Tutorial summary | |
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Project name | tuto_BPMSM_05 |

Machine name | machine_BPMSM_A |

Source project | tuto_BPMSM_02 |

Description | Sensitivity study on rotor skew |

In this example the open-circuit project tuto_BPMSM_02_test is copied pasted in a new project named tuto_BPMSM_05_test to find the optimal magnet skew angle with respect to acoustic noise at variable speed. The sensivity analysis is activated by using

`Input.Simu.type_sensitivity = 1;`

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 to 1.2 stator slot pitch with 27 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 1.2]}; %Values between 0 and 1.2

Input.Simu.Nval_contvar=[27]; % 20 values

The output variable that is tracked during the sensitivity analysis is the maximum sound power level calculated from N0_min to N0_max rpm:

`Input.Simu.names_resp={'LwrA_max'};`

In the GUI all these parameters are gathered in the Workflow group / Sensitivity tab. You have to click "Add Input" to set the variation of skew_rater:

Then you have to click on "Add Output" to add Lwra_max:

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

`Input.Simu.type_skew = 2; `

Input.Simu.Nskew_slices = 5;

The maximum noise and cogging torque levels as a function of the skew rate can be plot using plot_MS_all_resp_var

**Effect of the rotor skew rate on the maximum sound power level radiated by a variable-speed PMSM (MANATEE software output)**

One can see that the maximum noise in open-circuit variable speed condition, which is dominated by a zero-th wavenumber, is minimized close to (4/5)=0.8 stator slot pitch together with cogging torque.

The optimal skew angle depends on the type of the force wave responsible for noise and depends on the load condition, so **the optimal skew rate is not always (N-1)/N stator slot pitch** for N magnet segments.

This simulation only takes a few sconds so MANATEE software allows to quickly optimize the skew geometry in terms of torque ripple, acoustic noise & vibrations and electromagnetic performances.