2.2.2. Slot Openings in the Stator and Rotor

The slot openings in the stator and rotor can be considered in the form of a permeance function Λ for a better description of the field characteristics [11,12]. Among other things, this increases the accuracy of the calculation of the iron losses and the distribution of forces in the machine. The permeance function is described as the product of the permeance functions of stator and rotor, which can be represented as infinite complex Fourier series due to the periodicity [4,11,12].

Accounting for these effects in combination with multiple armature reaction leads to a good approximation of the field behavior, which is illustrated in Figure 3 for the local variation of the air gap flux density *B<sup>δ</sup>* compared to a linear T-FEM simulation.
