Calculating Properties for Core Loss (BP Curve)

To be able to extract parameters from the loss characteristics (B-P Curve), you first set the Core Loss Model of the material to Electrical Steel or Power Ferrite as a material property in the View / EditMaterial window.

To calculate core loss properties for an electrical steel material:

1. Click Tools > Edit Libraries > Materials.

Alternatively, in the Project Manager tree, you can right-click Materials, under Definitions, and select Edit Libraries.

The Edit Libraries dialog box appears.

2. Click Add Material.
   The View / Edit Material dialog box appears.
3. In the Core Loss Model row, select Electrical Steel or Power Ferrite from the Value drop-down menu.

Additional parameters appear in the following table Core Loss Model (Kh, Kc, Ke, Y, Kdc, and Equiv. Cut Depth for electrical steel, and Cm, X, Y, Kdc, and Equiv. Cut Depth for power ferrite). For Electrical Steel, the Core Loss Coefficient selection in the Calculate Properties for drop-down menu at the bottom of the dialog box is also enabled. This allows the electrical steel coefficients Kh, Kc, Ke, Y, and Kdc, or the power ferrite coefficients Cm, X, Y, and Kdc to be derived from a manufacturer-provided core loss curve.

Note:

Both electrical steel and power ferrite core loss models are unsuitable when there is a wide frequency range. If the fitting error is too large, consider duplicating the curve data and reducing the number of curves to just the relevant frequencies. As an example, for the loss curves of a material with frequencies ranged from 50Hz to 1kHz, it is better to have two parameter sets, one for 50Hz, 60Hz, and 100Hz curves, and the other for 400Hz and 1kHz curves.

The fitting error can be used as a guide on whether the electrical steel or power ferrite model is more suitable.

Note:

The Kdc core loss quantity is not used for the AC Magnetic solution type.

4. If you selected Electrical Steel and have one measured BP curve at a fixed frequency, do the following:
1. Select Core Loss at One Frequency from the Calculate Properties for drop-down menu at the bottom of the dialog box.
   The BP Curve dialog box appears.
2. Do one of the following to specify a BP curve:
• Import the curve from a saved file.
• Enter the coordinates manually.
Note:

The accuracy in inputting the data for BP Curve for the electrical steel material has a significant effect on the correctness of analyses of electromagnetic devices. You should input the data for BP Curve according to accurate data provided by material manufacturers. Typically, core material suppliers provide the average loss over a cycle for a peak B, of sinusoidal nature. Therefore, for BP curve input in Maxwell, B(Tesla) should be peak, and P should be average.

Note:

Measured BP curves that are a linear function of (Bm)^Y will provide a more accurate curve fit.

3. Select the units in which the B-P curve is measured from the Core Loss Unit drop-down menu.
4. Enter values and select units for the following:
• Mass Density
• Frequency
• Thickness
• Conductivity

As the input data changes, the following parameters are dynamically updated with both the specified unit and the standard unit (w/m^3):

• Kh - Hysteresis Coefficient
• Kc - Classical Eddy Coefficient
• Ke - Excess Coefficient
• Y – Power of Bm for hysteresis core loss: Ph = Kh * f * Bm^Y
5. Click OK. The View / Edit Material dialog box reappears. The property values for Kh, Kc, Ke, and Y are updated as new default values.
5. If you selected Power Ferrite or Electrical Steel, and have measured frequency-dependent BP curves, do the following:
1. Select Core Loss versus Frequency from the Calculate Properties for drop-down menu at the bottom of the dialog box. The Core Loss versus Frequency dialog box appears.
2. Specify a frequency value in Edit box and click the Add button to add a frequency in the Frequency field.
3. Do one of the following to specify a BP curve for each specified frequency via Edit Dataset button in the Dataset field:
• Import curve from a saved file
• Enter coordinates manually
4. Select the units in which the BP curve is measured from the Core Loss Unit drop-down menu, and specify Mass Density when it is enabled.

As the input data changes, the following parameters are dynamically updated with both the specified unit and the standard unit (w/m^3):

• Cm – Coefficient of power-ferrite core loss
• X – Power of frequency for power-ferrite core loss
• Y – Power of Bm for power-ferrite core loss: P = Cm * f^X * Bm^Y
5. Click OK. The View / Edit Material dialog box reappears. The property values for Cm, X, and Y are updated as new default values.
Note:

The measured frequency-dependent BP curves can be used to extract parameters of the core loss model for either the Electrical Steel or the Power Ferrite material. Therefore, users can change the Loss Model inside the dialog box to see which model will have better regression curves. The regression error is displayed, and the displayed parameters change as the Loss Model changes. The smaller the regression error is, the better the regression curves match the measured curves.

6. Click OK to close the View / Edit Material dialog box.
7. Click OK to close the Edit Libraries dialog box.