On Wed, 28 Nov 2012 15:29:24 -0800, Joerg <invalid@invalid.invalid>
wrote:
>legg wrote:
>> On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> legg wrote:
>>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>>> <SaySooth@TheMonastery.org> wrote:
>>>>
>>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>>
>>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>>> <raveninghorde@invalid> wrote:
>>>>>>
>>>>>>> I read many years ago (National app note from memory) that one should
>>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>>> then act as a screen.
>>>>>>>
>>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>>
>>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>>> the inductor is wound?
>>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>>> will only show on the winding sheet.
>>>>>>
>>>>>> You won't get the winding you want without including winding
>>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>>> purchased lot.
>>>>>>
>>>>>> RL
>>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>>> the winding START point. In many cases, it is already part of the
>>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>>> There is no need to mark the winding start of an inductor.
>>>>>
>>>>> An inductor is a non phased device.
>>>>>
>>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>>> has only one winding. ...
>>>
>>> It often does:
>>>
>>> http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>>
>>> [...]
>>
>> and, of course, there was actually a noticeable effect on the EMI
>> plots, when checked........making the effort worthwhile?
>>
>> There'a difference between anecdote and application. There's a
>> difference between a 200W toroid and a shielded bobbin core.
>>
>> The costs of playing it safe, just in case, can whittle a budget past
>> the bare bone.
>>
>
>It already applies at much lower power levels. I finished a flyback
>design a few weeks ago. If you get the winding orientation wrong on
>those then all hell breaks loose at the EMC chambers.
The function of the rf-conductive core body has also to be taken into
account in the radiation process. Capacitance to the core from
different portions of a winding (or windings) has to be taken into
account, as well as possible core body and screen current paths.
>
>The word "shielded" in ferrites is often more a marketing term. A closer
>looks typically reveals a fairly large potting area. The potting
>compound is colored almost the same as the core.
A shielded bobbin core, on the other hand, specifically indicates the
employment of a sleeve structure with a controlled gap, whether SMD or
through-hole. This controlled gap is where the filled adhesive is
present.
RL
Reply by Joerg●November 28, 20122012-11-28
John Larkin wrote:
> On Wed, 28 Nov 2012 15:29:24 -0800, Joerg <invalid@invalid.invalid>
> wrote:
>
>> legg wrote:
>>> On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
>>> wrote:
>>>
>>>> legg wrote:
>>>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>>>> <SaySooth@TheMonastery.org> wrote:
>>>>>
>>>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>>>
>>>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>>>> <raveninghorde@invalid> wrote:
>>>>>>>
>>>>>>>> I read many years ago (National app note from memory) that one should
>>>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>>>> then act as a screen.
>>>>>>>>
>>>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>>>
>>>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>>>> the inductor is wound?
>>>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>>>> will only show on the winding sheet.
>>>>>>>
>>>>>>> You won't get the winding you want without including winding
>>>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>>>> purchased lot.
>>>>>>>
>>>>>>> RL
>>>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>>>> the winding START point. In many cases, it is already part of the
>>>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>>>> There is no need to mark the winding start of an inductor.
>>>>>>
>>>>>> An inductor is a non phased device.
>>>>>>
>>>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>>>> has only one winding. ...
>>>> It often does:
>>>>
>>>> http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>>>
>>>> [...]
>>> and, of course, there was actually a noticeable effect on the EMI
>>> plots, when checked........making the effort worthwhile?
>>>
>>> There'a difference between anecdote and application. There's a
>>> difference between a 200W toroid and a shielded bobbin core.
>>>
>>> The costs of playing it safe, just in case, can whittle a budget past
>>> the bare bone.
>>>
>> It already applies at much lower power levels. I finished a flyback
>> design a few weeks ago. If you get the winding orientation wrong on
>> those then all hell breaks loose at the EMC chambers.
>>
>> The word "shielded" in ferrites is often more a marketing term. A closer
>> looks typically reveals a fairly large potting area. The potting
>> compound is colored almost the same as the core.
>
> Since some ferrites are conductive, it's not always obvious which
> connection will radiate less.
>
True, but fairly easy to test when you have a near field probe kit. That
kit is probably the most worn tool out here. Other than the bottle
opener :-)
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by John Larkin●November 28, 20122012-11-28
On Wed, 28 Nov 2012 15:29:24 -0800, Joerg <invalid@invalid.invalid>
wrote:
>legg wrote:
>> On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> legg wrote:
>>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>>> <SaySooth@TheMonastery.org> wrote:
>>>>
>>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>>
>>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>>> <raveninghorde@invalid> wrote:
>>>>>>
>>>>>>> I read many years ago (National app note from memory) that one should
>>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>>> then act as a screen.
