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# Example3Cogging Torque of Axial Gap Type Motor

General

• Axial gap type motor is analyzed.
Axial gap type motor consists of opposing disc type rotor and stator.
Cogging torque is analyzed which is incurred by the rotor’s rotation while no electricity is applied to the coils.

• Analysis function for axial gap motor is applied.

• The cogging torque and the magnetic flux density are solved.

• Unless specified in the list below, the default conditions will be applied.

### Analysis Conditions

 Item Setting Solver Magnetic Field Analysis [Luvens] Analysis Space 3D Analysis Type Transient Analysis Unit mm Options Select Rotating Machinery.   [Conversion] Select Partial Model. Number of Divisions of the Whole Model: 4 Select Convert the result to the whole model and output it.

The Rotating Machinery tab is set as follows.

 Tab Setting Item Setting Rotating Machinery Rotational Movement Select Constant Velocity Number of Rotations: 1800[r/min] Rotor’s Initial Rotation Position: 0[deg] Gap Type Axial Gap Number of Slide Mesh Divisions Circumferential Division Angle: 1.0[deg] Rotation per Step: 1[mesh] Number of Slide Mesh Layers: 3 Location of Slide Mesh Deselect Automatic calculation Rotor Type: Outer Rotor   [Gap Radius] Inner: 110×10^-3[m] Outer: 112×10^-3[m]   [Gap’s Coordinates in Axial Direction (Z Coordinate)] Top Side of Upper Gap: 52×10^-3[m] Bottom Side of Upper Gap: 50×10^-3[m] Top Side of Lower Gap: -50×10^-3[m] Bottom Side of Lower Gap: -52×10^-3[m] Division Size of Slide Mesh in the Axis Direction Divide at uniform interval with specified mesh size 10.0[mm]

Set the Mesh Tab as follows.

 Tab Setting Item Setting Mesh Meshing Setup Automatically set the general mesh size: Deselect General mesh size: 5[mm] Ambient Air Creation Select Create ambient air automatically Ambient Air Scale: 1.2

The Transient Analysis tab is set up as follows.

With the settings as below, number of steps is 90, circumferential division angle is 1.0[deg], and rotation per step is 1[mesh], the rotation up to 90 degrees (=90*1.0*1) is analyzed.

Tab

Setting Item

Setting

Transient Analysis

Time step

Automatic

Table

 Number Calculation steps Output steps 1 90 1

### Graphical Objects

A rotor core and coils are placed between stator cores and permanent magnets.

By utilizing the symmetry of the analysis model, it is made to be a quarter model.

“Ambient Air Creation” is selected.

• It is assumed that coil1, 2, and 3 are made of fine copper wires which will have little effect of induced current. So, “No” is selected for the Options of Induced Current.
If “Yes” is selected, the loss by induced current will impact the analysis and correct cogging torque will not be obtained.

### Body Attributes and Materials

 Body Number/Type Body Attribute Name Material Name 34/Solid coil1 Cu 35/Solid coil2 Cu 36/Solid coil3 Cu 33,37,38/Solid st_core core 20,31/Solid mag1 mag 19,30/Solid mag2 mag 23,32/Solid rt_core core

The material properties are set up as follows:

 Body Attribute Name Tab Settings coil1 Current Induced current: deselect Stator/Rotor/Air Stator coil2 Current Induced current: deselect Stator/Rotor/Air Stator coil3 Current Induced current: deselect Stator/Rotor/Air Stator mag1 Direction Vector: X=0, Y=0, Z=1 Stator/Rotor/Air Rotor mag2 Direction Vector: X=0, Y=0, Z=-1 Stator/Rotor/Air Rotor rt_core Stator/Rotor/Air Rotor st_core Stator/Rotor/Air Stator

The material properties are set as follows.

Material Name

Tab

Properties

Cu

Conductivity

Conductivity Type: Conductor

Conductivity: 5.977×10^7[S/m]

mag

Relative permeability

Material Type: Permanent Magnet

Magnet

Magnetization Characteristic Type: Linear

Magnetization Strength: 0.5[T]

Relative Permeability: 1.05

core

Permeability

Magnetization Characteristic Type: Select B-H curve

B-H Curve Table

 Magnetic Field [A/m] Magnetic Flux Density [T] 0 0 58 0.42 90 0.8 180 1.19 380 1.37 1100 1.48 2000 1.55 3000 1.608 11000 1.81 20000 1.91

### Boundary Conditions

Symmetric period boundary is set.

 Boundary Condition Name/Topology Tab Boundary Condition Type Settings Symmetry Symmetry/Continuity Periodic Rotation Period (1 period)

### Results

The distribution of the magnetic flux density at the rotation angle of 0[deg] is shown below.

The wave of cogging torque is shown as follows.

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