# How to change calculation options of magnetic forces?

By default, magnetic forces are computed on the outer structure (stator, or rotor) of the electrical machine for the assessment of airborne acoustic noise due to magnetic forces. Additionnally, Maxwell tensor calculation on the inner structure of the electrical machine (resp. rotor, or stator) can be carried with the option Input.Simu.is_inner_force=1. The resulting Maxwell tensor can be post-processed with some specific post processing such as plot_Fr_fft2_in.

The airgap radius at which the calculation of Maxwell stress tensor is carried is by default in the middle of the airgap (between magnet top and lamination bore radius for PM machines). Another calculation radius can be enforced specifying in advanced mode Input.Simu.is_force_Rag=1 with new value of Input.Simu.Rag_forced.

The projection techniques of Maxwell tensor on the outer structure can also be changed in advanced mode. It is recommended to keep Input.Simu.type_projection=0.