>>>>>>>
>>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>>
>>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>>> the inductor is wound?
>>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>>> will only show on the winding sheet.
>>>>>>
>>>>>> You won't get the winding you want without including winding
>>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>>> purchased lot.
>>>>>>
>>>>>> RL
>>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>>> the winding START point. In many cases, it is already part of the
>>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>>> There is no need to mark the winding start of an inductor.
>>>>>
>>>>> An inductor is a non phased device.
>>>>>
>>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>>> has only one winding. ...
>>>
>>> It often does:
>>>
>>> http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>>
>>> [...]
>>
>> and, of course, there was actually a noticeable effect on the EMI
>> plots, when checked........making the effort worthwhile?
>>
>> There'a difference between anecdote and application. There's a
>> difference between a 200W toroid and a shielded bobbin core.
>>
>> The costs of playing it safe, just in case, can whittle a budget past
>> the bare bone.
>>
>
>It already applies at much lower power levels. I finished a flyback
>design a few weeks ago. If you get the winding orientation wrong on
>those then all hell breaks loose at the EMC chambers.
>
>The word "shielded" in ferrites is often more a marketing term. A closer
>looks typically reveals a fairly large potting area. The potting
>compound is colored almost the same as the core.
Since some ferrites are conductive, it's not always obvious which
connection will radiate less.
--
John Larkin Highland Technology, Inc
jlarkin at highlandtechnology dot com
http://www.highlandtechnology.com
Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom laser drivers and controllers
Photonics and fiberoptic TTL data links
VME thermocouple, LVDT, synchro acquisition and simulation
Reply by Joerg●November 28, 20122012-11-28
legg wrote:
> On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
> wrote:
>
>> legg wrote:
>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>> <SaySooth@TheMonastery.org> wrote:
>>>
>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>
>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>> <raveninghorde@invalid> wrote:
>>>>>
>>>>>> I read many years ago (National app note from memory) that one should
>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>> then act as a screen.
>>>>>>
>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>
>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>> the inductor is wound?
>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>> will only show on the winding sheet.
>>>>>
>>>>> You won't get the winding you want without including winding
>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>> purchased lot.
>>>>>
>>>>> RL
>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>> the winding START point. In many cases, it is already part of the
>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>> There is no need to mark the winding start of an inductor.
>>>>
>>>> An inductor is a non phased device.
>>>>
>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>> has only one winding. ...
>>
>> It often does:
>>
>> http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>
>> [...]
>
> and, of course, there was actually a noticeable effect on the EMI
> plots, when checked........making the effort worthwhile?
>
> There'a difference between anecdote and application. There's a
> difference between a 200W toroid and a shielded bobbin core.
>
> The costs of playing it safe, just in case, can whittle a budget past
> the bare bone.
>
It already applies at much lower power levels. I finished a flyback
design a few weeks ago. If you get the winding orientation wrong on
those then all hell breaks loose at the EMC chambers.
The word "shielded" in ferrites is often more a marketing term. A closer
looks typically reveals a fairly large potting area. The potting
compound is colored almost the same as the core.
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by legg●November 28, 20122012-11-28
On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
wrote:
>legg wrote:
>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>> <SaySooth@TheMonastery.org> wrote:
>>
>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>
>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>> <raveninghorde@invalid> wrote:
>>>>
>>>>> I read many years ago (National app note from memory) that one should
>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>> then act as a screen.
>>>>>
>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>
>>>>> With many modern inductors it is impossible to see how they are wound
>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>> the inductor is wound?
>>>> It indicates phasing alone. Constructional details, where critical,
>>>> will only show on the winding sheet.
>>>>
>>>> You won't get the winding you want without including winding
>>>> instructions in the transformer drawing and then batch inspecting each
>>>> purchased lot.
>>>>
>>>> RL
>>>
>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>> the winding START point. In many cases, it is already part of the
>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>> There is no need to mark the winding start of an inductor.
>>>
>>> An inductor is a non phased device.
>>>
>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>
>> It is highly unlikely that a dot will occur on a magnetic drawing that
>> has only one winding. ...
>
>
>It often does:
>
>http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>
>[...]
and, of course, there was actually a noticeable effect on the EMI
plots, when checked........making the effort worthwhile?
There'a difference between anecdote and application. There's a
difference between a 200W toroid and a shielded bobbin core.
The costs of playing it safe, just in case, can whittle a budget past
the bare bone.
RL
Reply by Joerg●November 28, 20122012-11-28
legg wrote:
> On Wed, 28 Nov 2012 09:56:15 +0000, Raveninghorde
> <raveninghorde@invalid> wrote:
>
>> On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> legg wrote:
>>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>>> <SaySooth@TheMonastery.org> wrote:
>>>>
>>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>>
>>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>>> <raveninghorde@invalid> wrote:
>>>>>>
>>>>>>> I read many years ago (National app note from memory) that one should
>>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>>> then act as a screen.
