Modelling of saturated AC machines including air gap flux harmonic components

A new saturation model for induction machines is presented which can be easily extended to other types of AC machines. It is shown that saturation is responsible for the generation of flux space harmonic components traveling in the air gap with the same synchronous speed as the fundamental flux component with the third being the dominant harmonic component. Superposition of the effects of the fundamental and third-harmonic components of the air gap flux is utilized in order to model the saturation of the ferromagnetic parts of the machine. The concept of winding functions is used to derive the inductance terms relating both stator and rotor winding components. In this approach the air gap length is assumed to be variable, being a function of the position and level of the air gap flux. Terminal and torque values for steady and transient states are obtainable from the proposed model, with experimental results showing that the model predicts spatial saturation effects with good accuracy.<>