Search Results (13)

At present, most of the existing research on low-speed permanent magnet motors (LSPMMs) focuses on the surface-mounted type. There are few other rotor structures, and there is no comprehensive comparison of several widely used rotor structures. A comprehensive comparison of three different rotor structures for low-speed mining motors is carried out, including electromagnetic and loss characteristics, permanent magnet consumption, temperature distribution, etc. Firstly, three rotor structures of a 500 kW, 60 rpm low-speed motor are introduced, and the initial design parameters are determined. Secondly, the influence of each rotor design parameter on the electromagnetic characteristics is analyzed. Next, the electromagnetic optimization of the three rotor structures is carried out, and the motor performance of the three rotor structure optimization schemes is compared, including electromagnetic performance, permanent magnet consumption, motor temperature distribution, etc. Finally, in order to verify the correctness of the theoretical analysis, a prototype is made and tested based on the above analysis. The results show that for the electromagnetic characteristics, when the motors with three different rotor structures meet the performance requirements, the no-load line back-EMF of the inset surface-mounted motor is the lowest, but the back-EMF harmonic content of the inset surface-mounted motor is the highest. The copper loss of the spoke-type motor is the smallest, the efficiency is the highest, and the power factor is the lowest. In addition, the surface-mounted motor has the least consumption of permanent magnets and is more economical. Regarding the temperature distribution, when the same heat dissipation system is used, the temperature of the spoke-type motor with minimum copper loss is the lowest. Full article

Permanent magnet synchronous motors (PMSMs) are highly affected by magnetization, which determines the magnetization level in the permanent magnet (PM). There are three main magnetization methods: single-unit, stator coil, and post-assembly magnetization. Post-assembly magnetization is widely used in PMSM mass production due to its ability to achieve high magnetization performance using a separate magnetizing yoke. However, spoke-type PMSMs with ferrite PMs face challenges when using the post-assembly method. The structural configuration of two magnets located radially hampers effective magnetized field transmission to the rotor’s interior due to the narrow space between the magnets. Maximizing the magnetization rate becomes crucial, but the limited space in the spoke-type structure complicates this. This paper addresses the issue and analyzes factors influencing post-assembly magnetization characteristics. A novel yoke structure is proposed, reducing the distance between the coil and magnet, leading to more efficient magnetization. The parametric and performance comparative analysis shows an impressive 17.1%_p increase in magnetization rate with the proposed yoke structure compared to the existing yoke. This outcome contributed to a solution for enhancing the magnetization performance of spoke-type ferrite PMSMs. Full article

This study presents a structural analysis and optimization for the lightweight design of a buoyant rotor-type permanent magnet (BRPM) generator, which was first presented in Bang (2010), and compares its structural performance to that of a conventional generator with a spoke arm-type rotor and stator. The main benefit of a BRPM generator is that it can be constructed as a bearingless drive system, free from the mechanical failure of rotor bearings, by using a buoyant rotor. Additionally, the deformation of the generator by blade vibration can be effectively suppressed using joint couplings between the blades and the rotor. For design optimization, the objective is set as the mass of the rotor and the stator, and the maximum deformation of the airgap clearance between the rotor and the stator by external forces is constrained below 10% of the gap width. The commercial software OptiStruct is used for the analysis and optimization. In this investigation, the analysis and optimization are conducted for a 10 MW wind turbine generator. However, the proposed methods can be extended to larger generator designs without requiring considerable modification. The mass of the optimized 10 MW BRPM generator is 160.7 tons (19.3 tons for the rotor and 141.4 tons for the stator), while that of an optimized conventional spoke arm-type generator is 325.6 tons. Full article

