Comparison of flux control capability of a series double excitation machine and a parallel double excitation machine

This paper presents a comparison of open circuit flux control capability of two structures of double excitation synchronous machines. First, the structures of these two machines are presented: one is a series double excitation machine and the other one is a parallel double excitation machine. The flux control capability of the parallel double excitation machine is evaluated experimentally using a build prototype. For the study of flux control capability of the series double excitation machine, a 2D exact analytical solution of open circuit magnetic field distribution in a idealized geometry of a series double excitation synchronous machine is established. It involves solution of Maxwell´s equations in stator slots, airgap, PM´s region and rotor slots. The validity of developed model is demonstrated via comparison to finite element analyses. Then, developed model is used to study the open circuit flux control of a series double excitation machine having same overall dimensions as the parallel double excitation machine prototype. Finally, open circuit flux control capabilities of both structures are compared.