Multi-simulation: rotor stepped skew effect at partial load, fixed-speed

Tutorial summary
Project name tuto_IPMSM_07
Machine name machine_IPMSM_A
Source project tuto_IPMSM_05
Description Same as tuto_IPMSM_05 in partial load

In this example the no-load project tuto_IPMSM_05_test is copied pasted in a new project named tuto_IPMSM_07_test to find the optimal rotor 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 spectrogram synthesization is unactivated with

Input.Simu.is_spectro_synthesis=0;
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;

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

Input.Simu.N0=6407;
Workflow group (Simulation tab)
Workflow group (Simulation tab)
Input.Simu.is_mmfs = 1;
Electromagnetic group (Assumption panel)
Electromagnetic group (Assumption panel)

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

Input.Simu.names_var={'skew_rater'};

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 in [0.8,1.2]
Input.Simu.Nval_contvar=[21]; % 21 values
Setup of skew_rater variation
Setup of skew_rater variation

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

Input.Simu.names_resp={'LwrA'};
Workflow group (Sensitivity tab)
Workflow group (Sensitivity tab)

The default skew shape is linear, it is defined by the machine parameter Input.Geometry.type_skew_geoR. Finally the electromagnetic skewed model based on 5 magnet segments is activated using

Numerical group (Magnetics tab)
Numerical group (Magnetics tab)
Input.Simu.type_skew = 2;          
Input.Simu.Nskew_slices = 5;  

The noise as a function of the skew rate can be plot using plot_MS_all_resp_var

Evolution of LwrA as a function of skew_rater
Evolution of LwrA as a function of skew_rater

One can see that the optimal skew is slightly above one stator slot pitch, which confirms that the optimal skew rate for vibroacoustics depends on the load state.

The optimal skew value considering all the load points at variable speed can be easily obtained with MANATEE, allowing to define the best magnet inclination angle on the whole torque speed curve considering both torque ripple and acoustic noise criteria.

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