Core losses in dual big inductors

Oops. Just came back, the bill will be painful but not written yet. Because they took me in as an emergency and didn't fire up the server.

Best dentist we ever had. But he is well into his 70's and when he ever retires I don't know what we are going to do.

Mine usually go directly from simulator to CAD and then to fab. So we get complete proto boards back. On simple designs that's usually it, goes into production like that after testing.

I found that the simulations are darn close to the real-life results later, except you never quite know how hot the core will get. This time it was a bit much but it was a complicated design.

I'm quite pain tolerant, which is a good thing, since most anesthetics don't do much for me. It was first noticed when I had my tonsils out at age 7... they couldn't put me out with Ether... had to use Morphine ;-)

Fortunately, modern anesthetics seem to work OK. I had my left eye lens changed out a few weeks ago... didn't feel a thing.

And I tore a rotator cuff reaching out too far to lift a propane tank a couple of months ago :-( Finally gave up on it healing itself and had an MRI last week... definitely torn, plus some old age degradation :-( They'll patch that orthoscopically. ...Jim Thompson

I'm pondering that it may be possible to make a subcircuit that will come quite close... without having any complex core model available.

We know that the losses are proportional to the flux change and to the frequency to some power. So maybe a few measurements on a core to get the coefficients, then create a subcircuit that has an extra pin that shows power dissipated. (We'd still have the thermal resistance issue to ponder.)

Most of the switchers I've made are really high power, like 5V/400A, with fist-sized Ferroxcube E-E transformers, or very small... like

Cool, in all cases... as I've told about the "cool" one that had 400V P-P on the mounting flag ;-) ...Jim Thompson

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As for the simulation of magnetics in PSpice, the magnetics simulation tool allows for advanced simulation of Magnetics and Ferroxcube parts (other th ird party manufactors can be added) including detailed information on bobbi n and even insulation materials. It even has a wizard when creating the mod el the will check against fill factor and guide through the construction of the part if needed.

Cheers

Klaus

I know. I was just pondering how to make a more universal tool.

Though some have said there's a "Chan" model in LTspice. Is Joerg overlooking a built-in solution for those who adhere to "free" ?:-) ...Jim Thompson

At a past job, there were a couple of boards that had mods that were unobvious to the naked eye but that made them Different than production. I wrote "Engineering" on the RF shield cans in Sharpie. I may have also written it on the board, too... I wouldn't put it past one manager to swap graffiti-free shield cans onto the board so he could ship it. This board was the size of one of your VME boards, though, and had several

I threatened to paint the front panels pink, but I never got brave enough to. One of my co-workers liked to run engineering boards without a front panel if he could get away with it.

I have heard of, but not personally seen, somebody soldering a few "mistake" wires onto a board... they went from +5 V to +5 V or ground to ground, but they were allegedly enough to stop the boards from being shipped.

Matt Roberds

A lot of the early bobbin cores for SMD were/are pressed iron dust, that really weren't meant for large deltaB. This is usually the reason why loss isn't specified. The shapes aren't cheaply obtainable in ferrite.

If the material is recognizable, then yes, core loss is a standard specification.

I'm not a fan of some of the representations made for core loss calculation formulas, but Siemens/Epcos, Philips/Ferroxcube and MagneticsInc are pretty good at coming up with coefficients that correspond to the earlier work of Snelling for ferrites. This is the most common material used in serious HF magnetics experiencing larger AC flux excursions.

Magnetics has tried to extend this to some of the higher flux, lower permeability powder cores, but has yet to present proper ferrite/powder correlation.

A search for "Magnetics-Ferrite-Core-Loss-Equations" will find a spreadsheet that might be of interest.

RL

Quick and dirty simulation to plot B-H loop of EP7 core in H5A ferrite. Ungapped, alter parameter LG for required gap (in meters):

Use the plot file (at end) to set plot to read directly in amp/meter and tesla.

Version 4 SHEET 1 1008 680 WIRE 192 80 -32 80 WIRE 448 80 304 80 WIRE 512 80 448 80 WIRE 304 96 304 80 WIRE 448 96 448 80 WIRE -32 128 -32 80 WIRE 192 128 192 80 WIRE -32 256 -32 208 WIRE 80 256 -32 256 WIRE 192 256 192 208 WIRE 192 256 80 256 WIRE 80 288 80 256 FLAG 80 288 0 FLAG 512 80 OUT IOPIN 512 80 Out FLAG 304 176 0 FLAG 448 176 0 SYMBOL ind 176 112 R0 WINDOW 3 29 104 Left 2 SYMATTR Value Hc=8 Br=100e-3 Bs=410e-3 Lm=15.7e-3 Lg=0 A=10.3e-6 N=10 SYMATTR InstName L1 SYMBOL bv 304 80 R0 SYMATTR InstName B1 SYMATTR Value V=idt(v(n001)) SYMBOL current -32 208 R180 WINDOW 0 24 80 Left 2 WINDOW 3 -106 36 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName I1 SYMATTR Value SINE(0 .5 1000) SYMBOL res 432 80 R0 SYMATTR InstName RB1 SYMATTR Value 1meg TEXT -40 296 Left 2 !.tran 0 2m 0 100n

Plot File:

The "Chan" model in LTSpice only works for isolated inductors - you can't directly couple such an inductor to other inductors to simulate a transformer.

Thanks, Fred!

Am I correct in assuming, no loop, no losses?

Does saturation have a loss mechanism? ...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

It is, but that only helps once you know the losses.

I suppose one could go backwards once a particular inductor has been tested (how many watts is 50C temp rise?), assuming AC+DC copper losses can be teased apart. Destructive testing of a part would be informative with regards to winding construction (wire diameter, turns spacing, layers; skin depth, proximity effect; AC/DC resistance ratio), and would also tell number of turns and core area.

Tim

Yes. I've got something similar, that does hysteresis loss. I'll dig it out and post it.

I find that I can lose semiconductors when magnetics saturate !

boB

No, no, you don't really lose them. They just transfer from a solid state into a vapor state but they are still there, somehow ...

:-)

I lose semoconductors just trying to get them from the tube onto the PC board.

Use this .plt file, with the model I already posted, giving losses in the inductor.

Make sure that you set rser=0 l-(

Play with the Chan model constants, you'll find that losses are due to coercivity, rather than saturation. Ignore the Spice artifact spikes (smaller maxstep helps).

Hysteresis loss isn't the whole enchilada, by any means.

Plot file:

Thanks, Fred, I'll get it a twirl.

I also found a paper by Hermann Haus and Jim Melcher (one of my grad student mentors while I was at MIT) which thoroughly discusses the problem. I'll see if I can't set the math to a behavioral model that will work with all flavors of Spice. ...Jim Thompson