.rblack01.plus.com/images/IMG_20151113_093930839.jpg
>> >
>> >(the holes on 0.1" pitch are not plated through)
>> >
>> >SMB connector to each one, I mirror-imaged everything to keep the E-
>> >field coupling down as best I could. One part connected to the spectrum
>> >analyser input, the other to the TG output, set to 0dBm.
>> >
>> >Results:
>> >
>> >100 kHz - 1 MHz :
>> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-lo.png
>> >1 - 10 MHz :
>> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-mid.png
>> >10 - 100 Mhz:
>> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-hi.png
>> >
>> >Not much to see at low frequencies, but a nasty big peak at 40ish MHz,
>> >which corresponds to the SRF of the part. We have a big, broad
>> >emissions peak at 65 MHz, I suppose the presence of the ground plane in
>> > real product could be shifting the resonance.
>>
>>
>> Nice pictures.
>>
>> The basic solution to prevent magnetic coupling is:
>> 'put the coils at right angles to each other'.
>> that would require a small extra rising PCB in this case.
>> But the second rule:
>> 'as far away from each other as possible'.
>> So why put these on opposite sides of the board?
>> As you mention adding a ground-plane it seems you are making a new layout.
>> In that case move the coils further away from each other.
>>
>>
>
>Yes, the parts were deliberately placed in the 'poorest' configuration.
>This was a test to see how magnetically 'leaky' this particular inductor
>design is. The answer seems to be 'very' - I will repeat the test on
>the replacement inductors proposed upthread, once I have samples of
>them.
Ha, my misunderstanding
Yes coupling coils this way makes a good rotary transformer,
say 2 potcore halves...
Reply by RBlack●November 13, 20152015-11-13
On Fri, 13 Nov 2015 13:30:36 GMT, Jan Panteltje
(pNaOnStPeAlMtje@yahoo.com) said:
> On a sunny day (Fri, 13 Nov 2015 11:09:04 -0000) it happened RBlack
> <news@rblack01.plus.com> wrote in
> <MPG.30afd52fecf9b85498968d@reader80.eternal-september.org>:
>
> >OK, this is how I set up the test, two of the parts facing each other
> >across a piece of (mostly) bare FR4:
> >
> >http://www.rblack01.plus.com/images/IMG_20151113_093946933.jpg
> >http://www.rblack01.plus.com/images/IMG_20151113_093915919.jpg
> >http://www.rblack01.plus.com/images/IMG_20151113_093930839.jpg
> >
> >(the holes on 0.1" pitch are not plated through)
> >
> >SMB connector to each one, I mirror-imaged everything to keep the E-
> >field coupling down as best I could. One part connected to the spectrum
> >analyser input, the other to the TG output, set to 0dBm.
> >
> >Results:
> >
> >100 kHz - 1 MHz :
> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-lo.png
> >1 - 10 MHz :
> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-mid.png
> >10 - 100 Mhz:
> >http://www.rblack01.plus.com/images/Inductor-leakage-spectrum-hi.png
> >
> >Not much to see at low frequencies, but a nasty big peak at 40ish MHz,
> >which corresponds to the SRF of the part. We have a big, broad
> >emissions peak at 65 MHz, I suppose the presence of the ground plane in
> > real product could be shifting the resonance.
>
>
> Nice pictures.
>
> The basic solution to prevent magnetic coupling is:
> 'put the coils at right angles to each other'.
> that would require a small extra rising PCB in this case.
> But the second rule:
> 'as far away from each other as possible'.
> So why put these on opposite sides of the board?
> As you mention adding a ground-plane it seems you are making a new layout.
> In that case move the coils further away from each other.
>
>
Yes, the parts were deliberately placed in the 'poorest' configuration.
This was a test to see how magnetically 'leaky' this particular inductor
design is. The answer seems to be 'very' - I will repeat the test on
the replacement inductors proposed upthread, once I have samples of
them.
Reply by Jan Panteltje●November 13, 20152015-11-13
On a sunny day (Fri, 13 Nov 2015 11:09:04 -0000) it happened RBlack
<news@rblack01.plus.com> wrote in
<MPG.30afd52fecf9b85498968d@reader80.eternal-september.org>:
Nice pictures.
The basic solution to prevent magnetic coupling is:
'put the coils at right angles to each other'.
that would require a small extra rising PCB in this case.
