A simple and general approach to determination of self and mutual inductances for AC machines

Modelling of AC electrical machines plays an important role in electrical engineering education related to electrical machine design and control. One of the fundamental requirements in AC machine modelling is to derive the self and mutual inductances, which could be position dependant. Theories developed so far for inductance determination are often associated with complicated machine magnetic field analysis, which exhibits a difficulty for most students. This paper describes a simple and general approach to the determination of self and mutual inductances of different types of AC machines. A new vector projection method is proposed. In this method, integration of the magnetic field may simply be replaced by vector projection of the field vector. Inductance may then be obtained by observing the magnetic field axes and the phase winding axes. Examples of applying the proposed method for inductance determination are given for a 3-phase, salient-pole synchronous machine, and an induction machine.