Author Topic: "over current" use of a Pulse transformer - ( or an alternative )  (Read 7693 times)

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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #25 on: December 25, 2018, 07:22:38 pm »
One would hope, the transformer is designed with nominal imbalance in mind.  This does however limit the average permeability, which means more core size and wire length are more limited (larger).

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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #26 on: December 25, 2018, 09:25:41 pm »
Yes, one would hope so.   

I've contacted TDK and hope they will come back with some more info.   
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #27 on: December 25, 2018, 09:47:03 pm »
One would hope, the transformer is designed with nominal imbalance in mind.

Yes they indeed are designed exactly that way. That's why you never shall exceed current specs of transformer and whole discussion about "over current" use of a Pulse transformer ends with such conclusion.

Ogden, we'll see what happens.  You nor i actually know the characterisistics of this transformer for operating outside the rated limits. ( i assume you hav'nt tested it, in this situation, but if you have, i'd be all ears ).   For me, its well worth pursuing this. If it works i'll be very happy. If it does'tn i've not lost a lot.
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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #28 on: December 25, 2018, 11:27:04 pm »
Nice thing is because it's intended to be a bias tee, you can intentionally unbalance it in a test, run some current through it, and measure the saturation flux on the free winding(s)!

Just gotta order up some parts and put 'em to the function generator and scope.

Tim
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #29 on: December 26, 2018, 04:13:47 am »
Ogden, we'll see what happens.  You nor i actually know the characterisistics of this transformer for operating outside the rated limits.

Your assumptions about what others know may fail miserably. I do not know particular transformer indeed,

Your not making any sense.  You say i fail miserably, with my assumption. ( which was that you dont' know about this specific transformer ), then you go on to say you dont' know this particular transformer in the very next sentence.      You need to live outside the datasheets a little, life is much more exciting and interesting there.        :-) 
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #30 on: December 26, 2018, 04:17:34 am »
Nice thing is because it's intended to be a bias tee, you can intentionally unbalance it in a test, run some current through it, and measure the saturation flux on the free winding(s)!

Just gotta order up some parts and put 'em to the function generator and scope.

Tim

And TDK have really conveniently provided a little dev board which makes it really easy.   ( is ordered but i'm still 3 weeks away from getting back home ).

worse case, its not suitable, best case i have a great solution
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #31 on: December 26, 2018, 03:34:14 pm »
Your not making any sense.  You say i fail miserably, with my assumption. ( which was that you dont' know about this specific transformer ), then you go on to say you dont' know this particular transformer in the very next sentence.      You need to live outside the datasheets a little, life is much more exciting and interesting there.        :-)

You better grow up and gain some real experience first. Then (perhaps) you will comprehend why I said what I said. Kids...  :palm:

Thanks so much for your valuable contributions. I'll keep it in mind.
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #32 on: December 26, 2018, 05:19:21 pm »
Thanks so much for your valuable contributions. I'll keep it in mind.

Maybe I was too harsh. It is not nice to hear "get a life" advice from obvious noob when you know your stuff & have 25 years background of EE, managed development of various 60W+ PoE-enabled devices. You shall just take my word and rest assured - 650mA trafo will not meet the specs at 1A, no matter it is Pulse I know or TDK I do not.

Once again thanks for your contribution.    I've just ordered the sample parts,  and designed a simple pcb so i can do some base evaluation, and had some intital feedback from TDK, which indicates that this is well worth pursuing.     
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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #33 on: December 26, 2018, 11:17:09 pm »
Maybe I was too harsh. It is not nice to hear "get a life" advice from obvious noob when you know your stuff & have 25 years background of EE, managed development of various 60W+ PoE-enabled devices.

As I've noted many times before on this forum... what do you expect, it's only free advice.  Just a bunch of hear-say from self-proclaimed experts (not leaving myself out here ;) ) until something actually gets made, and someone else actually gets paid. ;)

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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #34 on: December 27, 2018, 07:56:35 am »
Maybe I was too harsh. It is not nice to hear "get a life" advice from obvious noob when you know your stuff & have 25 years background of EE, managed development of various 60W+ PoE-enabled devices.

As I've noted many times before on this forum... what do you expect, it's only free advice.  Just a bunch of hear-say from self-proclaimed experts (not leaving myself out here ;) ) until something actually gets made, and someone else actually gets paid. ;)

Tim

One of the skills you need in life is to determine what 'free advice' you should take and which you should discard.     There is the weighting of information based on previous experience.  If somones given you good advice in the past, there is a good chance it will be good again. Theres the 'boast' factor.   Advice that is prefaced with  " i'm a ... with ... years of experience " normally is a good indicator to treat it with caution.   " X worked for me, becuase ..... " is a good indicator of something to look at deeper.    Advice that comes with a verifiable link... ( I got this from 'ABC' and it cost me $X )  ( www.x.com/abc/price.html) is good too.   