But the second rule:
'as far away from each other as possible'.
So why put these on opposite sides of the board?
As you mention adding a ground-plane it seems you are making a new layout.
In that case move the coils further away from each other.
Reply by RBlack●November 13, 20152015-11-13
On Wed, 11 Nov 2015 21:35:55 +0000, RBlack (news@rblack01.plus.com)
said:
> On Wed, 11 Nov 2015 07:42:29 -0800 (PST), dagmargoodboat@yahoo.com
> wrote:
> > On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
[snip]
> > > The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
> > > milliohms, in a cubic SMD package roughly 12mm on a side.
>
>
> >
> http://www.digikey.com/product-detail/en/7443320330/732-2141-2-ND/21755
> 57
>
>
> > Yow! (But two of those on opposite sides of a PCB might make a nice
> isolati=
> > on
> > transformer. :-)
>
> Funnily enough I was going to try that, I have a spectrum analyser
> with tracking generator. Switching frequency is 370 kHz - Anyone care
> to lay bets what the insertion loss will be? :)
>
>
> > This sort of thing really bears measurement. Your original part's
> geometry
> > looks terrifying, but measurement might show it's completely fine.
> Or not.
>
>
> Watch this space...
>
On Wednesday, November 11, 2015 at 11:39:40 AM UTC-5, John Devereux wrote:
> dagmargoodboat@yahoo.com writes:
>
> > On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
> >> On Tue, 10 Nov 2015 09:04:44 -0800 (PST), (dagmargoodboat@yahoo.com)
> >> said:
> >> > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
> >> > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST), (dagmargoo...@yahoo.com)
> >> > > said:
> >> >
> >> [snip]
> >>
> >> > >
> >> > > Thanks for the write-up.
> >> > > The inductor I am using is a different construction again from the two
> >> > > you have mentioned, the windings are on a core which goes parallel to
> >> > > the PCB surface, which is then cemented into a ferrite box. The cross
> >> > > section looks a bit like:
> >> > >
> >> > > +----------------+
> >> > > | |
> >> > > | +------------+ |
> >> > > | | | |
> >> > > | | oooooooooo | |
> >> > > | +------------+ |
> >> > > | |
> >> > > | +------------+ |
> >> > > | | oooooooooo | |
> >> > > | | windings | |
> >> > > | | | |
> >> > > +-+ +-+
> >> > > -------------------------
> >> > > PCB
> >> > > -------------------------
> >> > >
> >> > > So the gap, such as it is, is the (presumably) lower-mu material which
> >> > > joins the core rod to the inside of the box. I'd expect this
> >> > > construction to have a significant downwards fringe field as well, due
> >> > > to the assymmetry.
> >> >
> >> > Man, that's ugly. That's not an inductor, that's a rail gun / field
> >> > projector!
> >> >
> >> > Here's a cross section of the units I used:
> >> > .--..-------..--.
> >> > |.-'|_ _|'-.|
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > |'-..-' '-..-'|
> >> > '--''-------''--'
> >> >
> >> > I guess they can't do this...
> >> > .--..-------..--.
> >> > |.-'|_ _|'-.|
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || .-' '-. ||
> >> > || |_______| ||
> >> > |'-------------'|
> >> > '---------------'
> >> > ....because they need some way to get the leads out the bottom.
> >> >
> >> >
> >> > > Another poster has mentioned the Vishay IHLP series, I will check these
> >> > > out. I'm hoping a different inductor design will help here, having to
> >> > > re-spin this PCB will not make me popular...
> >> >
> >> > If you posted a part number, the intrepid s.e.d. crowd-sourcing crew might
> >> > conjure up a substitute...
> >> >
> >> > Cheers,
> >> > James Arthur
> >> >
> >>
> >> The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
> >> milliohms, in a cubic SMD package roughly 12mm on a side.
> >
> > http://www.digikey.com/product-detail/en/7443320330/732-2141-2-ND/2175557
> >
> > Yow! (But two of those on opposite sides of a PCB might make a nice isolation
> > transformer. :-)
> >
> >> W�rth are normally my go-to supplier of magnetics, I will have to cast
> >> the net a bit wider this time I think.
> >
> > Close, but close enough?
> > http://www.digikey.com/product-detail/en/7443551370/732-1127-1-ND/1639188
> >
> > This sort of thing really bears measurement. Your original part's geometry
> > looks terrifying, but measurement might show it's completely fine. Or
> > not.
