Example1 Thermal Analysis of IPM Motor

General

Temperature and torque characteristics of IPM motor (Interior Permanent Magnet Motor) are analyzed when the electricity is applied.
The model is a permanent magnet synchronous motor with magnets built in a rotor.
The analysis is coupled with the external circuit.
The homogenizing method is applied to simulate the layer structure of the electromagnetic plates of steel for the core.
Fast stabilizer is employed to make the magnetic field reach the steady state in short calculation time.
Temperature, torque and 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] Thermal Analysis [Watt]
Analysis Type	Magnetic field analysis: Transient Analysis Thermal analysis: Steady-State Analysis
Unit	mm
Options	Select External Circuit Coupling. Select Rotating machinery. [Conversion] Model Thickness: 30×10^-3[m] Select Partial Model. Number of Divisions of the Whole Model: 4 Circuit Configuration Number of Series: 1 Circuit Configuration Number of parallels: 1 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]

Number of Slide Mesh Divisions

Circumferential Division Angle: 1.0[deg]

Rotation per Step: 1[mesh]

Number of Slide Mesh Layers: 3

External circuit is as follows.

60[Hz] three-phase AC voltage is applied.

Set the Mesh Tab as follows.

Tab

Setting Item

Setting

Mesh

Meshing Setup

Automatically set the general mesh size: Deselect

General mesh size: 4[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 450, circumferential division angle is 1.0[deg], and rotation per step is 1[mesh], the rotation up to 450 degrees (=450*1.0*1) is analyzed.

The steps are set until the magnetic field reaches the steady state.

Tab

Setting Item

Setting

Transient Analysis

Time step

Automatic

Table

Number	Calculation steps	Output steps
1	450	1

Fast stabilizer is set up as follows to make the magnetic field reach the steady state in short calculation time.

Tab

Setting Item

Setting

Fast Stabilizer

Correction Method

Simplified Three-Phase AC TP-EEC Method

Coil Name on the External Circuit

U Coil: Circuit_Coil1

V Coil: Circuit_Coil2

W Coil: Circuit_Coil3

Graphical Objects

A rotor core and magnet are placed in the center. A stator and coils are placed around them.

This is a 3D model analysis. By utilizing the symmetry of the model, it is made to be a quarter model.

Half period rotation boundary (symmetry) is set.

“Ambient Air Creation” is selected.

Adiabatic boundary condition is set on the shaft and the gap between stator and rotor.

Body Attributes and Materials

Body Number/Type	Body Attribute Name	Material Name
28/Solid	coil_1	Cu
34/Solid	coil_2	Cu
35/Solid	coil_3	Cu
36/Solid	coil_4	Cu
37/Solid	coil_5	Cu
38/Solid	coil_6	Cu
55/Solid	mag	mag
45/Solid	stator_core	core
47/Solid	rotor_core	core

The body attribute is set up as follows.

For the core, the homogenizing method is selected to simulate the layered steel plates.

Body Attribute Name	Tab	Setting
coil_1	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil1 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_1	Stator/Rotor/Air	Stator
coil_2	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil1 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_2	Stator/Rotor/Air	Stator
coil_3	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil2 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_3	Stator/Rotor/Air	Stator
coil_4	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil2 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_4	Stator/Rotor/Air	Stator
coil_l5	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil3 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_l5	Stator/Rotor/Air	Stator
coil_6	Current	Waveform: External Circuit Coupling Coil Name on the Circuit: Circuit_Coil3 Turns: 35[Turns] Direction: Specify Inflow/Outflow Faces
coil_6	Stator/Rotor/Air	Stator
mag	Direction	Vector: X=1, Y=1, Z=0
mag	Stator/Rotor/Air	Rotor
rotor_core	Layer	Select Take layer into account Space: 97[%] Layer Direction Vector: X=0, Y=0, Z=1
rotor_core	Stator/Rotor/Air	Rotor
stator_core	Layer	Select Take layer into account Space: 97[%] Layer Direction Vector: X=0, Y=0, Z=1
stator_core	Stator/Rotor/Air	Stator

The material properties are set as follows.

Material Name

Tab

Properties

Conductivity

Conductivity Type: Conductor

Conductivity: 5.977×10^7[S/m]

Thermal Conductivity

Thermal Conductivity: 398[W/m/deg]

mag

Relative permeability

Material Type: Permanent Magnet

Magnet

Magnetization Characteristic Type: Linear

Magnetization Strength: 1.25

Relative Permeability: 1.05

Thermal Conductivity

Thermal Conductivity: 1[W/m/deg]

core

Electric Conductivity

Conductivity Type: Conductor

Conductivity: 1.7 x10^6[S/m]

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

Thermal Conductivity

Thermal Conductivity: 10[W/m/deg]

Boundary Conditions

“Natural convection (automatic calculation)” is set on the outer boundary condition (surrounding the motor in the case of the thermal analysis).

Half period symmetric boundary is set.

Adiabatic boundary condition is set on the shaft and the gap between stator and rotor.

Boundary Condition Name/Topology	Tab	Boundary Condition Type	Setting
Outer Boundary Condition *	Thermal	Heat Transfer/Ambient Radiation	Natural convection (automatic calculation) Room temperature: 25[deg]
shaft	Thermal	Adiabatic
rotor	Thermal	Adiabatic
stator	Thermal	Adiabatic
Symmetry	Symmetry/Continuity	Periodic	Rotation Period (Half Period)

To set Outer Boundary Condition, go to the [Model] tab

and click [Outer Boundary Condition] .

Results

The distribution of the magnetic flux density at 450 calculation steps.

The diagram below shows time-torque characteristics.

Transient state becomes stable at around 20[ms].

About 0.5[N*m] of torque is obtained.

The diagram below shows the temperature distribution of the stator.

In the steady state, it is around 100[deg].