Calculating the Properties for a Nonlinear Permanent Magnet

Nonlinear permanent magnet properties may be specified in one of two ways:

Input a B-H curve directly as follows:

Note: You can model multiple temperature dependencies of a nonlinear material property by providing two or more temperature-dependent B-H curves. Refer to Specifying B-H Curves for Nonlinear Relative Permeability for detailed information.
  1. Click the View/Edit Materials… button in the Edit Libraries window.

    2. The View/Edit Material window appears.

  2. To define the nonlinear B-H curve, set the Relative Permeability Type to Nonlinear:

    A B-H Curve button appears in the nonlinear property’s Value column.

  3. Input the B-H curve by clicking the B-H Curve button in the property Value column.

    4. This opens the BH Curve dialog box in which you can input (or modify) curve data. (Refer to Adding Datasets for general information on working with datasets.)

    • For a Normal B-H curve, the slope of the curve can not be less than that of free space anywhere along the curve.
    • For an Intrinsic B-H curve, the slope of the curve can not be less than 0.
    Note:
    • The Intrinsic B-H curve is supported only in Maxwell 2D/3D magnetostatic and transient design types. A material property defined using an Intrinsic BH curve will fail validation check in all the other product/design types.
    • When an Intrinsic B-H curve is added, the Relative Permeability Value button label changes to Bi-H Curve as visual indication of the type of curve currently defined for the material.

    When you click OK in the dialog box, an error message displays if a slope is out of tolerance, identifying the data points between which the slope is less than that of free space.

    The operations to input a nonlinear demagnetization curve are the same as entering a B-H curve for Steel material. When a B-H curve goes through the second quadrant or third quadrant, the curve is treated as a demagnetization curve.

  4. To model a single temperature dependency for a nonlinear permanent magnet you must
    • Use an Intrinsic B-H curve to model the Relative Permeability
    • Specify a thermal modifier for both Relative Permeability and the Magnitude of Magnetic Coercivity. Apply a thermal modifier by selecting the Thermal Modifier check box. Checking this box causes the Thermal Modifier column to display at the right side of the Properties of the Material table. Selecting Edit rather than None causes display of the Edit Thermal Modifier dialog.

      Note: You can model multiple temperature dependencies of a nonlinear material property by providing two or more temperature-dependent BH curves. Refer to Specifying BH Curves for Nonlinear Relative Permeability for detailed information.

Creating a Nonlinear B-H Curve with Four Parameters

Alternatively, a nonlinear B-H curve can be modeled by the following four parameters:

From the View/Edit Materials window:

  1. Set the Relative Permeability to Nonlinear.

    2. This enables the Calculate Properties for... drop-down menu at the bottom of the window.

  2. Select Nonlinear Permanent Magnet from the drop-down menu.

    3. This displays the Properties for Nonlinear Permanent Magnet dialog box, which contains the following fields into which you enter the appropriate values.


    Mur

    Provide a value for relative permeability.

    Hc

    Coercive field force Hc in the units specified. Provide a value and select units from the drop-down menu.

    Br

    Residual flux density Br in Tesla.

    If enabled, provide a value and select units from the drop-down menu.

    BHmax

    Maximum magnetic energy product (BH)max

    If enabled, provide a value and select units form the drop-down menu.

  3. Click OK to close the dialog box and return to the View/Edit Materials window.

The values for Relative Permeability and Magnitude under Magnetic Coercivity are updated as new default values, and the existing B-H curve is updated based on the new values of these parameters.

Related Topics 

Nonlinear vs. Linear Permanent Magnets

Characteristics and Main Parameters of Permanent-Magnetic Materials

Calculating the Properties for a Permanent Magnet

Specifying B-H Curves for Nonlinear Relative Permeability

Temperature-Dependent Nonlinear Permanent Magnets

Irreversible Demagnetization Due to Temperature Change