On Thu, 19 Jan 2012 07:53:49 -0600, amdx <amdx@knologynotthis.net> wrote:
>On 1/18/2012 10:07 PM, josephkk wrote:
>> On Wed, 18 Jan 2012 06:40:57 -0600, amdx<amdx@knologynotthis.net> =
wrote:
>>
>>> On 1/17/2012 9:38 PM, josephkk wrote:
>>>> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> =
wrote:
>>>>
>>>>>
>>>>>> Remember, the Tonghui measured .52H even on the 1kHz setting. =
That's
>>>>>> plenty good for me.
>>>>>>
>>>>>> What this tells me is that I cannot trust *any* RLC meter to give =
me the
>>>>>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>>>>>
>>>>>> I have a lot more to learn about magnetics. But, the Tonghui is =
not at
>>>>>> fault and I need more education.
>>>>>>
>>>>>> Cheers,
>>>>>> John S
>>>>>
>>>>> It's all in the "Slope of the BH curve".
>>>>> At low currents the slope of the BH curve is more vertical and =
turns
>>>>> horizontal at higher current.
>>>>> See the link,
>>>>>
>>>>> =
>>>>>
>>>>> Click it, it opens to a pdf, then it is large enough to see the =
slope of
>>>>> the initial ramp up, ( the line that starts at 0,0) which is what I
>>>>> think is similar to the slope at the low currents.
>>>>> Mikek
>>>>>
>>>>
>>>> In the hysteresis curves please not that there is a small low slope =
part
>>>> just coming off 0,0. That is part of where it is coming from.
>>>>
>>>> ?-)
>>> Sorry, can you rephrase that, I don't understand what you wanted to =
say.
>>> Mikek
>>
>> Tim Williams explained it soo much better. At very low flux levels =
there
>> is a lower proportion of domains responding (per Ampere Turn) to the
>> impressed flux, thus lower effective Mu(r) and lower inductance.
>>
>> ?-)
>
> That's very good. I have ask a couple of times about this phenomena=20
>and could not generate any interest.
> My line of questioning had to do with transformers at the RF input of=
=20
>a radio. The signal can be as low as 1 uV.(less than a picowatt) I'm=20
>sure when you look at the spec's for *Mu(r) it was measured at much=20
>higher power levels. So the transformers used at these low levels should=
=20
>have many more turns than the spec's would lead you to believe.
> Yet, I have not seen any references to support this.
Not that i claim to really understand this (let alone well), i am pretty
sure that much of this is a material dependant property. Laminated core
power transformers would be rather bad about this (they normally would
have plenty of magnetizing current). And ferrite RF materials would be
very nearly independent of this. But that is just a guess.
>
>*Mu(r) I'm assuming this symbol is for initial permeability, I have
>not seen it put this way.
Relative permeability, (Mu of the material/Mu of space).
> Ok, I Googled Mu and got ?.
>Ya, I had to copy and paste the symbol.
> Thanks, Mikek
>
Reply by josephkk●January 21, 20122012-01-21
On Thu, 19 Jan 2012 08:36:04 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
>josephkk wrote:
>>=20
>> On Wed, 18 Jan 2012 06:40:57 -0600, amdx <amdx@knologynotthis.net> =
wrote:
>>=20
>> >On 1/17/2012 9:38 PM, josephkk wrote:
>> >> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> =
wrote:
>> >>
>> >>>
>> >>>> Remember, the Tonghui measured .52H even on the 1kHz setting. =
That's
>> >>>> plenty good for me.
>> >>>>
>> >>>> What this tells me is that I cannot trust *any* RLC meter to give=
me the
>> >>>> inductance of a 60Hz piece of magnetics at low excitation =
voltage.
>> >>>>
>> >>>> I have a lot more to learn about magnetics. But, the Tonghui is =
not at
>> >>>> fault and I need more education.
>> >>>>
>> >>>> Cheers,
>> >>>> John S
>> >>>
>> >>> It's all in the "Slope of the BH curve".
>> >>> At low currents the slope of the BH curve is more vertical and =
turns
>> >>> horizontal at higher current.
