Electrically- and hybrid-excited synchronous motors (EESMs/HESMs) are increasingly being favored over permanent magnet alternating current (PMAC) motors for high-performance applications due to their superior field weakening capacity, enhanced overload capacity, and reduced reliance on permanent magnets (PMs). However, EESMs/HESMs require controlled electrical excitation for their field winding in the rotor. Traditional brush and slip ring-based excitation methods are inefficient, require frequent maintenance, and suffer from reliability issues, including wear and tear. Although existing brushless excitation systems (BESs) incorporate auxiliary machines or modify motor designs to eliminate brushes and slip rings, most rely on controlled switches placed in the rotor to reverse the polarity of the field current, necessitating complex wireless communication between the stator and rotor. To address these challenges, this study introduces a novel BES for EESMs/HESMs. The proposed system can control bipolar field current (BFC) entirely from the stator without any rotor-side controllers or wireless communication. First, the operating principle of the proposed BES, which comprises a stationary-side series resonant converter (SRC) in conjunction with a rotary transformer (RT) having stator-side primary, and two rotor-side secondary windings, is explained. Secondly, a selective multiple excitation frequency control method is presented, which utilizes selectively tuned resonant tanks in each of the secondary windings to achieve bipolar field current control entirely from the stator. This approach obviates the need for any communication between the stator and the rotor. Finally, the performance of the proposed system for a 105 kW, 6000 rpm segmented-rotor HESM is evaluated using a co-simulation framework in which the RT and HESM are modeled in ANSYS Maxwell, whereas the BFC converter is modeled in the MATLAB/Simulink and ANSYS Twin Builder. The proposed method also helps enhance the torque density of HESMs.
Dey et al. (Thu,) studied this question.