>
> Speaking of measurement...
>
> I switched my 4192A to show the series resistance part of the impedance
> and did some more measurements.
>
> SRU1038 22uH, using no-leads (leaded component test fixture).
>
> no plane Groundplane
> f L R L R
>
> 10k 20.41 0.082 20.30 0.091
> 50k 20.30 0.151 19.91 0.231
> 100k 20.19 0.319 19.67 0.439
> 200k 19.99 0.79 19.41 0.930
> 500k 19.52 2.59 18.93 2.73
> 1M 19.10 5.36 18.50 5.56
> 2M 18.90 9.80 18.29 10.10
>
> Not sure what to make of these TBH
The apparent resistance is increased by the following factors:
50K 1.52
100K 1.38
200K 1.17
500K 1.05
I expect those are at least in part real increases in dissipation caused by
stray flux inducing circulating currents in the ground plane.
Both inductor and ground plane e.s.r.s will show skin effect at higher
frequencies. I suspect we're seeing that too, and that the inductor's
added e.s.r. dominates over ground plane losses at higher frequencies (because
the inductor winding path length is sooo much longer than the ground plane's
circulating current's path length).
Cheers,
James
Reply by ●November 11, 20152015-11-11
On Wednesday, November 11, 2015 at 11:37:11 AM UTC-5, John Larkin wrote:
> On Wed, 11 Nov 2015 07:42:29 -0800 (PST), dagmargoodboat@yahoo.com
> wrote:
>
> >On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
> >> On Tue, 10 Nov 2015 09:04:44 -0800 (PST), (dagmargoodboat@yahoo.com)
> >> said:
> >> > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
> >> > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST), (dagmargoo...@yahoo.com)
> >> > > said:
> >> >
> >> [snip]
> >>
> >> > >
> >> > > Thanks for the write-up.
> >> > > The inductor I am using is a different construction again from the two
> >> > > you have mentioned, the windings are on a core which goes parallel to
> >> > > the PCB surface, which is then cemented into a ferrite box. The cross
> >> > > section looks a bit like:
> >> > >
> >> > > +----------------+
> >> > > | |
> >> > > | +------------+ |
> >> > > | | | |
> >> > > | | oooooooooo | |
> >> > > | +------------+ |
> >> > > | |
> >> > > | +------------+ |
> >> > > | | oooooooooo | |
> >> > > | | windings | |
> >> > > | | | |
> >> > > +-+ +-+
> >> > > -------------------------
> >> > > PCB
> >> > > -------------------------
> >> > >
> >> > > So the gap, such as it is, is the (presumably) lower-mu material which
> >> > > joins the core rod to the inside of the box. I'd expect this
> >> > > construction to have a significant downwards fringe field as well, due
> >> > > to the assymmetry.
> >> >
> >> > Man, that's ugly. That's not an inductor, that's a rail gun / field
> >> > projector!
> >> >
> >> > Here's a cross section of the units I used:
> >> > .--..-------..--.
> >> > |.-'|_ _|'-.|
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > |'-..-' '-..-'|
> >> > '--''-------''--'
> >> >
> >> > I guess they can't do this...
> >> > .--..-------..--.
> >> > |.-'|_ _|'-.|
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || oo| |oo ||
> >> > || .-' '-. ||
> >> > || |_______| ||
> >> > |'-------------'|
> >> > '---------------'
> >> > ....because they need some way to get the leads out the bottom.
> >> >
> >> >
> >> > > Another poster has mentioned the Vishay IHLP series, I will check these
> >> > > out. I'm hoping a different inductor design will help here, having to
> >> > > re-spin this PCB will not make me popular...
> >> >
> >> > If you posted a part number, the intrepid s.e.d. crowd-sourcing crew might
> >> > conjure up a substitute...
> >> >
> >> > Cheers,
> >> > James Arthur
> >> >
> >>
> >> The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
> >> milliohms, in a cubic SMD package roughly 12mm on a side.
> >
> >http://www.digikey.com/product-detail/en/7443320330/732-2141-2-ND/2175557
> >
> >Yow! (But two of those on opposite sides of a PCB might make a nice isolation
> >transformer. :-)
> >
> >> W�rth are normally my go-to supplier of magnetics, I will have to cast
> >> the net a bit wider this time I think.
> >
> >Close, but close enough?