>> >>> See the link,
>> >>>
>> >>> =
>> >>>
>> >>> Click it, it opens to a pdf, then it is large enough to see the =
slope of
>> >>> the initial ramp up, ( the line that starts at 0,0) which is what =
I
>> >>> think is similar to the slope at the low currents.
>> >>> Mikek
>> >>>
>> >>
>> >> In the hysteresis curves please not that there is a small low slope=
part
>> >> just coming off 0,0. That is part of where it is coming from.
>> >>
>> >> ?-)
>> >Sorry, can you rephrase that, I don't understand what you wanted to =
say.
>> > Mikek
>>=20
>> Tim Williams explained it soo much better. At very low flux levels =
there
>> is a lower proportion of domains responding (per Ampere Turn) to the
>> impressed flux, thus lower effective Mu(r) and lower inductance.
>>=20
>> ?-)
>
>Sort of like a magnetic version of crossover distortion.
Thanks for the new (to me) analogy.
>
>Cheers
>
>Phil Hobbs
Reply by John S●January 20, 20122012-01-20
On 1/17/2012 9:55 PM, Tim Williams wrote:
> "josephkk"<joseph_barrett@sbcglobal.net> wrote in message
> news:ruech7leag4uj6kv30qqs99r3a4tk7tub2@4ax.com...
>>> <low level inductance>
>>
>> Maybe someone here who does know something about magnetics can help us
>> out here.
>
> Quite simply, magnetic domains are "sticky". Down at low levels, buried
> in the hysteresis loop of the material, small-signal loops are flatter
> because few domains are responding.
>
> I'm sure this effect has a strong tempco, since higher temperatures free
> more domains (much like dithering a balance to get it to the equilibrium
> position despite bearing friction). It's present in all metallic
> materials I know of, though you'll have a hard time measuring it in
> super-high permeability materials due to the extremely small hysteresis
> loop, and in powdered materials, since they have a lot of gap in the
> matrix already.
>
> Still, powdered materials yield a fair amount of change:
> http://www.micrometals.com/materials_index.html
> Mix 26 is the familiar yellow/white toroid used in just about every power
> supply, quite cheap and lossy, but high permeability (mu = 75).
>
> I'm trying to remember if I've seen an analogous curve for ferrites. If I
> have, I don't remember which manufacturer had the curve...
>
> The tempco is more easily observed in ferrites than metals, since the
> curie temperature is lower (which is like a magnetic "melting point"; it
> loses all order and ceases to be ferro/ferrimagnetic at that temperature).
> Permeability almost always rises on approaching the curie point (which, I
> suppose, is like water becoming less viscous as it approaches the boiling
> point), which means more domains are being more easily moved; meanwhile,
> saturation flux goes down, which means fewer and fewer are staying in
> their polarized positions. At curie, Bsat suddenly drops to air-cored
> levels.
>
>>> This is a very important subject for the Tonghui. If you want to gap
>>> a core, you need to know the inductance you should get after gapping
>>> to confirm it is correct. If the Tonghui can't measure it, I think
>>> we're in trouble.
>
> Well, a gapped core doesn't depend on the core very much, so you're okay
> on that one. I'd worry more about the expansion tempco of whatever the
> core spacing material is!
>
> Tim
>
Your explanation makes a lot of sense, Tim. Thanks very much.
John S
Reply by amdx●January 19, 20122012-01-19
On 1/18/2012 10:07 PM, josephkk wrote:
> On Wed, 18 Jan 2012 06:40:57 -0600, amdx<amdx@knologynotthis.net> wrote:
>
>> On 1/17/2012 9:38 PM, josephkk wrote:
>>> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> wrote:
>>>
>>>>
>>>>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>>>>> plenty good for me.
>>>>>
>>>>> What this tells me is that I cannot trust *any* RLC meter to give me the
>>>>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>>>>
>>>>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>>>>> fault and I need more education.
>>>>>
>>>>> Cheers,
>>>>> John S
>>>>
>>>> It's all in the "Slope of the BH curve".
>>>> At low currents the slope of the BH curve is more vertical and turns
>>>> horizontal at higher current.