The traditional radial flux PMSM and axial flux PMSM have an effective air gap on only one side, between the stator and rotor, and only the effective air gap generates electromagnetic torque. There are defects in the magnetic-field utilization, and it is difficult to improve the torque density. Therefore, this paper proposes an axial–radial-flux permanent-magnet synchronous motor (ARF-PMSM), which combines radial flux with axial flux, to be used in an elevator-traction machine-drive motor. The characteristics of the ARF-PMSM are that the stator core is made of a soft magnetic composite material and the winding is annular. The motor has three effective air gaps, which can achieve high torque density without increasing the overall dimensions. In this paper, the mechanical structure and operation mechanism of the ARF-PMSM are introduced, and the characteristics of its magnetic circuit structure are analyzed by using the equivalent magnetic circuit method. The torque characteristics and other electromagnetic characteristics of the ARF-PMSM, the traditional surface-mounted PMSM, and the spoke-type PMSM are compared and analyzed using the finite element method. The research results show that the proposed motor has high torque density, which provides a new design idea in the form of a high-torque-density PMSM for use in elevator-traction machines. Full article

This work studied the static magnetic pull of a modular spoke-type permanent magnet motor (MSTPMM) with no rotor eccentricity during the motor’s final assembly process and its dynamic magnetic pull during different motor operating states. A new final assembly scheme was proposed to significantly reduce the static magnetic pull during the final assembly process of the motor. The methods required to reduce the unbalanced radial magnetic pull of the whole stator, which is caused by partial stator module operation, were also studied. Firstly, the structure of the MSTPMM was examined. The static magnetic pull that occurred with the implementation of the two motor final assembly methods was studied in order to prove the effectiveness of reducing the maximum static magnetic pull. Moreover, the maximum magnetic pull during the assembly process was also observed. Then, the dynamic magnetic pull was studied with different motor operating states: no load, on load, and partial stator module operation. To solve the unbalanced radial magnetic pull of the whole stator, which is caused by partial stator module operation, methods of changing the angle between the stator current vector and the q axis (Ψ) or the d axis current (i_d) were also studied. Full article

Permanent magnet synchronous generators (PMSGs) with high output density per unit volume are becoming widespread in wind-power generation systems. Among them, spoke-type PMSGs are more challenging to magnetize than other PMSGs, owing to their structural characteristics. Magnetization performance is critical because it is directly related to the demagnetization and mass productivity of permanent magnets, and load performance is reduced when non-magnetization occurs due to the low magnetization performance. Additionally, the starting performance is crucial in wind turbines and is influenced by the cogging torque of the PMSG. This is because starting a wind turbine with a large cogging torque is more challenging. Therefore, this study proposes a spoke-type PMSG rotor shape design for low capacity wind turbines that considers magnetization and cogging torques. We analyzed the principle of magnetization and the factors influencing magnetization performance, and designed a rotor shape with improved magnetization performance. Additionally, we applied an asymmetric rotor barrier structure to reduce the cogging torque and analyze the performance of the final model using finite element analysis. We analyzed the temperature saturation during the operation of the final model using a thermal network method and validated the irreversible demagnetization accordingly. Full article

A novel asymmetric spoke-type interior permanent magnet (AS-IPM) machine is proposed in this paper. It utilizes the magnetic-field-shifting (MFS) effect to improve the torque performance, which achieves a high utilization ratio of both permanent magnet (PM) torque and reluctance torque. In addition, a general pattern of rotor topologies is proposed to represent all possible machine structures. Various rotor structures can be obtained by changing the design parameters of the general pattern. A non-dominated sorting genetic algorithm II (NSGA-II) is adopted to automatically search for optimal rotor configurations. With the aid of the optimization program, an asymmetric spoke-type rotor structure with improved performance is obtained. To showcase the advantages of the proposed machine, the electromagnetic performance is compared between a conventional spoke-type interior permanent magnet (S-IPM) machine and a proposed AS-IPM machine. The finite-element simulation results show that the optimal design of the AS-IPM performs a 7.7% higher output torque ripple due to the MFS effect while the total PM volume remains the same. Meanwhile, the torque ripple of the proposed structure is significantly reduced by 82.1%. Full article

