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The concentric magnetic gear is a transmission gear with a novel structure and a promising prospect,by using the magnetic field modulation principle,the large torque transmission is realized. On the basis of concentric magnetic gear structure,the modulation magnet ring is improved,the silicon steel is added on the inside of the modulation magnet ring to constitute a mechanical bridge. The model of the improved magnetic gear is simulated by using two dimensional（2D） finite element（FE） method,and the magnetic field and electromagnetic torque are calculated. At the same time,the magnetic field and torque are compared with the common gear. The results show that improved magnetic gear magnetic field is higher than normal- type magnetic gear,lower harmonic content,and torque is also improved. It is significant for the research and application of the concentric magnetic gear.

Spoke structure can increase the torque density of coaxial magnetic gear (CMG). However, the outer rotor can produce a large number of magnetic leakages. To improve the utility of PMs, a novel magnetic gear was proposed in this paper. The structure of the auxiliary flux modulator is a slotted iron yoke, and the slot angle is same as the stationary ring. Among, the permanent magnets (PMs) of inner rotor are adopted uneven block structure to improve air gap flux density. At the same time, the stationary ring adopts high-temperature superconducting (HTS) bulks, replacing the epoxy resin. In addition, Genetic algorithm (GA) is applied to calculate the optimal parameters of the proposed CMG. Finally, the air gap flux density and output torque of the magnetic gear a compared by the finite element method. The results show that the output torque of the proposed magnetic gear is effectively improved. [ABSTRACT FROM AUTHOR]

In this study, an analytical model is proposed to calculate the magnetic field and electromagnetic torque (including cogging torque) in the surface‐mounted permanent‐magnet (SMPM) machines with Halbach arrays accounting for semi‐closed slots. The analytical model can be used to calculate both no load and load air gap magnetic field of SMPM. The permanent magnets (PMs) on the rotor are arranged Halbach array and each pole is divided into four segments. Additionally, in order to improve the performance of the SMPM, the analytical model is combined with genetic algorithm to optimise some parameters of the motor. The analytical results from the proposed model have been compared with those issued from finite‐element method. Finally, the 12‐slot/8‐pole motor is manufactured and the back‐electromotive force, iron loss and load characteristics are validated by experiments. [ABSTRACT FROM AUTHOR]

This article proposes a novel hybrid-excited magnetic gear (HEMG) with eccentric magnet structure. The novel HEMG has a higher electromagnetic torque when compared to its conventional counterpart. This study looks into the magnetic field of coaxial magnetic gear during overload, and investigates the cause of demagnetization of permanent magnets (PMs) on rotor. The PMs are attached to the inner and outer rotor; PMs of inner rotor are eccentric structure and magnetized along the radial direction, PMs of outer rotor are the radial magnetized, and the outer rotor yoke is slotted and injected with current. The proposed HEMG topology with 4 inner and 23 outer pole pairs is established; the corresponding magnetic flux density distributions, electromagnetic torque, and torque ripples are assessed and verified by finite element analysis. Finally, the HEMG is built and tested; the test results show that its transmission efficiency is up to 92.6%, and the effective length of the prototype corresponds to the torque density that is 135.15 kN·m/m3. [ABSTRACT FROM AUTHOR]

In this paper, a novel flux switching permanent- magnet machine (FSPM) with consequent-pole magnets and flux bridges in the stator core is proposed to improve the torque capability of FSPMs with high pole ratios. The stator yoke and flux bridges adjacent to the magnets can provide magnetic paths for the main working harmonic field, thus the magnetic reluctance of the working harmonic field is reduced, and the flux modulation effect, winding back-electromotive force (EMF), and output torque of the proposed FSPM can be significantly improved compared to the regular FSPM with high pole ratios. The operation principles and stator–slot/rotor–slot combinations of the proposed FSPM are introduced. Then, the influences of pole ratio, split ratio, slot opening ratio, and PM width on the torque density of the proposed FSPM is investigated using finite element analysis. Moreover, after the investigations, a proposed FSPM is compared to a regular FSPM in terms of back-EMF, rated torque, power factor, etc. Finally, to verify the theoretical analysis, a 12-stator–slot/14-rotor–slot FSPM is built and tested. [ABSTRACT FROM AUTHOR]

This paper investigates a novel harmonic current injection method to optimize air-gap and yoke flux density distribution for multiphase motor simultaneously. The effect of harmonic currents on air-gap flux density and yoke flux density is analyzed as a whole, while the traditional method focuses on air-gap flux density optimization only. The proposed method fully makes use of multiple control freedoms and the optimal coefficients for corresponding harmonic current are derived. The theoretical analysis and experimental results indicate that novel harmonic current injection method is suitable for heavy load condition. Maintaining the same stator current density, a nine-phase induction motor improves torque density up to 8.47% with the proposed method. A three-phase induction motor is designed to verify the effectiveness of multiphase motor with concentrated full-pitched winding. Furthermore, the torque density and efficiency for two motors are compared under various load condition. Finally, a multiphase variable speed drive system is constructed and the proposed method is validated by experiments. [ABSTRACT FROM PUBLISHER]

Global optimization algorithms are widely used to effectively suppress the torque ripple in switched reluctance motors (SRMs). In this paper, an improved velocity-controllable particle swarm optimization algorithm (VCPSO) is proposed to optimize the turn-off angle of an SRM under the current chopping control (CCC) method. In addition, the performances of three global optimization algorithms are compared and analyzed. The specific steps are outlined as follows. First, the static non-linear inductance–current–position and torque–current–position curves of the SRM are obtained through finite-element calculations, and a non-linear model of the SRM is established on this basis. Second, the turn-off angle optimization method based on the VCPSO is proposed. Finally, the performances of the simulated annealing algorithm (SA), the genetic algorithm (GA), and the proposed algorithm are compared and analyzed in terms of torque ripple suppression. The obtained results show that the proposed VCPSO has the advantages of a low number of iterations, low torque ripple, and small peak current in the torque ripple reduction issue of the SRM. [ABSTRACT FROM AUTHOR]