Its also never wise to assume the knowledge or expereince level of anyone asking a question.   You have no idea what they know. 
« Last Edit: December 27, 2018, 08:12:20 am by mrpackethead »
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #35 on: December 27, 2018, 09:37:54 pm »
So, this ALT4532 part is rated at 180uH @ 8mA.    With modern Phys ( well anything later than about 2004 ) we need > 120uH, to get BER of 10-8.    (NB: The 350uH @8mA came from ANSI X3.263: 1995,  to mitigate against Base Line Wandering, essentially a DC bias that occurs when you send a Long string of zeros or ones, which effectively set up a DC bias, however the modern phys all employ compensation schemes to get around this.  ).

The real question, and one that will only be answered by testing, is how much inductance will be lost as well increase the bias.    Will we drop below 120uH before we have a bias current >25mA.   

The cores are based on Ni-Zn ferrite material so they have both  high magnetic permeability and saturation flux density. And being machine manufactured, rather than hand wound.. theres a fighting chance here.
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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #36 on: December 27, 2018, 10:35:29 pm »
Hrm, MnZn ferrite would perform better, that's interesting.

Tim
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #37 on: December 28, 2018, 08:14:52 am »
Note that main source of DC bias current is TP (pair) DC resistance umbalance which is allowed by 802.3 to be <= 3%.
As you've said several times. Got anything new to add, though if repeating yourself over and over helps you, then i'm pleased to provide this thread as a public service to you.

Quote
You shall measure inductance loss @100 KHz using LCR meter/w bias option.

I'll read this as a language difference thing, but using the word "shall" really does make you look like some kind of dictator

Quote
It would be good idea to measure inductance loss at max temp as well. Temperature derating table (70oC @ 600mA and 85oC @ 500mA) does not look promising regarding "over current".

The the permability of Ni-Zn is very flat till about 120C.  A rise in temp, ( over a sensible range ) is not going to cause a significant reduction in inductance.    The derating is likely related to how hot the copper is going to get.    how far the inductance drops due to the DC bias is not yet clear.     

Quote
Those TDK Transformers are indeed nice, small and low profile, but if you ask me - I would not exceed specified 600mA.
I'm glad you've made that decision not to exceed 600mA in your design.    in 1961 a certain president did not have a datasheet that said they could go to the moon. but in 1969 they did.   ( they had a few opps moments on the way though ).   

Manufacturers give parts ratings so that they relaibly operate across a wide range of conditions,  and so they minimise their liability. And that is just fine.    Engineers can sometimes push past those things when they understand the constraints, and if you do not need to operate across a wide range of conditions, and can control the environments, you can sometimes do things that are 'outside' of the datasheet.   What you cant' do is expect thigns to work outside of the constraints of what are fundementals..  ( you can't just decide that gravity no longer applies or that you can have perpetual motion ).   

Quote
Did TDK FAE answer your questions?

One of the things that you really need to do is read forum posts carefully,   refer post #41

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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #38 on: December 28, 2018, 10:57:08 am »
Inductance vs temp and temp vs current
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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #39 on: December 28, 2018, 09:15:33 pm »
Anybody know why the inductance goes up as temp goes up.. ( and then drops of dramatically ). What is in play
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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #40 on: December 29, 2018, 01:32:24 am »
More temp leads to more activation of more ferromagnets, until it's too much, they get scattered randomly and the house of cards falls over (Curie temp).

The activation energy is all over the place, usually a blend is used (the exact mixture of Ni to Zn to Fe, and any dopants) to give some combination of properties for a purpose.  Some, you'll see multiple humps in the mu(T) plot, as different energy bands become active.

Which might imply, and quite rightly so, it is true -- that, as temperature goes up, Bsat goes down.  That is, there is more energy pushing the magnets out of alignment, so there are fewer able to line up with the applied field (if also more readily so -- high mu), even when driven heavily.

So it's actually very important to note that Tc is quite low for this material.  That means the drop in Bsat is nearby too, and it would be very easy to heat up this part, with DC current, enough to also spoil its DC imbalance handling.

Or if not due to DC heating alone at room temperature, then it will severely limit your ambient temp range.

I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.

Example:



Given the axes, this looks like it might be for nickel (it's from ResearchGate, I didn't read the article).  The curve is similar for other materials, adjusted for low-temp Bsat (left intercept) and zero-field Tc (bottom intercept).

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Offline ogden

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #41 on: December 29, 2018, 01:38:43 am »
I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.

Maybe they did not design those trafos for his application?
 

Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #42 on: December 29, 2018, 08:25:43 am »
I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.

Maybe they did not design those trafos for his application?

You once again seem to have missed the point.  We know what they were designed for. We know what the datasheet says.    What we dont' know are what the 'real' limits of 'were it will work to.     Please stay on topic, or find another thread to pollute.  Its not even about is this a good idea.   Its about understanding what will happen if you push past the datasheets limit.

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Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #43 on: December 29, 2018, 08:39:51 am »
More temp leads to more activation of more ferromagnets, until it's too much, they get scattered randomly and the house of cards falls over (Curie temp).
Right... That I would have never guessed or sumized.  RTheres some underlying physics i have never run into before. 