>>>> See the link,
>>>>
>>>> http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>>>>
>>>> Click it, it opens to a pdf, then it is large enough to see the slope of
>>>> the initial ramp up, ( the line that starts at 0,0) which is what I
>>>> think is similar to the slope at the low currents.
>>>> Mikek
>>>>
>>>
>>> In the hysteresis curves please not that there is a small low slope part
>>> just coming off 0,0. That is part of where it is coming from.
>>>
>>> ?-)
>> Sorry, can you rephrase that, I don't understand what you wanted to say.
>> Mikek
>
> Tim Williams explained it soo much better. At very low flux levels there
> is a lower proportion of domains responding (per Ampere Turn) to the
> impressed flux, thus lower effective Mu(r) and lower inductance.
>
> ?-)
That's very good. I have ask a couple of times about this phenomena
and could not generate any interest.
My line of questioning had to do with transformers at the RF input of
a radio. The signal can be as low as 1 uV.(less than a picowatt) I'm
sure when you look at the spec's for *Mu(r) it was measured at much
higher power levels. So the transformers used at these low levels should
have many more turns than the spec's would lead you to believe.
Yet, I have not seen any references to support this.
*Mu(r) I'm assuming this symbol is for initial permeability, I have
not seen it put this way.
Ok, I Googled Mu and got μ.
Ya, I had to copy and paste the symbol.
Thanks, Mikek
Reply by Phil Hobbs●January 19, 20122012-01-19
josephkk wrote:
>
> On Wed, 18 Jan 2012 06:40:57 -0600, amdx <amdx@knologynotthis.net> wrote:
>
> >On 1/17/2012 9:38 PM, josephkk wrote:
> >> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> wrote:
> >>
> >>>
> >>>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
> >>>> plenty good for me.
> >>>>
> >>>> What this tells me is that I cannot trust *any* RLC meter to give me the
> >>>> inductance of a 60Hz piece of magnetics at low excitation voltage.
> >>>>
> >>>> I have a lot more to learn about magnetics. But, the Tonghui is not at
> >>>> fault and I need more education.
> >>>>
> >>>> Cheers,
> >>>> John S
> >>>
> >>> It's all in the "Slope of the BH curve".
> >>> At low currents the slope of the BH curve is more vertical and turns
> >>> horizontal at higher current.
> >>> See the link,
> >>>
> >>> http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
> >>>
> >>> Click it, it opens to a pdf, then it is large enough to see the slope of
> >>> the initial ramp up, ( the line that starts at 0,0) which is what I
> >>> think is similar to the slope at the low currents.
> >>> Mikek
> >>>
> >>
> >> In the hysteresis curves please not that there is a small low slope part
> >> just coming off 0,0. That is part of where it is coming from.
> >>
> >> ?-)
> >Sorry, can you rephrase that, I don't understand what you wanted to say.
> > Mikek
>
> Tim Williams explained it soo much better. At very low flux levels there
> is a lower proportion of domains responding (per Ampere Turn) to the
> impressed flux, thus lower effective Mu(r) and lower inductance.
>
> ?-)
Sort of like a magnetic version of crossover distortion.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058
hobbs at electrooptical dot net
http://electrooptical.net
Reply by josephkk●January 19, 20122012-01-19
On Wed, 18 Jan 2012 06:40:57 -0600, amdx <amdx@knologynotthis.net> wrote:
>On 1/17/2012 9:38 PM, josephkk wrote:
>> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> =
wrote:
>>
>>>
>>>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>>>> plenty good for me.
>>>>
>>>> What this tells me is that I cannot trust *any* RLC meter to give me=
the
>>>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>>>
>>>> I have a lot more to learn about magnetics. But, the Tonghui is not =
at
>>>> fault and I need more education.
>>>>
>>>> Cheers,
>>>> John S
>>>
>>> It's all in the "Slope of the BH curve".
>>> At low currents the slope of the BH curve is more vertical and turns
>>> horizontal at higher current.
>>> See the link,
>>>
>>> =
>>>
>>> Click it, it opens to a pdf, then it is large enough to see the slope=
of
>>> the initial ramp up, ( the line that starts at 0,0) which is what I
>>> think is similar to the slope at the low currents.
>>> Mikek
>>>
>>
>> In the hysteresis curves please not that there is a small low slope =
part
>> just coming off 0,0. That is part of where it is coming from.
