Inductance Coefficients of Three-Phase Inductor Alternators: Part I - Analytical Study

The paper develops expressions for various inductance coefficients of three-phase inductor alternators on the basis of a harmonic permeance distribution in the air gap. These expressions involve harmonics in the MMF distribution of the armature windings and also harmonics in the permeance distribution due to the non- uniform air gap. The analysis shows that, when the armature carries current, both odd and even harmonic voltages are induced in it. However, a certain group of harmonics can be eliminated by suitably choosing the number of rotor teeth and stator teeth and number of coils per phase. It is also shown in the analysis that inductor alternators having an odd number of rotor teeth are superior to those with an even number of rotor teeth. Performance equations of both types of alternators are also established.