>>>>>>>
>>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>>
>>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>>> the inductor is wound?
>>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>>> will only show on the winding sheet.
>>>>>>
>>>>>> You won't get the winding you want without including winding
>>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>>> purchased lot.
>>>>>>
>>>>>> RL
>>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>>> the winding START point. In many cases, it is already part of the
>>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>>> There is no need to mark the winding start of an inductor.
>>>>>
>>>>> An inductor is a non phased device.
>>>>>
>>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>>> has only one winding. ...
>>>
>>> It often does:
>>>
>>> http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>>
>>> [...]
>> Or
>>
>> http://www.coilcraft.com/pdf_viewer/showpdf.cfm?f=pdf_store:lps5015.pdf
>
> Interesting; both of them. At a quick glance, they are unique in the
> range of both manufacturers.
>
> For Coilcraft, the 'dot' isn't actually associared with either solder
> junction, but appears equidistant between the two......so you'd have
> to crack one open to figure out what they mean, and hope that the
> meaning isn't subverted in the part's sales lifetime. It's not
> guaranteed that the coil winding personnel have even a working
> familiarity with the language of the spec......
>
> The instruction 'winding direction' is unfortunately ambiguous in the
> English language, as winding is both a noun and a verb. When
> indicating prefered wire layout, I always indicate the direction of
> the coil former's rotation (ie the verb sense of the winding machine's
> function) and illustrate the movement of the physical part, to avoid
> this (hopefully....).
>
On Wed, 28 Nov 2012 09:56:15 +0000, Raveninghorde
<raveninghorde@invalid> wrote:
>On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
>wrote:
>
>>legg wrote:
>>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>>> <SaySooth@TheMonastery.org> wrote:
>>>
>>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>>
>>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>>> <raveninghorde@invalid> wrote:
>>>>>
>>>>>> I read many years ago (National app note from memory) that one should
>>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>>> then act as a screen.
>>>>>>
>>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>>
>>>>>> With many modern inductors it is impossible to see how they are wound
>>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>>> the inductor is wound?
>>>>> It indicates phasing alone. Constructional details, where critical,
>>>>> will only show on the winding sheet.
>>>>>
>>>>> You won't get the winding you want without including winding
>>>>> instructions in the transformer drawing and then batch inspecting each
>>>>> purchased lot.
>>>>>
>>>>> RL
>>>>
>>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>>> the winding START point. In many cases, it is already part of the
>>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>>> There is no need to mark the winding start of an inductor.
>>>>
>>>> An inductor is a non phased device.
>>>>
>>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>>
>>> It is highly unlikely that a dot will occur on a magnetic drawing that
>>> has only one winding. ...
>>
>>
>>It often does:
>>
>>http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>>
>>[...]
>
>Or
>
>http://www.coilcraft.com/pdf_viewer/showpdf.cfm?f=pdf_store:lps5015.pdf
Interesting; both of them. At a quick glance, they are unique in the
range of both manufacturers.
For Coilcraft, the 'dot' isn't actually associared with either solder
junction, but appears equidistant between the two......so you'd have
to crack one open to figure out what they mean, and hope that the
meaning isn't subverted in the part's sales lifetime. It's not
guaranteed that the coil winding personnel have even a working
familiarity with the language of the spec......
The instruction 'winding direction' is unfortunately ambiguous in the
English language, as winding is both a noun and a verb. When
indicating prefered wire layout, I always indicate the direction of
the coil former's rotation (ie the verb sense of the winding machine's
function) and illustrate the movement of the physical part, to avoid
this (hopefully....).
RL
Reply by Joerg●November 28, 20122012-11-28
Raveninghorde wrote:
> On Tue, 27 Nov 2012 10:43:12 -0800, Joerg <invalid@invalid.invalid>
> wrote:
>
>> Raveninghorde wrote:
>>> On Mon, 26 Nov 2012 17:27:46 -0800, Joerg <invalid@invalid.invalid>
>>> wrote:
>>>
>>>> Raveninghorde wrote:
>>>>> I read many years ago (National app note from memory) that one should
>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>> then act as a screen.
>>>>>
>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>
>>>>> With many modern inductors it is impossible to see how they are wound
>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>> the inductor is wound?
>>>> Nope, no standard there. Fastest way to find out is crack one open and
>>>> look. Watch out for ferrite shrapnel. The gentle method is to measure
>>>> the RF leaking out with one end grounded and the other energized, then
>>>> reverse. Then talk to the mfg whether their production procedure (SOP)
>>>> calls out to always connect in this particular way. Typically they are
>>>> but it can be tough to obtain something in writing about it.
