Torque Analysis of Permanent-Magnet Flux Switching Machines With Rotor Step Skewing

Linear flux-switching permanent magnetic (LFSPM) machines are good choices for long stroke applications. These machines deliver high thrust force density in addition to the machine structure where permanent magnetics (PMs) and windings are all on the short mover. For LFSPM machines, their performance is always affected by big thrust force ripple. In this paper, for two C-core LFSPM machines of high thrust force capability, including a 6/13 C-core LFSPM (6/13LFSPM-C) machine and a sandwiched C-core LFSPM (SLFSPM-C) machine, and a thrust force ripple reduction method is proposed. The proposed method is developed by reducing the slot effect component of the cogging force based on staggered stator tooth, and suppressing the thrust force ripple caused by unbalanced three phase back-electromagnetic forces (EMFs) based on two end PMs. Based on finite element analysis (FEA) results, both C-core LFSPM machines can achieve small thrust force ripples as well as high sinusoidal back-EMFs, and at the same time, maintain high thrust force capability with the proposed method. It was also found that, the improved SLFSPM-C machine exhibited the same thrust force capability as the improved 6/13LFSPM-C machine, but with a much smaller thrust force ripple.

Section: Step 1 Reduction Of the Cogging Force And Suppression Of Thmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Thrust Force Ripple Reduction of Two C-Core Linear Flux-Switching Permanent Magnet Machines of High Thrust Force Capability

Hao

Wang

2017

“…Detent force of the flux-switching linear motor is greatly reduced by using the skewing technology [26]. Torque ripple of 12/10 stator/rotor pole and 12/14 stator/rotor pole flux-switching machine topology is effectively reduced based on the rotor step skewing [27]. However, the period ratio of cogging torque to the back EMF is ě3 in [26,27].…”

Section: Introductionmentioning

confidence: 99%

“…Torque ripple of 12/10 stator/rotor pole and 12/14 stator/rotor pole fluxswitching machine topology is effectively reduced based on the rotor step skewing [27]. However, the period ratio of cogging torque to the back EMF is ≥3 in [26,27]. This paper mainly researches torque ripple reduction for modular motor and arc-linear motor, especially for that period ratio of cogging torque to the back EMF equals one.…”

Section: Introductionmentioning

confidence: 99%

Torque Ripple Reduction of a Novel Modular Arc-Linear Flux-Switching Permanent-Magnet Motor with Rotor Step Skewing

Liu

Zhao

2016

Abstract:A novel modular arc-linear flux-switching permanent-magnet motor (MAL-FSPM) used for scanning system instead of reduction gearboxes and kinematic mechanisms is proposed and researched in this paper by the finite element method (FEM). The MAL-FSPM combines characteristics of flux-switching permanent-magnet motor and linear motor and can realize the direct driving and limited angular movement. Structure and operation principle of the MAL-FSPM are analyzed. Cogging torque model of the MAL-FSPM is established. The characteristics of cogging torque and torque ripple are investigated for: (1) distance (d end ) between left end of rotor and left end of stator is more than two rotor tooth pitch (τ p ); and (2) d end is less than two rotor tooth pitch. Cogging torque is an important component of torque ripple and the period ratio of the cogging torque to the back electromotive force (EMF) equals one for the MAL-FSPM before optimization. In order to reduce the torque ripple as much as possible and affect the back EMF as little as possible, influence of period ratio of cogging torque to back EMF on rotor step skewing is investigated. Rotor tooth width and stator slot open width are optimized to increase the period ratio of cogging torque to back EMF. After the optimization, torque ripple is decreased by 79.8% for d end > τ p and torque ripple is decreased by 49.7% for d end < τ p . Finally, 3D FEM model is established to verify the 2D results.Keywords: modular arc-linear flux-switching permanent-magnet motor (MAL-FSPM); cogging torque; torque ripple; harmonics; period ratio of cogging torque to back electromotive force (EMF); rotor step skewing; finite element method (FEM)

“…Optimizing the rotor structure is however a favorable method for FSPM machines. Rotors with stepped skew were adopted in [22,23] to reduce the cogging torque and torque ripple under various load conditions. Various kinds of notching schemes and their influence on cogging torque are evaluated in [24,25].…”

Section: Introductionmentioning

confidence: 99%

Influence of Different Rotor Teeth Shapes on the Performance of Flux Switching Permanent Magnet Machines Used for Electric Vehicles

Zhao

Yan

et al. 2014

This paper investigated a 12-slot/11-pole flux switching permanent magnet (FSPM) machine used for electric vehicles (EVs). Five novel rotor teeth shapes are proposed and researched to reduce the cogging torque and torque ripple of the FSPM machine. These rotor teeth shapes are notched teeth, stepped teeth, eccentric teeth, combination of notched and stepped teeth, and combination of notched and eccentric teeth. They are applied on the rotor and optimized, respectively. The influences of different rotor teeth shapes on cogging torque, torque ripple and electromagnetic torque are analyzed by the 2-D finite-element method (FEM). Then, the performance of FSPMs with different rotor teeth shapes are compared and evaluated comprehensively from the points of view of cogging torque, torque ripple, electromagnetic torque, flux linkage, back electromotive force (EMF), and so on. The results show that the presented rotor teeth shapes, especially the combination of stepped and notched teeth, can greatly reduce the cogging torque and torque ripple with only slight changes in the average electromagnetic torque.