Quote
The activation energy is all over the place, usually a blend is used (the exact mixture of Ni to Zn to Fe, and any dopants) to give some combination of properties for a purpose.  Some, you'll see multiple humps in the mu(T) plot, as different energy bands become active.
As I did look at some of the various mixes they use for ferrites i did see some graphs like that.  ( see the one above for example, it only had one hump ).     Interesting stuff.

Quote
Which might imply, and quite rightly so, it is true -- that, as temperature goes up, Bsat goes down.  That is, there is more energy pushing the magnets out of alignment, so there are fewer able to line up with the applied field (if also more readily so -- high mu), even when driven heavily.So it's actually very important to note that Tc is quite low for this material.  That means the drop in Bsat is nearby too, and it would be very easy to heat up this part, with DC current, enough to also spoil its DC imbalance handling.
Or if not due to DC heating alone at room temperature, then it will severely limit your ambient temp range.
The TDK Engineer did'nt have all the lab testing results. ( theres a LOT more data that is not on the datasheet, but hopefuly I will get it soon, being Christmas/New Year its not a great time ).     It was suggested its been run up to 1000mA, but the thermal range was reduced.  The target market for these thigns are low profile servers, ( yes running on POE ). and i guess they dont' want to spend any energy on cooling.   I guess at 1000mA, its 'window' for being useful is greatly reduced and would be problematic for many of their key applications.

In several of the applications i'm going to be running, i'm likely to be pushing 20kW of power plus from a single location.   Active in rack cooling ( AC ) is not out of the question for those deployments.   





I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.

Example:



Given the axes, this looks like it might be for nickel (it's from ResearchGate, I didn't read the article).  The curve is similar for other materials, adjusted for low-temp Bsat (left intercept) and zero-field Tc (bottom intercept).

Tim
[/quote]
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Offline T3sl4co1l

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #44 on: December 29, 2018, 09:34:27 am »
Right... That I would have never guessed or sumized.  RTheres some underlying physics i have never run into before. 

Yeah, but at least that's not entirely your fault -- magnetism is... weird, even among physicists.  Real materials have all sorts of quirks they don't tell you about, that are just not very important in their dominant applications, and that aren't at all worth researching in depth.

Example, the traditional sigmoidal B-H curve is a lie for a lot of materials; it's actually a bit pinched in the middle, as reflected by the "initial permeability" parameter often seen.  This can be quite dramatic in some, like silicon steel where mu_i might be ~800 while mu_avg (at say Bpk = 1T) is closer to 10k or more.

Or the interplay between hysteresis loss, skin depth, Bsat and eddy currents in an induction heating application.  I saw one application where a deep case hardening was desired (~6mm deep) on a 6" ball (something like a ball-socket part).  Some simulations were attempted, with modest results, but including that many nonlinear material parameters was definitely pushing the capability of the simulator used.  The power supply ended up being a 3kHz machine (it was LOUD), uhh I forget if it was 150 or 300kW or what, and the exact profile (power level and duration) was dialed in by hand (run a part, slice it in half, take hardness readings around the edge; repeat..) as usual.

With better simulation tools, with better material characterization, with better physics in general -- perhaps the problem could be solvable fairly quickly for any arbitrary part within a class of shapes (since, you can't heat just anything, there are limitations on where fields will go).  But that would probably take decades of study, and no one's got time for that.  So we're left with a reasonably useful, yet still murky mystery that is magnets. :P

Tim
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Offline ogden

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #45 on: December 29, 2018, 11:08:59 am »
What we dont' know are what the 'real' limits of 'were it will work to.  Please stay on topic, or find another thread to pollute.  Its not even about is this a good idea.   Its about understanding what will happen if you push past the datasheets limit.

Well.. I already tried to bring your attention to thermal derating curve, but seems you were busy profiling me. You would want to calculate heat dissipated by transformers and chokes at target current (1A). Worth to consider slightly bigger magnetics having lower internal DC resistance, rather than spent BOM money and real estate in heat spreaders. Disclaimer: englisch is not my native language, please respect this fact.
« Last Edit: December 30, 2018, 01:07:43 am by ogden »
 

Offline mrpacketheadTopic starter

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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #46 on: January 14, 2019, 10:37:48 pm »
Some good news, at 1A current ( some 100mA over my target current ) the transformer does not overheat.   It does get warm. ( around 91C, some 71C over the ambient heat ).     I tryed attaching some heatsinks and it makes very little difference.  I put this down to that the wire is not well coupled thermally to the ferrite, and the ferrite itself has quite poor thermal conductivity ( roughly 100x less than aluminium ).

Some futher testing with forced air ( which is not an issue, as this is going to have fans anyway ), dropped the ferrite temp to just 54C.        The physical design of the transformer lends itself to being able to have forced air coming underneath it, via a cut out in the pcb.. This also means it does not require any additional parts. 

I am about to start testing for DC Bias and inductance versus temp.    With 30mA of bias it did not fall over.
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Re: "over current" use of a Pulse transformer - ( or an alternative )
« Reply #47 on: January 16, 2019, 03:36:58 am »
This is what i'm going to do to keep these cool.  ( it works in a hacked up test, now to more formally test on a designed pcb )

Air will be forced up from under the pcb, past the wire which is where the heat is.   This is going to be quite simple to implement
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