Development of Design Techniques to optimize the performance of Synchronous Reluctance Machines with Anisotropic Rotor Structure.

Abstract

This thesis provides a comprehensive understanding of Synchronous Reluctance Machines (SynRM), addressing both the fundamental principles of operation and the development of various design techniques. To expedite the sizing stage, a precise analytical model was developed which combines two methods: to calculate the air-gap flux density and average torque, the magnetic potential of the rotor and stator were used, and the torque ripple was calculated using the energy stored in the air-gap. This model is extended to machines with multiple flux barriers. Comparisons with the Finite Element Analysis (FEA) yield promising results, both in terms of air-gap flux density and electromagnetic torque. However, a harmonic analysis reveals that the analytical model tends to overestimate the air-gap flux density and torque due to underlying assumptions made during its development. Despite this, the model offers valuable capabilities, including the ability to extract machine parameters in the d-q reference frame, facilitating a preliminary control strategy analysis. In pursuit of further enhancing SynRM performance, an asymmetric rotor topology was Introduced. This feature achieves a significant reduction in torque ripple and an increase in maximum internal power factor. While both designs exhibit similar efficiency, the asymmetric design excels by offering a wider constant power speed range (CPSR). Simultaneously, a comprehensive study on discrete skew methodology was conducted. The proposed method provides deeper understandings into the impact of skew angle on torque ripple. This method introduces an indicator to assess the potential reduction achievable by selecting various skew steps and angles. Validation through FEA in both two and three dimensions reinforces its applicability. These techniques were used to design two SynRMs using the same stator with two different rotor topologies, one symmetrical and the other asymmetrical. The design was carried out by optimization using a multi-objective genetic algorithm (MOGA), coupled with the techniques developed throughout the thesis. The preliminary results highlight the superiority of the asymmetric design in terms of performance indices. However, it is worth noting a significant reduction in these indices when skew is applied, underscoring the importance of design choices. These two rotor topologies were manufactured to validate the improvement through experimental measurements.