topic Re: Curve fitting problem - Core Loss Density Curves in Mathcad

Curve fitting problem - Core Loss Density Curves

Cornel — Tue, 20 Aug 2024 11:08:29 GMT

Hello,

Using this fit formula from below, how to determine a, b and c coefficients in such a way to fit the below plot Core Loss vs Flux density:

So, I think (but I do not know how to do) to read all the data points of each line (300kHz, 200kHz, etc) and then to make the curve fitting by using genfit Mathcad function, minerr or something like that.

Re: Curve fitting problem - Core Loss Density Curves

Cornel — Tue, 20 Aug 2024 15:13:35 GMT

For example below are the data points for the 3 lines: 300kHz, 200kHz, and 100kHz lines from above graph.

MCP10 file attached.

Both x and y axis are log scale.

Now we need to find the values of a, b and c coefficients in such a way to be able to generate these lines also with the above formula by fitting these curve with that given formula, by using genfit/mineer or something similar mathcad functions.

Re: Curve fitting problem - Core Loss Density Curves

terryhendicott — Tue, 20 Aug 2024 20:43:33 GMT

Hi,

Have done the first line for you.

Cheers

Terry

Re: Curve fitting problem - Core Loss Density Curves

Werner_E — Tue, 20 Aug 2024 23:03:16 GMT

If the goal is to find a separate fit for every frequency given, you could also use "line" to do so.

Here for 300kHz:

"B300" is the very same which you called "b". But you would get a slightly different value when you do the same for the other frequencies.

10^A300 is your a*f^c with f=300.

But I guess that you are looking for constant values a, b and c which are valid for any frequency.

To find these values I would suggest using a solve block with "minerr":

Thereafter you may define a function P which is only dependent on B and f and because with Prime we are using something similar to Mathcad, it may be a good idea to add correct units

Now you can use this function with any input value you like

and of course also for plotting with different frequencies

And as its a function with two arguments, you may also create a 3D-Plot if you like

Prime 10 sheet atached