PCogging Torque of Permanent Magnet Motors
The overlay motor library in Flux software is known for its ease of use and powerful parameterization capabilities. Given the limited available information on overlay modeling, this paper will apply overlay modeling for parametric analysis of the cogging torque in a 4-pole, 12-slot permanent magnet motor.
Modeling
Load the motor model as shown in Figure 1.
- Figure 1: Select the first option, which is the inner rotor brushless permanent magnet motor.
- Figure 2: Once loaded, as shown in Figure 3, right-click to create a new motor template.
- Figure 3: The motor parameters are set as shown in Figures 4–9.
After the settings are completed, click “OK” as shown in Figure 10, and close the template. The modeling process is now finished.
Solution Type and Physical Properties Setup
This motor model simulation is a transient solution, as shown in Figure 11.
The effective motor length is 50 mm, as shown in Figure 12.
- Figure 13: Steady-state analysis begins.
Material Properties Setup
The materials used in this example mainly include the permanent magnet and core materials.
- Figure 14: New material is created.
- Figure 15: Settings for the permanent magnet materials.
- Figure 16: The silicon steel sheets are selected from the built-in materials library.
- Figure 17: Import the 27035A silicon steel sheet.
Mechanical Properties Setup
In this example, the mechanical properties mainly include the stator and rotor parts. The rotor settings are shown in Figures 18–20.
- Figure 19–20: The rotor’s initial position is 0, and the rotational speed is 1 mechanical degree per second.
The stator settings are shown in Figures 21–22.
- Figure 23–24: A line region needs to be created as the outermost layer of the motor. Assign it as a magnetic insulation structure, meaning all magnetic field lines are closed along the core without leakage.
Assignment of Properties
The software automatically assigns face regions, and you only need to link the material and mechanical properties to each region.
- Figure 25: Permanent magnet.
- Figure 26–27: Double-click the region for the permanent magnet, i.e., MAGNET_1_POLE_1.
Slot Setup
- Figures 28–29: The rotor settings.
- Figures 30–31: Other parts are not displayed. Click on each part of the motor and set the material and mechanical properties for the two phases.
After linking all the material properties, the magnetization of the permanent magnet is set, as shown in Figures 32–33.
- Figure 33: Radial magnetization.
Press “Ctrl + M” or select “Mesh Domain” from the menu bar to perform the meshing, as shown in Figure 34.
Solver Setup
- Figure 35: Solver setup.
- Figure 36: The cogging torque cycle is one mechanical angle of 30 degrees. In this case, the motor rotates for one cogging torque period.
The tooth thickness is parameterized in this example, varying from 4 mm to 7 mm, with a step size of 0.1 mm. Save the model before solving.
- Figure 37: Parameterization settings.
Solving
Go to the menu bar, select “Solving” → “Solve.”
- Figures 38–39: Simulation complete.
Post-Processing
- Figure 40: Magnetic flux density distribution at a tooth thickness of 7 mm and an angle of 12°.
- Figures 41–42: Cogging torque ripple.
Displaying the Relationship Between Tooth Thickness and Magnetic Flux Density
Create a new sensor, as shown in Figures 43–45.
Select the desired points from the figure, as shown in Figure 46.
- Figure 47: Display the curve.
Select tooth thickness as the horizontal axis, as shown in Figure 49.
- Figure 50: The curve of the magnetic flux density at the selected point versus tooth thickness.
- Figures 51–52: Magnetic flux density cloud plot for tooth thicknesses of 5 mm and 7 mm, respectively.