> >http://www.digikey.com/product-detail/en/7443551370/732-1127-1-ND/1639188
> >
> >This sort of thing really bears measurement. Your original part's geometry
> >looks terrifying, but measurement might show it's completely fine. Or not.
>
>
> That first (furst?) Wurth part is interesting. They wind the wire on
> some sort of rod, then stick it sideways into the square ferrite box.
> It is sort of shielded.
ISTM the furst is the wurst. Most of the flux goes thru the rod and up
the box thru the top, but potentially a great deal goes down the box walls to
the bottom rim of the box.
^ >>>>>>>> v
^ v
^ oooooo v
+ <<<<<<<< +
v oooooo ^
v ^
v ))))(((( ^
The air gap at the bottom looks like an induction heater, with a low-z shunt
across the top magnetic circuit.
The field is 90 degrees compared to vertically-wound inductors; I'm
still mulling whether that's better for minimizing circulating currents
coupling-wise or not... I think containing the flux in the first place
is more important / matters more.
> At rated current, 17 amps, the L is down about 40%, which means the
> shielding won't be so good there. And the temperature is up 50C!
Cheers,
James Arthur
Reply by RBlack●November 11, 20152015-11-11
On Wed, 11 Nov 2015 07:42:29 -0800 (PST), dagmargoodboat@yahoo.com
wrote:
> On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
> > On Tue, 10 Nov 2015 09:04:44 -0800 (PST),
(dagmargoodboat@yahoo.com)
> > said:
> > > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
> > > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST),
(dagmargoo...@yahoo.com)
> > > > said:
> > >
> > [snip]
> >
> > > >
> > > > Thanks for the write-up.
> > > > The inductor I am using is a different construction again
from the tw=
> o
> > > > you have mentioned, the windings are on a core which goes
parallel to=
> > > > the PCB surface, which is then cemented into a ferrite box.
> h
> > > > joins the core rod to the inside of the box. I'd expect this
> > > > construction to have a significant downwards fringe field as
well, du=
> e
> > > > to the assymmetry.
> > >
> > > Man, that's ugly. That's not an inductor, that's a rail gun /
field
> > > projector!
> > >
> > > Here's a cross section of the units I used:
> > > .--..-------..--.
> > > |.-'|_ _|'-.|
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > |'-..-' '-..-'|
> > > '--''-------''--'
> > >
> > > I guess they can't do this...
> > > .--..-------..--.
> > > |.-'|_ _|'-.|
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || oo| |oo ||
> > > || .-' '-. ||
> > > || |_______| ||
> > > |'-------------'|
> > > '---------------'
> > > ....because they need some way to get the leads out the bottom.
> > >
> > >
> > > > Another poster has mentioned the Vishay IHLP series, I will
check the=
> se
> > > > out. I'm hoping a different inductor design will help here,
having t=
> o
> > > > re-spin this PCB will not make me popular...
> > >
> > > If you posted a part number, the intrepid s.e.d. crowd-sourcing
crew mi=
> ght
> > > conjure up a substitute...
> > >
> > > Cheers,
> > > James Arthur
> > >
> >
> > The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
> > milliohms, in a cubic SMD package roughly 12mm on a side.
> Yow! (But two of those on opposite sides of a PCB might make a nice
isolati=
> on
> transformer. :-)
Funnily enough I was going to try that, I have a spectrum analyser
with tracking generator. Switching frequency is 370 kHz - Anyone care
to lay bets what the insertion loss will be? :)
> > W�rth are normally my go-to supplier of magnetics, I will have to
> This sort of thing really bears measurement. Your original part's
geometry
> looks terrifying, but measurement might show it's completely fine.
Or not.
Watch this space...
Reply by John Devereux●November 11, 20152015-11-11
dagmargoodboat@yahoo.com writes:
> On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
>> On Tue, 10 Nov 2015 09:04:44 -0800 (PST), (dagmargoodboat@yahoo.com)
>> said:
>> > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
>> > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST), (dagmargoo...@yahoo.com)
>> > > said:
>> >
>> [snip]
>>
>> > >
>> > > Thanks for the write-up.
