Design optimization and performance improvement of synchronous reluctance machines
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Date
2019-06-13
Authors
Hunuhene Gedara, Indula Prasad Abeyrathne
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Abstract
The performance capability of a four pole Synchronous Reluctance Machine (SynRM) is improved using an optimized coordinate based four flux barrier hyperbolic rotor structure. Firstly, a study is conducted to compare and improve the operating performance of 36 slot four-pole SynRMs optimally designed based on three distinct Objective Functions (OFs) for (i) torque ripple minimization (RM), (ii) saliency ratio maximization (SM), and (iii) combined objective function (COF) optimization to simultaneously minimize the torque ripple and maximize the saliency ratio while supporting the required torque. For the optimized SynRMs, a normal round rotor and a rotor with a cut-off are used in the Finite Element (FE)-based rotor design optimization, while the stators are identically designed using classical electric and magnetic loading principles. The SynRMs’ dimensions and efficiencies are based on IEC-90S frame size limitations and IE3 efficiency standards, respectively. Secondly, two additional SynRMs with 24 slots and 48 slots are considered with normal and cut-off rotors. Four new SynRMs are optimized using appropriate COFs to minimize the torque ripple and maximize the saliency ratio of the machines while also supporting the desired developed torque. Performance of each optimized SynRM is compared to introduce a final design. Finally to further improve performance capabilities such as developed torque, power factor and wide speed range, addition of low-cost ferrite magnet is considered along q-axis. A different COF is used to maximize the developed torque and reduce torque ripple simultaneously for the design optimization of PM assisted SynRMs (PMaSynRMs). A comparative electromagnetic study and mechanical stress and deformation analysis are carried out to predict the performance capabilities and operating limits of the designed SynRM and PMaSynRMs. The optimally designed SynRM and PMaSynRM are fabricated and tested to verify the theoretical expectations.
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Keywords
Design optimization, Synchronous reluctance machine, SynRM, Finite element analysis, Permanent magnet assisted synchronous reluctance machine, Rotor design