>>> I've just checked with a German manufacturer and they confirm the dot
>>> on their inductors is the start of the inner winding.
>>>
>>> I appreciate not all manufacturers will necessarily be as consistent.
>>
>> Great, then at least you found one where they have a system to it. If
>> this is for a product design I'd still get that in writing though.
>
> What they said by email was:
>
> The dot signifies the start of the winding on the inductor, thus this
> would be the inner layer of the windings which would connect to the
> hot side of the output of the DC/DC converter. The outer winding of
> the inductor in effect self shields the emi on the inner windings.
Perfect, then you got it in writing. I thought it was just a phone
conversation across the Channel.
--
Regards, Joerg
http://www.analogconsultants.com/
Reply by Raveninghorde●November 28, 20122012-11-28
On Tue, 27 Nov 2012 10:43:12 -0800, Joerg <invalid@invalid.invalid>
wrote:
>Raveninghorde wrote:
>> On Mon, 26 Nov 2012 17:27:46 -0800, Joerg <invalid@invalid.invalid>
>> wrote:
>>
>>> Raveninghorde wrote:
>>>> I read many years ago (National app note from memory) that one should
>>>> connect the inner layer of an inductor to the switch in a buck
>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>> then act as a screen.
>>>>
>>>> I don't know if it makes a difference in practice but it's free.
>>>>
>>>> With many modern inductors it is impossible to see how they are wound
>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>> and down to the winder or does it actually relate in anyway to the way
>>>> the inductor is wound?
>>>
>>> Nope, no standard there. Fastest way to find out is crack one open and
>>> look. Watch out for ferrite shrapnel. The gentle method is to measure
>>> the RF leaking out with one end grounded and the other energized, then
>>> reverse. Then talk to the mfg whether their production procedure (SOP)
>>> calls out to always connect in this particular way. Typically they are
>>> but it can be tough to obtain something in writing about it.
>>
>> I've just checked with a German manufacturer and they confirm the dot
>> on their inductors is the start of the inner winding.
>>
>> I appreciate not all manufacturers will necessarily be as consistent.
>
>
>Great, then at least you found one where they have a system to it. If
>this is for a product design I'd still get that in writing though.
What they said by email was:
The dot signifies the start of the winding on the inductor, thus this
would be the inner layer of the windings which would connect to the
hot side of the output of the DC/DC converter. The outer winding of
the inductor in effect self shields the emi on the inner windings.
Reply by Raveninghorde●November 28, 20122012-11-28
On Tue, 27 Nov 2012 14:06:35 -0800, Joerg <invalid@invalid.invalid>
wrote:
>legg wrote:
>> On Mon, 26 Nov 2012 15:44:04 -0800, SoothSayer
>> <SaySooth@TheMonastery.org> wrote:
>>
>>> On Mon, 26 Nov 2012 16:40:18 -0500, legg <legg@nospam.magma.ca> wrote:
>>>
>>>> On Mon, 26 Nov 2012 16:48:51 +0000, Raveninghorde
>>>> <raveninghorde@invalid> wrote:
>>>>
>>>>> I read many years ago (National app note from memory) that one should
>>>>> connect the inner layer of an inductor to the switch in a buck
>>>>> regulator and the outer layer to the capacitor as the outer layer will
>>>>> then act as a screen.
>>>>>
>>>>> I don't know if it makes a difference in practice but it's free.
>>>>>
>>>>> With many modern inductors it is impossible to see how they are wound
>>>>> so the only indication of "polarity" is the dot. Is the dot arbitary
>>>>> and down to the winder or does it actually relate in anyway to the way
>>>>> the inductor is wound?
>>>> It indicates phasing alone. Constructional details, where critical,
>>>> will only show on the winding sheet.
>>>>
>>>> You won't get the winding you want without including winding
>>>> instructions in the transformer drawing and then batch inspecting each
>>>> purchased lot.
>>>>
>>>> RL
>>>
>>> The dot is for phasing of a TRANSFORMER. In such a case, it indicates
>>> the winding START point. In many cases, it is already part of the
>>> bobbin. In some cases, it gets painted on as part of the winding process.
>>> There is no need to mark the winding start of an inductor.
>>>
>>> An inductor is a non phased device.
>>>
>>> No, it matters not which 'way' it gets utilized. AT ALL.
>>
>> It is highly unlikely that a dot will occur on a magnetic drawing that
>> has only one winding. ...
>
>
>It often does:
>
>http://katalog.we-online.de/kataloge/eisos/media/pdf/744778920.pdf
>
>[...]