Electronics > Projects, Designs, and Technical Stuff
"over current" use of a Pulse transformer - ( or an alternative )
T3sl4co1l:
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).
Tim
ogden:
--- Quote from: T3sl4co1l on December 29, 2018, 01:32:24 am ---I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.
--- End quote ---
Maybe they did not design those trafos for his application?
mrpackethead:
--- Quote from: ogden on December 29, 2018, 01:38:43 am ---
--- Quote from: T3sl4co1l on December 29, 2018, 01:32:24 am ---I'm rather surprised and perplexed why they went with NiZn here; it certainly makes it harder for your application.
--- End quote ---
Maybe they did not design those trafos for his application?
--- End quote ---
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.
mrpackethead:
--- Quote from: T3sl4co1l 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).
--- End quote ---
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.
--- End quote ---
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.
--- End quote ---
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]
T3sl4co1l:
--- Quote from: mrpackethead on December 29, 2018, 08:39:51 am ---Right... That I would have never guessed or sumized. RTheres some underlying physics i have never run into before.
--- End quote ---
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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