Example10 120-Degree Conduction DC Motor (with Switches)

General

• The basic characteristics of a 120-degree conduction DC brushless motor are analyzed.

• The torque, magnetic flux density distribution, iron loss, are solved.

• 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.

Show Results

The Rotating Machinery tab is set as follows.

External circuit is as follows.

The 120-degree conduction (square-wave drive) is generated by the DC power and the switches.

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.

See [External Circuit Conversion] and [Example of External Circuit Conversion Setup] for the details of conversion.

Of the six switches in the three-phase bridge inverter circuit, one phase is in the high side,

another phase is in the low side, ant the rest is switched off.

The timing for switching is as follow.

Set the Mesh Tab as follows.

The Transient Analysis tab is set up as follows.

The number of 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.

• As the input is by voltage for this model, it will take some time for the coil current and the torque to reach 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.

Model

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

The motor has 12 poles and 18 slots.

This is a 2D model analysis.

By utilizing the symmetry, the model is 1/6 period symmetric.

Rotation period boundary (symmetric) is set.

Body Attributes and Materials

* Available from the material DB

The body attribute is set up as follows.

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

The material properties are set as follows.

* [50H350_Nippon Steel] from the Material DB is used for the core.

The values for the B-H curve and the iron loss table are taken from the database. The iron loss calculation type is manually changed to [Frequency Analysis (FFT)] from [Amplitude].
Although the iron loss calculation by the iron loss table is executed by comparing the the amplitude of the frequency and the magnetic flux density with the table,
if the sine wave is not used, the harmonic component of the iron loss cannot be taken into account unless the frequency analysis (FFT) is performed.
See Permeability tab for detail.

Boundary Condition

Half period symmetric boundary is set.

Results

The below are the results.

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

The wave of torque is shown as follows. It is output to “Torque [N*m]” of the result table.

The torque reaches the steady state at 90 [deg].

The losses are listed in the table of [Loss [W] (referring to value over 1 period from the final step)].