Coefficients in core losses calculation

[wijono]

Hi All,
I am working in a design of permanent machines. I use FEA program. In the core losses calculation, the program needs the hysteresis, eddy current and excess coefficients.
The core is silicon steel lamination 50H470 from Nippon steel.
Is there anybody knows values of those coefficients or URL links about that.
Thanks for help.

 

[ScottyUK]

I'm gonna take a guess here and say that Nippon Steel probably have that information. Why can't they give you the values?


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I don't have an attitude problem. You have a perception problem...

 

[wijono]

They give us only the BH-curve and core-loss profiles for some frequencies. In the transient analysis used in the FEA simulation, all three coefficients are required, instead of the loss profile. In addition, the transient simulation does not involve the frequency.

Thanks for response

 

[electricuwe]

With the coreloss curves at different frequencies you can choose some data points in range under consideration, set up a sufficient number of equations and calculate all the required coefficients.

 

[wijono]

Hi electricuwe and all

Thank you for suggestion. Now, I am doing with that.
For every frequency, I got one set of coefficients. So that, the coefficients now become variables.
Perhaps, I have to separate those coefficients into a low frequency and a high frequency ranges. It is assumed that in the low frequency range, the permanent magnet flux - and its "slow" changing - can be included. It is required since the transient simulation works in the time domain.
Is that assumption reasonable?

Thanks.

 

[Clyde38]

Excerpts from USS application guide:

Core loss separation:
In some design applications, it is of interest to separate the total core loss into two components, the hysteresis loss, Ph, and the eddy-current loss, Pe. Since the hysteresis loss per cycle of the excitation field is proportional to the area of the static hysteresis loop, it is convenient to relate the hysteresis loss to static loop parameters such as coercive force, Hc, and residual induction Br. Specifically, the hysteresis power loss is:


Ph=0.01445(?fBrHc) watts per pound
D

Where:
f is the excitation frequency in Hz
Br is the residual induction in kilogausses
Hc is the coercive force in oersteds
D is the density in grams per cubic centimeter
? is the hysteresis loss factor, is the ration of the actual hysteresis losses to the area of a square hysteresis loop passing through Br and Hc.

Eddy-current losses are due to energy dissipated by circulating currents induced in the core by the alternating magnetization. For laminations, eddy-current losses can be obtained from the expression:

Pe=.4818(? B²mt²f²) watts per pound
?D

Where:
Bm is the maximum magnetic indudction in kilogauss
T is the laminations thickness in inches
? is the electrical Resistivity in microhm-cm
D is the density in grams per cubic centimeter
? is the so-called anomalous loss factor

Anomalous losses are introduced to account for differences between observed eddy-current losses and those calculated for the classical electrodynamics (in which case ?=1), and are usually attributed to magnetic domain wall effects. The deviation of the anomalous loss factor from the classical value of one increases with decreasing core loss and sheet thickness. (?=1 to ~ 2.25).

Total core loss is Ph + Pe

 

[electricuwe]

Thanks Clyde38, you already answered the open question.

With that approach, there should be a consistent set of coeeficients suitable to be entered into the simulation software.

 

[wijono]

Thanks electricuwe and Clyde38.

Yes, in the finite element analysis simulation, especially in the transient mode simulation, the coreloss calculation is based on the object element, therefore the common equation can not be directly used.

In this time I decided to use the low frequency coreloss curve provided by the manufacturer, i.e. 100 Hz, as my machine will be operated, and to use the FEA program feature to find the coefficients. The result is that Kh and Kc are non zero and Ke is zero. The total coreloss seems to be acceptable. With the material coreloss density of 5-6 watt/kg at 1 Tesla, the maximum flux density is designed to be 1.2-1.5 Tesla, and the core is swept by the permanent magnet flux at around one half of its volume in every cycle, so the core of 10kg will dissipate around 30watt, in average.

Thanks, all.