On the Comparison Between the Stator- and Rotor-excited Claw Pole Alternators

Abstract

This article compares the electromagnetic features of rotor-excited claw pole alternators and stator-excited claw pole alternators, which share the same rotor active length. Accounting for the 3D flux path characterizing both machines, the comparison study is based on a 3D finite-element analysis. Following a description of the flux linkage in these machines, special attention is paid to the investigation of their magnetic features, including the air gap spatial repartition of the flux density, torque-angle characteristics, and no-load characteristics. It has been found that the rotor-excited claw pole alternator exhibits a higher back-electromotive force production capability than the stator-excited claw pole alternator, which is penalized by (i) the additional lateral air gaps located in between the collectors and the magnetic rings, and (ii) the homopolar flux. The torque production capability of the stator-excited claw pole alternator is also affected by these drawbacks at low values of the field current. Increasing this leads to a saturation of the rotor-excited claw pole alternator, whose torque production is similar to that of the stator-excited claw pole alternator.