>>
>> ?-)
>Sorry, can you rephrase that, I don't understand what you wanted to say.
> Mikek
Tim Williams explained it soo much better. At very low flux levels there
is a lower proportion of domains responding (per Ampere Turn) to the
impressed flux, thus lower effective Mu(r) and lower inductance.
?-)
Reply by John S●January 18, 20122012-01-18
On 1/17/2012 5:50 PM, amdx wrote:
> On 1/17/2012 3:27 PM, John S wrote:
>> On 1/16/2012 4:16 PM, Mike wrote:
>>> John S<Sophi.2@invalid.org> wrote:
>>
>>> > It appears that the proper frequency range is called for to begin
>>> > with. Not a big surprise, I guess, considering how hard it must be
>>> > to measure 300pF at 100Hz. Not bad, huh?
>>>
>>> Actually that's pretty good.
>>
>>
>> Indeed! No complaints from this end.
>>
>>
>>> [...]
>>>
>>> > No. If I measure the primary inductance on the Tonghui (at 100Hz),
>>> > I get about 535mH and Q of 10. That would calculate out to about
>>> > 600ma of unloaded (magnetizing) current at 124VAC, 60 Hz. If I
>>> > then apply 124AC at 60Hz to the primary and measure the current, I
>>> > get 0.078mA.
>>>
>>> > This calculates out to about 4H. I'd like to learn why there is so
>>> > much discrepancy.
>>
>> I've done a couple of investigations since yesterday to try to get to
>> the bottom of this.
>>
>> First, I checked my Tonghui data against an old HP4260A Universal
>> Bridge, bought on eek-Bay and long out of calibration. I can produce the
>> data if you wish, but the crux of it is that they agree with each other.
>>
>> Well, I tell myself, the transformer must be producing unexpected data.
>>
>> First, I checked the Tonghui for output voltage when the transformer was
>> attached. The lower frequency settings (exclude the 10kHz setting)
>> produced 98 to 141mV RMS.
>>
>> I then connected the transformer to an HP audio oscillator set for 60Hz
>> and an HP3400A RMS meter. The results were not only surprising to me,
>> but they were good support for the believability of the data produced by
>> the Tonghui.
>>
>> E(source) V(L) XL(calc) L(calc)
>> 5 3 450 1.2H
>> 3 1.5 350 .92H
>> .1 .038 247 .66H
>>
>> Wow! The inductance goes down as the excitation voltage decreases?
>>
>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>> plenty good for me.
>>
>> What this tells me is that I cannot trust *any* RLC meter to give me the
>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>
>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>> fault and I need more education.
>>
>> Cheers,
>> John S
>
> It's all in the "Slope of the BH curve".
> At low currents the slope of the BH curve is more vertical and turns
> horizontal at higher current.
> See the link,
>
> http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>
> Click it, it opens to a pdf, then it is large enough to see the slope of
> the initial ramp up, ( the line that starts at 0,0) which is what I
> think is similar to the slope at the low currents.
> Mikek
Thanks for the links, Mikek, and for your comments, josephkk.
I spent all morning researching the question. The best answer I could
find was here:
http://www.magmet.com/lamination/pdf/Superperm49.pdf
Note that the AC permeability (page 1) increases with increasing flux
density. A crude estimate of the B involved with my measurements gives
about 60 gauss (.1V @ 100Hz) for the Tonghui and about 600 gauss when
the HP audio oscillator was set for 5V.
The AC permeability would therefore go from about 6000 to about 30,000
for about a 5 to 1 increase in inductance. My actual measurements were
about 2 to 1, but, as I said, this is a very crude estimate.
This doesn't answer *why* the permeability changes, but does point out
that the inductance of cored inductors will change with B. So, I think
we can expect usually lower inductance readings from the Tonghui,
especially for the power magnetics cases.
Here is another shot showing powdered iron core changes of inductance
with flux density:
http://www.micrometals.com/material/AC60HzDsgntxt.html
Cheers,
John S
Reply by amdx●January 18, 20122012-01-18
On 1/17/2012 9:38 PM, josephkk wrote:
> On Tue, 17 Jan 2012 17:50:47 -0600, amdx<amdx@knologynotthis.net> wrote:
>
>>
>>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>>> plenty good for me.
