*2.2. Harmonic Wave Model*

The operating behavior, in particular the electromagnetic torque, the electromagnetic forces, and the ohmic and iron losses of an IM is significantly influenced by the orders and amplitudes of the harmonics that occur. These harmonics cannot be modeled in the FWM. Therefore, the HWM considering the multiple armature reaction provides a possibility for the analytical description of these effects [4–6]. Assuming a sinusoidal stator current, the discrete distribution of the stator windings, neglecting the slot openings, results in non-sinusoidal stator Magnetomotive Force (MMF) in the form of a staircase function. The currents of different order and amplitude induced in the rotor by this stator field, in turn, each generate staircase-shaped rotor MMF, which in turn induces new voltages in the stator (*primary armature reaction*). The harmonic model according to [4–6] additionally considers the secondary, tertiary, and quaternary armature reaction [9]. In addition to the multiple armature reaction, further effects causing harmonics, such as stator and rotor slotting or rotor eccentricity, can be considered. Due to the assumption of an infinitely high iron permeability (*μ*Fe → ∞) saturation harmonics cannot be represented in this HWM. Further important physical quantities and effects affecting the value range or the level of detail of the machine modeled with the HWM are briefly explained.
