Design and Analysis of Novel Wound Rotor Synchronous Machines with Saliency Ratio and Reluctance Torque Improvement

Abstract

In this thesis, the author focuses on the development of novel topologies of wound rotor synchronous machines (WRSMs) with enhanced reluctance torque utilization for high torque density and high efficiency. In particularly, two novel topologies are examined in detail from the view of simulations and experiments to demonstrate the effectiveness.

Firstly, based on the background that reluctance torque is expected to alleviate the shortcomings of the NdFeB and the problems of copper loss, the salient pole WRSMs that generally have low saliency ratio, are redesigned with novel topologies. The design procedure including the design concept, operating principle and research method for the novel topologies are discussed in detail.

Secondly, the WRSM with single air barrier is first proposed due to the low permeability of the air. The optimal single air barrier in the q-axis flux loop reduces the q-axis inductance to improve the saliency ratio of the WRSM. Then, the ferrite magnet with the similar permeability to the air is assisted with the opposite magnetization direction in the q-axis flux loop for high saliency ratio and the torque-angle approaching. All the investigated machines in this thesis share one stator and only rotors are different. In particular, two proposed WRSMs have been optimized for high performance, in which the Latin hypercube sampling (LHS) method is applied in a design of experiments process to select the sampling points, and the Kriging method is performed for approximation modeling, while a genetic algorithm (GA) is carried out for obtaining the optimal points for the design variables.

Finally, two optimized WRSMs are developed and analyzed by FEM. Through a comparison with each corresponding conventional WRSM, the first proposed machine with single air barrier can achieve higher reluctance torque by enhanced saliency ratio and the second proposed machine with assist ferrite magnet exhibit higher saliency ratio as well as the torque-angle approaching. The prototypes of the two optimized WRSMs are manufactured. Then the experiments are carried out to verify the design and simulation results.