>>>
>>> What this tells me is that I cannot trust *any* RLC meter to give me the
>>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>>
>>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>>> fault and I need more education.
>>>
>>> Cheers,
>>> John S
>>
>> It's all in the "Slope of the BH curve".
>> At low currents the slope of the BH curve is more vertical and turns
>> horizontal at higher current.
>> See the link,
>>
>> http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>>
>> Click it, it opens to a pdf, then it is large enough to see the slope of
>> the initial ramp up, ( the line that starts at 0,0) which is what I
>> think is similar to the slope at the low currents.
>> Mikek
>>
>
> In the hysteresis curves please not that there is a small low slope part
> just coming off 0,0. That is part of where it is coming from.
>
> ?-)
Sorry, can you rephrase that, I don't understand what you wanted to say.
Mikek
Reply by Tim Williams●January 17, 20122012-01-17
"josephkk" <joseph_barrett@sbcglobal.net> wrote in message
news:ruech7leag4uj6kv30qqs99r3a4tk7tub2@4ax.com...
> > <low level inductance>
>
> Maybe someone here who does know something about magnetics can help us
> out here.
Quite simply, magnetic domains are "sticky". Down at low levels, buried
in the hysteresis loop of the material, small-signal loops are flatter
because few domains are responding.
I'm sure this effect has a strong tempco, since higher temperatures free
more domains (much like dithering a balance to get it to the equilibrium
position despite bearing friction). It's present in all metallic
materials I know of, though you'll have a hard time measuring it in
super-high permeability materials due to the extremely small hysteresis
loop, and in powdered materials, since they have a lot of gap in the
matrix already.
Still, powdered materials yield a fair amount of change:
http://www.micrometals.com/materials_index.html
Mix 26 is the familiar yellow/white toroid used in just about every power
supply, quite cheap and lossy, but high permeability (mu = 75).
I'm trying to remember if I've seen an analogous curve for ferrites. If I
have, I don't remember which manufacturer had the curve...
The tempco is more easily observed in ferrites than metals, since the
curie temperature is lower (which is like a magnetic "melting point"; it
loses all order and ceases to be ferro/ferrimagnetic at that temperature).
Permeability almost always rises on approaching the curie point (which, I
suppose, is like water becoming less viscous as it approaches the boiling
point), which means more domains are being more easily moved; meanwhile,
saturation flux goes down, which means fewer and fewer are staying in
their polarized positions. At curie, Bsat suddenly drops to air-cored
levels.
> > This is a very important subject for the Tonghui. If you want to gap
> > a core, you need to know the inductance you should get after gapping
> > to confirm it is correct. If the Tonghui can't measure it, I think
> > we're in trouble.
Well, a gapped core doesn't depend on the core very much, so you're okay
on that one. I'd worry more about the expansion tempco of whatever the
core spacing material is!
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Reply by josephkk●January 17, 20122012-01-17
On Tue, 17 Jan 2012 17:50:47 -0600, amdx <amdx@knologynotthis.net> wrote:
>
>> Remember, the Tonghui measured .52H even on the 1kHz setting. That's
>> plenty good for me.
>>
>> What this tells me is that I cannot trust *any* RLC meter to give me =
the
>> inductance of a 60Hz piece of magnetics at low excitation voltage.
>>
>> I have a lot more to learn about magnetics. But, the Tonghui is not at
>> fault and I need more education.
>>
>> Cheers,
>> John S
>
> It's all in the "Slope of the BH curve".
>At low currents the slope of the BH curve is more vertical and turns=20
>horizontal at higher current.
> See the link,
>
>http://www.arnoldmagnetics.com/Non_Grain_Oriented_Electrical_Steel.aspx
>
>Click it, it opens to a pdf, then it is large enough to see the slope of=
=20
>the initial ramp up, ( the line that starts at 0,0) which is what I=20
>think is similar to the slope at the low currents.
> Mikek
>
In the hysteresis curves please not that there is a small low slope part
just coming off 0,0. That is part of where it is coming from.
?-)