Torque ripple reduction of synchronous reluctance machines

Abstract

Purpose – The purpose of this paper is to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of synchronous reluctance machine with emphasis on output torque capability and torque ripple. Design/methodology/approach – AC synchronous reluctance machine (SynRM) or permanent magnet assisted SynRM presently receives a great deal of interest, since there is less or even no rare-earth permanent magnet in the rotor. Most of SynRM machines employ a stator that is originally designed for a standard squirrel cage induction motor for a similar output rating and application, or the SynRM machine with 24-slot, four-pole are often directly chosen for investigation in most of the available literature. Therefore, it is necessary to investigate the influence of stator and rotor pole number combinations together with the flux-barrier layers number on the performance of SynRM machine with emphasis on output torque capability and torque ripple. Findings – The average torque decreases with the increase of the pole numbers but remain almost constant when employing different stator slot numbers but with the same pole number. In addition, the torque ripple decreases significantly with the increase of the stator slot number. The machine with double-layer flux-barrier in the rotor has the biggest average torque, while the machines with three- and four-layer flux-barrier in the rotor have almost the same average torque but their value is slightly smaller than that of machine with double-layer flux-barrier. However, the machine with three-layer flux-barrier has the lowest torque ripple but the highest torque ripple exists in the machine with double-layer flux-barrier. Research limitations/implications – The purely sinusoidal currents are applied in this analysis and the effects of harmonics in the current on torque ripple are not considered in this application. Originality/value – This paper has analyzed the torque ripple and average torque of SynRMs with considering slot/pole number combinations together with the flux-barrier number.

Simple Design Approach for Low Torque Ripple and High Output Torque Synchronous Reluctance Motors

“…(a) the number of stator slots should be maximized as much as possible; (b) the number of rotor layers can be selected based on [14] or the following Table 1 given in [22,23]. Then, to choose the flux-barriers angles, we propose an angle β (see Figure 2) and use it to control the rotor slot pitch angle γ.…”

“…Eventually, the positive and negative torque pulsations may cancel each other, resulting in a reduced torque ripple for the SynRM. Based on [14,22,23], we can propose a new approach that can produce a preliminary SynRM design with low torque ripple and better average torque by considering the following steps:…”

Effect of Geometrical Parameters on Optimal Design of Synchronous Reluctance Motor

“…1 includes Heights of the barriers (h b1 , h b2 , h b3 ), Length of the barriers (l b1 , l b2 , l b3 ), Angular positions at airgap, (∆δ 1 , ∆δ 2 , ∆δ 3 ) defined with respect to centre of the shaft, Flux barrier tip angles (β 1 , β 2 , β 3 ) measured between the ends of the flux barriers, defined with respect to centre of the shaft, Iron rib thickness(t i ), the thickness between the end of the flux barriers and periphery of the rotor and Air gap length (a g ). The lamination of the prototype rotor used for analysis is based on significant contributions made in [3,12,26], and is shown in Fig. 2.…”

“…The flux barrier tip angles [11,12] (β 1 , β 2 , β 3 ), describes the extent bounded by the flux barrier ends in degrees. .…”

“…The parameters comprises of height of the barriers [3,[5][6][7][8][9][10], length of the barriers [5,10], angular positions at air gap [3,[5][6][7][8][9], barrier tip angle [11,12] and iron rib thickness [3,13]. Besides the above mentioned parameters, the effect of airgap and effect of skewing [3,12] of rotor is analysed.…”