Multi-simulation: stator slot skewing effect at partial load, fixed-speed

Tutorial summary
Project name tuto_IPMSM_08
Machine name machine_IPMSM_A
Source project tuto_IPMSM_06
Description Same as tuto_IPMSM_06 but at partial load

In this example the no-load project tuto_test_IPMSM_06 is copied pasted in a new project named tuto_test_IPMSM_08 to find the optimal stator skew angle with respect to acoustic noise at partial load, fixed speed. Magnetic forces now involve both the fundamental field due to the magnets and due to the armature field.

The variable speed calculation based on load extrapolation is unactivated with

Workflow group (Variable speed tab)
Workflow group (Variable speed tab)

The partial load is activated using

Input.Simu.I0 = 10;
Input.Simu.Phi0 = pi/2;
Input.Simu.is_fixed_load_angle =1;
Input.Simu.is_mmfs = 1;

The speed is fixed at the resonance of the lamination breathing mode close to 6000 rpm:

Workflow group (Simulation tab)
Workflow group (Simulation tab)
Electromagnetic group (Assumption panel)
Electromagnetic group (Assumption panel)

The single input variable to be varied is the stator skew angle rate, expressed in stator slot pitch, given by


The skew rate is evenly varied from 0.8 to 1.2 stator slot pitch with 21 different values using

Input.Simu.types_var=[0]; %continuous variable
Input.Simu.types_val=[0]; % Value defined by interval
Input.Simu.type_sampling=[0]; % linspace sampling
Input.Simu.bds_contvar={[0.8 1.2]}; %Values between 0.8 and 1.2
Input.Simu.Nval_contvar=[21]; % 21 values
180. Setup of skew_rates variation
Setup of skew_rates variation

The output variable that is tracked during the sensitivity analysis is the nominal sound power level:

180. Workflow group (Sensitivity tab)
Workflow group (Sensitivity tab)

The default skew shape is linear, it is defined by the machine parameter


Finally the electromagnetic skewed model based on 7 slices is activated using

180. Numerical group (Magnetics tab)
Numerical group (Magnetics tab)
Input.Simu.type_skew = 2;          
Input.Simu.Nskew_slices = 7;

A the end of the calculation, the noise as a function of the skew rate can be plot using plot_MS_all_resp_var

Variable speed maximum noise level as a function of stator skew rate (partial load)
Variable speed maximum noise level as a function of stator skew rate (partial load)

One can see that the optimal skew is slightly above one stator slot pitch.

This confirms that the skew minimizing electromagneticall-excited acoustic noise and vibration is not necessarily one slot pitch.

MANATEE simulation software allows to find the best skew value depending on the force waves responsible for NVH and on the load state of the machine.