Radially Laminated Magnetic Barrier Rotor Doubly Excited Brushless Machine

Doubly-Excited Brushless Machine with Radially Laminated Magnetic-Barrier Rotor (RLMB-rotor DEBM) is a novel AC machine. It has two sets of separate windings with different pole numbers located on the stator, and the rotor is structured without slip rings and brushes but with several reluctance segments with pole number different from either of the stator windings. It appears very attractive for its rugged structure, good compatibility with power converter, and flexible operational modes for various applications of variable-speed constant-frequency generating and adjustable speed drive systems. It is potential to achieve high efficiency, low cost, enhanced reliability and flexible control for variable-speed drive and variable-speed constant-frequency generating systems.The work of this dissertation focuses mainly on the RLMB-rotor DEBM.Firstly, by applying the winding function theory, the linear magnetic flux model of the RLMB-rotor DEBM is established to reveal the principles of electromagnetic energy conversion of this machine, calculate the air-gap flux density distribution and winding flux linkages of the two sets of stator windings. Then, the self and mutual inductance of the two stator windings is computed for equivalent circuit derivation. Based on the linear model, self inductance characteristic, mutual inductance characteristic and torque capabilities are investigated with three different rotor pole numbers and three different rotor structures. The results from this approach are used to highlight the common principles of electromechanical energy conversion for the RLMB-rotor DEBM with unconventional magnetic structures and different rotor pole numbers and different rotor structures.Secondly, by using finite element method, the transient nonlinear model of the RLMB-rotor DEBM is developed. With a set of given excitation currents imposed on the transient nonlinear model, the magnetic fields are calculated directly for the complicated lamination geometries, the actual dual-winding connections, and the nonlinear magnetic materials. Various flux patterns throughout the cross-section of the machine are plotted for various cases at different rotor positions. In addition, the winding self and mutual flux linkages are calculated and plotted as a function of the rotor positions. Subsequently, the load conditions are simulated and the torque capability is evaluated in the voltage excitation mode. As the last step, the internal magnetic field analysis is translated into the terminal characteristics of RLMB-rotor DEBM. It is hoped that the analysis presented in this paper provides insights into the optimal design and control of RLMB-rotor DEBM in practical applications.Thirdly, by analyzing the electromagnetic linkage of two sets of stator windings with rotor magnetic coupling, the transient model and dynamic equivalent circuit are investigated. In this approach, the principles of winding turns converter, frequency converter and pole converter are investigated to reveal that the equivalent circuit for this machine is similar to that of a wound rotor induction machine.Fourthly, a sample machine of RLMB-rotor DEBM is designed and built. The operation performances for various operation modes of the sample machine are investigated experimentally. The experimental results and the simulation results are compared and analyzed.Finally, by using finite element analysis model of the RLMB-rotor DEBM, the megawatt level machines with inner-rotor and outer-rotor are designed to investigate the applications in wind generating system.