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.