General
Home / Examples / Magnetic Analysis (Luvens, Transient Analysis) / Example 2: SMP Motor Analysis (Current-Specified Input)
Torque characteristics of SPM motor (Surface Permanent Magnet Motor) is analyzed when the electricity is applied.
The model is a permanent magnet synchronous motor with magnets attached on the surface of a rotor.
The torque, magnetic flux density distribution, iron loss, cogging torque, and induced voltage are solved.
The Input is specified by current.
See Example 7 for the input by voltage.
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.
Unless specified in the list below, the default conditions will be applied.
In this example, a quarter period symmetric model is used for faster calculation.
A project of the full model is available as well.
Obtain a full model’s project file. (Save the project file before open)
Results will vary depending on Femtet version and the PC environment.
Item |
Settings |
Analysis Space |
2D |
Thickness in Depth Direction |
60 [mm] |
Unit |
mm |
Solver |
Magnetic Analysis [Luvens] |
Analysis Type |
Transient Analysis |
Options |
Select External Circuit Coupling. Select Rotating Machinery.
[Partial Model (Symmetric Model) Setting] Select Partial Model. Division Number: 4 [Conversion of external circuit I/O values] Select Convert Number of Series: 4 Number of Parallels: 1 Select Convert result to full model for output |
The Rotating Machinery tab is set as follows.
Tab |
Setting Item |
Settings |
Rotating Machinery |
Rotational Move |
Select Constant Velocity. Number of Rotations: 1800 [r/min] Rotor’s Initial Rotation Position: 0 [deg] |
Number of Sliding Mesh Divisions |
Circumferential Division Angle: 1.0 [deg] Rotational Quantity per Step: 1 [mesh] Number of Sliding Mesh Layers: 3 |
External circuit is as follows.
3-phase AC of 60 Hz and 5 A is applied.
The U phase is calculated with a function to [Search for power phase at the maximum torque].
As [Conversion of external circuit I/O values] is ON, the resistance value of the FEM coil is set to the phase resistance which is equivalent to a full model instead of a quarter model.
See [External Circuit Conversion] and [Example of External Circuit Conversion Setup] for the details of conversion.
Set the Mesh Tab as follows.
Tab |
Setting Item |
Settings |
Mesh |
Meshing Setup |
Set the general mesh size automatically : Deselect General Mesh Size: 1 [mm] |
Automatic Ambient Air Creation |
Select Create ambient air automatically. Ambient Air Scale: 1.2 |
The Transient Analysis tab is set up as follows.
The number of calculation steps is 180, circumferential division angle is 1.0 [deg], and rotational quantity per step is 1[mesh]. The rotation up to 180 degrees (=180*1.0*1) is analyzed.
It can be converted to the electric angle of 360 [deg] (=180*4/2) (mechanical angle x number of poles). One period of electric angle is analyzed.
As the input power is specified by current, the coil current is in the steady state from the beginning. The torque is also in the steady state.
To calculate the iron loss, it is necessary to set the timesteps for one period of electric angle in the steady state, and to define the iron loss characteristic for the material property.
Tab |
Setting Item |
Settings |
|||||
Transient Analysis |
Timestep |
Automatic |
|||||
Table |
|
A rotor core and magnet are placed in the center. A stator and coils are placed around them.
The motor has 4 poles and 24 slots.
This is a 2D model analysis.
By utilizing the symmetry of the analysis model, it is made to be a quarter model.
Rotation period boundary (symmetric) is set.
The full model is as follows.
Body Number/Type |
Body Attribute Name |
Material Name |
12/Sheet |
Mag |
NMX-S43SH_Hitachi Metal* |
11/Sheet |
Rotor |
35JN270_JFE Steel* |
28/Sheet |
Stator |
35JN270_JFE Steel* |
30/Sheet |
U1+ |
008_Cu * |
31/Sheet |
U1+ |
008_Cu * |
32/Sheet |
W1- |
008_Cu * |
33/Sheet |
W1- |
008_Cu * |
34/Sheet |
V1+ |
008_Cu * |
35/Sheet |
V1+ |
008_Cu * |
* Available from the material DB
The material properties are set up as follows:
The homogenizing method is applied to simulate the laminated plate of steel for the core.
Body Attribute Name |
Tab |
Settings |
Mag |
Direction |
Vector: X=1, Y=0, Z=1 |
Current |
Click Yes for induced current setting. |
|
Stator/Rotor/Air |
Rotor |
|
Rotor |
Layer |
Select Take into account layer Space Factor: 97 [%] Layer Vector: X=0, Y=1, Z=0 |
Stator/Rotor/Air |
Rotor |
|
Stator |
Layer |
Select Take layer into account Space Factor: 97 [%] Layer Vector: X=0, Y=1, Z=0 |
Stator/Rotor/Air |
Stator |
|
U1+ |
Current |
Waveform: External Circuit Coupling Coil Name on the Circuit: U1 Turns: 35 [Turns] Direction: +Y Direction |
Stator/Rotor/Air |
Stator |
|
V1+ |
Current |
Waveform: External Circuit Coupling Coil Name on the Circuit: V1 Turns: 35 [Turns] Direction: +Y Direction |
Stator/Rotor/Air |
Stator |
|
W1- |
Current |
Waveform: External Circuit Coupling Coil Name on the Circuit: W1 Turns: 35 [Turns] Direction: - Y Direction |
Stator/Rotor/Air |
Stator |
Half period symmetric boundary is set.
Boundary Condition Name/Topology |
Tab |
Boundary Condition Type |
Settings |
Symmetric |
Symmetry/Continuity |
Periodic |
Rotation Period (Half Period) |
The distribution of the magnetic flux density and magnetic flux lines at the rotation angle of 0 [deg] are shown below.
The diagram below shows rotation angle-torque characteristics. It is output to "Torque [N*m]" of the result table.
About 3.4 [N*m] of torque is obtained.
The torque is in the steady state from 0 [deg] as the current source is used.
The losses are listed in the table of [Loss [W] (referring to value over 1 period from the final step)].
By setting the current to 0 for the power of the external circuit, the cogging torque and the induced voltage with no load can be calculated.
(Refer to the analysis model "No Load")
The waveform of cogging torque is shown as follows.
The induced voltage waveforms are as follows.
N-T characteristics and I-T characteristics are calculated by a function of [Motor characteristics analysis].
The inductance (Ld and Lq) characteristics are calculated by a function of [Calculation of Motor LD and LQ] tab.