>> > > The inductor I am using is a different construction again from the two
>> > > you have mentioned, the windings are on a core which goes parallel to
>> > > the PCB surface, which is then cemented into a ferrite box. The cross
>> > > section looks a bit like:
>> > >
>> > > +----------------+
>> > > | |
>> > > | +------------+ |
>> > > | | | |
>> > > | | oooooooooo | |
>> > > | +------------+ |
>> > > | |
>> > > | +------------+ |
>> > > | | oooooooooo | |
>> > > | | windings | |
>> > > | | | |
>> > > +-+ +-+
>> > > -------------------------
>> > > PCB
>> > > -------------------------
>> > >
>> > > So the gap, such as it is, is the (presumably) lower-mu material which
>> > > joins the core rod to the inside of the box. I'd expect this
>> > > construction to have a significant downwards fringe field as well, due
>> > > to the assymmetry.
>> >
>> > Man, that's ugly. That's not an inductor, that's a rail gun / field
>> > projector!
>> >
>> > Here's a cross section of the units I used:
>> > .--..-------..--.
>> > |.-'|_ _|'-.|
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > |'-..-' '-..-'|
>> > '--''-------''--'
>> >
>> > I guess they can't do this...
>> > .--..-------..--.
>> > |.-'|_ _|'-.|
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || .-' '-. ||
>> > || |_______| ||
>> > |'-------------'|
>> > '---------------'
>> > ....because they need some way to get the leads out the bottom.
>> >
>> >
>> > > Another poster has mentioned the Vishay IHLP series, I will check these
>> > > out. I'm hoping a different inductor design will help here, having to
>> > > re-spin this PCB will not make me popular...
>> >
>> > If you posted a part number, the intrepid s.e.d. crowd-sourcing crew might
>> > conjure up a substitute...
>> >
>> > Cheers,
>> > James Arthur
>> >
>>
>> The part is Würth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
>> milliohms, in a cubic SMD package roughly 12mm on a side.
>
> http://www.digikey.com/product-detail/en/7443320330/732-2141-2-ND/2175557
>
> Yow! (But two of those on opposite sides of a PCB might make a nice isolation
> transformer. :-)
>
>> Würth are normally my go-to supplier of magnetics, I will have to cast
>> the net a bit wider this time I think.
>
> Close, but close enough?
> http://www.digikey.com/product-detail/en/7443551370/732-1127-1-ND/1639188
>
> This sort of thing really bears measurement. Your original part's geometry
> looks terrifying, but measurement might show it's completely fine. Or
> not.
Speaking of measurement...
I switched my 4192A to show the series resistance part of the impedance
and did some more measurements.
SRU1038 22uH, using no-leads (leaded component test fixture).
no plane Groundplane
f L R L R
10k 20.41 0.082 20.30 0.091
50k 20.30 0.151 19.91 0.231
100k 20.19 0.319 19.67 0.439
200k 19.99 0.79 19.41 0.930
500k 19.52 2.59 18.93 2.73
1M 19.10 5.36 18.50 5.56
2M 18.90 9.80 18.29 10.10
Not sure what to make of these TBH
--
John Devereux
Reply by John Larkin●November 11, 20152015-11-11
On Wed, 11 Nov 2015 07:42:29 -0800 (PST), dagmargoodboat@yahoo.com
wrote:
>On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
>> On Tue, 10 Nov 2015 09:04:44 -0800 (PST), (dagmargoodboat@yahoo.com)
>> said:
>> > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
>> > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST), (dagmargoo...@yahoo.com)
>> > > said:
>> >
>> [snip]
>>
>> > >
>> > > Thanks for the write-up.
>> > > The inductor I am using is a different construction again from the two
>> > > you have mentioned, the windings are on a core which goes parallel to
>> > > the PCB surface, which is then cemented into a ferrite box. The cross
>> > > section looks a bit like:
>> > >
>> > > +----------------+
>> > > | |
>> > > | +------------+ |
>> > > | | | |
>> > > | | oooooooooo | |
>> > > | +------------+ |
>> > > | |
>> > > | +------------+ |
>> > > | | oooooooooo | |
>> > > | | windings | |
>> > > | | | |
>> > > +-+ +-+
>> > > -------------------------
>> > > PCB
>> > > -------------------------
>> > >
>> > > So the gap, such as it is, is the (presumably) lower-mu material which
>> > > joins the core rod to the inside of the box. I'd expect this
>> > > construction to have a significant downwards fringe field as well, due
>> > > to the assymmetry.
>> >
>> > Man, that's ugly. That's not an inductor, that's a rail gun / field
>> > projector!
