Radial electromagnetic force and vibration in synchronous reluctance motors with asymmetric rotor structures

Abstract

Asymmetrical rotor topologies were previously proposed for synchronous reluctance motors (SynRM) to reduce the torque ripple. However, potential negative effect of these topologies on mechanical vibration, which is often serious in SynRM, was hardly studied and such an effect is investigated here. An analytical model is established, through which the spatial orders of the radial electromagnetic force with various rotor topologies are derived, and the relationship of the peak frequencies and the corresponding spatial orders in the radial electromagnetic force is revealed. It is shown that some asymmetric rotor topologies will reduce the order of the lowest spatial harmonic for the radial electromagnetic force, and consequently increase the vibration. Finite element analysis and experiments demonstrate the same results. Finally, a specific rotor topology with asymmetry about both d-axis and q-axis is recommended, which can reduce the torque ripple, but would not deteriorate the radial electromagnetic force and vibration.This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

Power train degradation modelling for multi-objective active power control of wind farms

“…The F el in this diagram represents the radial electromagnetic force in the air-gap surface area of the PMSG. The PMSG radial electromagnetic force is due to the interactions within or between armature reaction and permanent magnet fields including the stator slotting effect which is a function of tempo-spatial variations of B ı−r as the radial component of air-gap magnetic flux density described by [7,24]…”

Square-wave drive for synchronous reluctance machine and its torque ripple analysis

“…Two iron bridges are designed in the inner center flux barrier to ensure the mechanical stress at maximum speed operation. This machine has been optimized for maximum torque density and minimum torque ripple with sinusoidal-wave drive in [19], where the torque ripple is defined as the ratio of peak-peak torque to average torque in this paper.…”

“…The other is the interaction between the armature current fundamental with the higher order harmonics in the phase inductances, e.g., 4 th , 6 th and 8 th . The high order harmonics in the phase inductance can be reduced with the various design techniques, which is generally adopted in the torque ripple mitigation of SynRM with sine-wave drive [12]- [19]. For the investigated SynRM, the harmonics in the phase inductance are inherently small after parametric optimization, and the torque ripple is negligible with sine-wave current.…”

“…It has been widely investigated that the torque ripple in the SynRM is large if not designed properly [11]. Some design techniques have been conducted to mitigate the fluctuating torque for the SynRM to obtain smooth operation in [12]- [19]. In [12] and [13], the rotor flux barrier is regarded as slots in rotor, and the combination of stator slots per pole pair and rotor slots per pole pair is optimized to achieve low torque ripple.…”

“…Moreover, a 'Machaon' rotor is proposed in [15] by employing different flux barrier end angles for adjacent flux barriers, and a rotor composed of 'Romeo' part and 'Juliet' part is proposed in [16] to compensate the torque pulsating components. Besides, a rotor structure with asymmetric flux barrier is presented in [17] [18] [19], for example, by shifting the center line of each flux barrier at a stator slot pitch to compensate the torque ripple caused by the stator slot harmonics. To avoid the unbalance of rotor structure, [18] proposes an asymmetric flux barrier rotor structure by shifting Square-Wave Drive for Synchronous Reluctance Machine and its Torque Ripple Analysis Jian-Xin Shen, Shun Cai, Dong-Min Miao, Dan Shi, Jacek Gieras, and Yun-Chong Wang S the flux barrier end merely.…”