X-MINING Polar anisotropic SmFeN magnets simulation with 8 poles outer circumference
[Analysis case: Magnetic field analysis simulation]

• You want to reduce the vibration without changing the torque of the motor.
• You want to use anisotropic magnets with high magnetic force instead of isotropic magnets.
• You don’t know how to control the surface flux waveform with anisotropic magnets?
• You want to simulate the characteristics of a motor using anisotropic magnets.

It is necessary to align the orientation of the crystals by applying a magnetic field during molding, because Wellmax^TM SmFeN magnets are anisotropic magnetic materials.
We introduce how to configurate the magnetic orientations using the magnetic field analysis software “JMAG”.

Step 1: Orientation analysis

Create several models of molds with permanent magnets and calculate the orientation of the Wellmax^TM material during molding.

Step 2: Surface magnetic flux density analysis

Calculate the waveform of the surface flux density of the magnet with magnetic orientations obtained in Step1.

Model: Magnet to simulate magnetic field analysis

・Shape of the magnet: Φ30×Φ25×L20 (mm)
・Magnetic matrial: Wellmax^TM-S3A12M
・Magnetic poles: 8poles in outer surface
・Anisotropic type: Polar
・Specifications: Surface magnetic flux density≧ 0.25T (Gap=0.02mm from outside magnet surface, Center of magnet height)
・Waveform: sinusoidal wave
・Accessories: None

Figure １　Shape of magnet

Analytical model

The orientation model was constructed using two permanent magnets (orientation magnets) per magnet pole, and magnetic field analysis was performed by changing the angle of the orientation magnets and the materials of the mold components.
The angle of the two orientation magnets was adjusted starting from the parallel orientation pattern (Case-1), which has a square wave shape, to the opposing orientation pattern (Cases-2 to 6), which has a higher peak, to search for a configuration that satisfies the required characteristics (peak and shape).

Figure 2 Example of magnetic circuit design

Result of analysis

The direction and magnitude of magnetization of Wellmax^TM magnetic material filled in the cavity in each orientation model were calculated using the magnetic field analysis software “JMAG”.

Figure 3 Example of vector diagram in cavity

Analytical model

We used magnetic field analysis to simulate the waveform of the surface flux density of each magnet with the orientation obtained in Step 1 for the Wellmax^TM material.

Result of analysis

The peak value of the surface magnetic flux density, the area of one pole, and the odd-order component values of the waveforms of the magnets simulated by the magnetic field analysis for each orientation model were compared.

Figure 4 Example of vector diagram of magnet analysis results based on each orientation

Figure 5 Surface magnetic flux density waveforms of magnets in six orientation model patterns

Figure 6 Peak values of magnet surface flux density waveforms, area of one pole, and FFT analysis results for six orientation model patterns.

We have studied the configuration of orientation molds that satisfy the required characteristics of SmFeN injection molded anisotropic bonded magnetic material (Wellmax^TM material) by magnetic field analysis simulation.
The six orientation patterns studied all satisfied the peak value of the magnet’s surface magnetic flux density, and three of the patterns had a surface magnetic flux density waveform with a first-order component exceeding 90%, close to the sinusoidal waveform required by the waveform.
Two more orientation configurations that meet the peak value and waveform requirements have low 3rd and 5th order components of the waveform.
For this reason, we considered the combination of either of these orientation configurations with the Wellmax^TM material to be a good choice.