The set-up of the variable speed simulation at open-circuit of the surface permanent magnet machine has already been presented in the article simulation setup, the corresponding simulation project is *tuto_SPMSM_01*.

In this new project *tuto_SPMSM_02* the permeance / mmf electromagnetic model, which only calculates the airgap radial flux density component, is activated using

`Input.Simu.type_Bmodel = 0;`

An exact analytical model is used to calculate the rotor magnetomotive force for different magnetization patterns (radial, parallel, or Hallbach).

The airgap flux density spatial distribution can be plotted with plot_B_space :

One can notice that the tangential part of the flux is missing contrary to what is found using subdomain models.

The accuracy of the permeance/mmf model can be improved without significant calculation time increase by quantifying the slotting permeance using FEMM. The stator slot permeance can be displayed using plot_Per_slot :

The calculation of the stator slot permeance using FEMM can be activated using

`Input.Simu.type_perm_modelS = 2;`

When running the simulation a FEMM model of a single stator slot with an arbitary mmf source is created to calculate numerically the permeance:

You can run the basic post processings and variable speed post processings showed at the beginning of the tutorial. In particular the commands plot_VS_ASWL_modal_cont and plot_VS_ASWL_sonagram are very useful and give the following results:

The** permeance / mmf model does not account for the tangential flux density harmonics** that have a significant vibroacoustic role in some topologies. However the permeance / mmf model can easily account for faults (eccentricities, demagnetization, pole shifting, etc).

To include the tangential component of the flux in the model it is recommended to use the subdomain method as in the following tutorial.