>> >
>> > Here's a cross section of the units I used:
>> > .--..-------..--.
>> > |.-'|_ _|'-.|
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > |'-..-' '-..-'|
>> > '--''-------''--'
>> >
>> > I guess they can't do this...
>> > .--..-------..--.
>> > |.-'|_ _|'-.|
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || oo| |oo ||
>> > || .-' '-. ||
>> > || |_______| ||
>> > |'-------------'|
>> > '---------------'
>> > ....because they need some way to get the leads out the bottom.
>> >
>> >
>> > > Another poster has mentioned the Vishay IHLP series, I will check these
>> > > out. I'm hoping a different inductor design will help here, having to
>> > > re-spin this PCB will not make me popular...
>> >
>> > If you posted a part number, the intrepid s.e.d. crowd-sourcing crew might
>> > conjure up a substitute...
>> >
>> > Cheers,
>> > James Arthur
>> >
>>
>> The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
>> milliohms, in a cubic SMD package roughly 12mm on a side.
>
>http://www.digikey.com/product-detail/en/7443320330/732-2141-2-ND/2175557
>
>Yow! (But two of those on opposite sides of a PCB might make a nice isolation
>transformer. :-)
>
>> W�rth are normally my go-to supplier of magnetics, I will have to cast
>> the net a bit wider this time I think.
>
>Close, but close enough?
>http://www.digikey.com/product-detail/en/7443551370/732-1127-1-ND/1639188
>
>This sort of thing really bears measurement. Your original part's geometry
>looks terrifying, but measurement might show it's completely fine. Or not.
That first (furst?) Wurth part is interesting. They wind the wire on
some sort of rod, then stick it sideways into the square ferrite box.
It is sort of shielded.
At rated current, 17 amps, the L is down about 40%, which means the
shielding won't be so good there. And the temperature is up 50C!
John
Reply by ●November 11, 20152015-11-11
On Wednesday, November 11, 2015 at 5:27:46 AM UTC-5, RBlack wrote:
> On Tue, 10 Nov 2015 09:04:44 -0800 (PST), (dagmargoodboat@yahoo.com)
> said:
> > On Tuesday, November 10, 2015 at 4:08:48 AM UTC-5, RBlack wrote:
> > > On Fri, 6 Nov 2015 11:19:49 -0800 (PST), (dagmargoo...@yahoo.com)
> > > said:
> >
> [snip]
>
> > >
> > > Thanks for the write-up.
> > > The inductor I am using is a different construction again from the two
> > > you have mentioned, the windings are on a core which goes parallel to
> > > the PCB surface, which is then cemented into a ferrite box. The cross
> > > section looks a bit like:
> > >
> > > +----------------+
> > > | |
> > > | +------------+ |
> > > | | | |
> > > | | oooooooooo | |
> > > | +------------+ |
> > > | |
> > > | +------------+ |
> > > | | oooooooooo | |
> > > | | windings | |
> > > | | | |
> > > +-+ +-+
> > > -------------------------
> > > PCB
> > > -------------------------
> > >
> > > So the gap, such as it is, is the (presumably) lower-mu material which
> > > joins the core rod to the inside of the box. I'd expect this
> > > construction to have a significant downwards fringe field as well, due
> > > to the assymmetry.
> >
> > Man, that's ugly. That's not an inductor, that's a rail gun / field
> > projector!
> >
> > Here's a cross section of the units I used:
> > .--..-------..--.
> > |.-'|_ _|'-.|
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > |'-..-' '-..-'|
> > '--''-------''--'
> >
> > I guess they can't do this...
> > .--..-------..--.
> > |.-'|_ _|'-.|
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > || oo| |oo ||
> > || .-' '-. ||
> > || |_______| ||
> > |'-------------'|
> > '---------------'
> > ....because they need some way to get the leads out the bottom.
> >
> >
> > > Another poster has mentioned the Vishay IHLP series, I will check these
> > > out. I'm hoping a different inductor design will help here, having to
> > > re-spin this PCB will not make me popular...
> >
> > If you posted a part number, the intrepid s.e.d. crowd-sourcing crew might
> > conjure up a substitute...
> >
> > Cheers,
> > James Arthur
> >
>
> The part is W�rth Elektronik 7443320330 - 3.3 uH, 17 amps, 4.4
> milliohms, in a cubic SMD package roughly 12mm on a side.