Design of synchronous reluctance machines with a wide speed range

Yılmaz, Yusuf Basri
Synchronous reluctance machines (SynRMs) are a good alternative for traction and industrial applications due to their good power density, low cost and high efficiency. However, they suffer from high torque ripple, low power factor and poor high speed performance due to their singly excited nature. To overcome these challenges, rotor geometries are optimized to get a low torque ripple and ferrite magnets are inserted in the flux barriers to get a higher power factor and a better high speed performance. This thesis aims to propose a methodology to design synchronous reluctance machine with a wide speed range with high power output by using parametric sweep and optimization methods. It is observed that rotor design has an effect on the high-speed performance of SynRMs. However, even the maximum power of the optimized machine decreases sharply as the field weakening region of the machine is extended. Moreover, when the high speed performance of a SynRM is concerned, mechanical and electromagnetic designs must be performed concurrently. To assure a mechanically robust rotor structure, radial ribs must be added to the flux barriers but these connections cause a decrease in the electromagnetic performance of the machine. So, the high speed performance of the machine decreases further as the ribs in the flux barriers must get thicker as the maximum speed is increased. Based on these findings, it is concluded that PM assistance is required to reach an acceptable high speed performance. Therefore, the amount of required PM material to reach a satisfactory output power at the maximum speed is determined for selected SynRM designs. These analysis is performed with both ferrite and NdFeB type permanent magnet materials, and ferrite assisted SynRM design is found to be favorable due to its much lower cost. Finally, the design and analysis methods are validated with the measurements taken from a small-scaled prototype SynRM that is designed in this study.


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Citation Formats
Y. B. Yılmaz, “Design of synchronous reluctance machines with a wide speed range,” M.S. - Master of Science, Middle East Technical University, 2021.