This paper studies the optimal design and control scheme of a spoke-type interior permanent magnet motor (SIPM). An asymmetric rotor structure with flux barriers is designed to improve the torque density of SIPM. The design method improves the torque density by approximating the maximum value of the magnetic torque and the reluctance torque, wherein the torque components are separated by the frozen permeability method (FPM) to evaluate the contribution. This scheme does not increase the amount of permanent magnets or the motor size, and reduces motor weight while increasing motor torque output. Firstly, the asymmetric flux barriers are applied in a 27/4 SIPM to illustrate the design principle. Further, by optimizing the width of flux barriers, based on finite-element analyze (FEA), a higher torque density is obtained. Compared with the basic model, the output torque and the torque density of the optimal model are both increased. Based on the optimal model, an angle scanning method is proposed to orient the flux vector and dq-axis. Then, the mathematical model of the optimal model is established, and the maximum torque per ampere (MTPA) control system is designed. Compared with the conventional control system, the proposed control system has a higher torque per ampere (TPA), which shows that the designed control system can give full play to the advantages of the high torque density. Full article

This study describes the development of the world’s smallest interior permanent magnet synchronous motor (IPMSM) to increase the torque density of micromotors. The research evaluates the feasibility of the miniaturization of IPMSM since recent studies in this area focus on medium to large size compressor and traction motor applications. The standard-type and spoke-type IPMSM were selected for ease of micro machining. In order to surpass the performance of an inset motor of the same size used in previous research, the interior motors were designed with a different slot pole number, permanent magnet shape and rotor structure. Two types of interior motors were manufactured and tested to compare their performance. It was shown that the spoke-type interior motor had a better output torque, while the standard-type interior motor had a lower torque ripple, and both motors matched the specifications of commercially available motors. To achieve a higher torque density, the IPMSM designs increased the slot pole number from 6 slots 4 poles to 9 slots 6 poles. The torque density of the spoke-type motor was increased by 48% compared to the inset motor. The disadvantage is that the new design has a greater number of parts and smaller size, resulting in difficulties in manufacturing and assembly. Full article

Permanent magnet Vernier machine (PMVM) is a strong candidate for direct-drive applications in low-speed region because its power characteristic is higher than conventional permanent magnet machine (PMM). In this paper, the design of a dual-stator PMVM (DSPMVM) with spoke-type rotor is introduced. As a radial motor with dual-stator configuration, one on the outer and inner side, the rotor is equipped with support bars for practical and simple manufacturing, which is the aim of this study. The characteristics and performance of the proposed machine with and without the support bar are examined with finite element analysis (FEA). The DSPMVM and the support were manufactured and tested through experiments to verify proposed structure. Both simulation and experiment results show that there is little to no difference in performance when the support bar is equipped. Furthermore, the average deviation between simulation and experiment results is approximately 7% which is within the acceptable range. Full article

This study demonstrates that the use of a flared-shape rotor structure in interior permanent magnet (IPM) permanent magnet synchronous motor (PMSM) yields better performance than the basic IPM PMSM motor, using a spoke structure with ferrite magnets. To concentrate the effective magnetic flux, the proposed rotor structure is composed of a number of ferrite magnets, which are inserted in a flared shape in the rotor core. This paper shows the comparison with the analysis results of 2D finite element method (FEM), and it is shown that the proposed IPM PMSM motor can be an effective substitute for the basic IPM PMSM motor, which requires low torque ripple and high efficiency. In particular, the proposed flared IPM PMSM motor has lower pulsation of torque and superior efficiency, as well as lower acoustic noise and vibration, compared to the basic IPM PMSM motor. To verify the performance improvement of the proposed model, a prototype of the proposed model was manufactured. It was experimentally confirmed that the proposed model has lower torque ripple and higher efficiency than the basic model. Based on this performance improvement, the proposed flared IPM PMSM motor is suitable for electric vehicles and home appliances. Full article

This paper proposes a novel flux focusing magnetically geared (MG) machine for wind power generation, considering the permanent magnets (PMs) eddy current loss and the balance between the pull-out torque of MG machine and the back-electromotive force (EMF)of the PM brushless machine. The PM eddy current loss in the two rotors of the conventional surface-mounted MG machine is calculated and analyzed by using finite-element method. By adopting serial-spoke structure in the inner rotor, a novel rotor structure for a MG machine is proposed to reduce the PM eddy current loss. Moreover, in order to balance the pull-out torque and the back-EMF, several serial-spoke structures and the main design parameters are investigated. Then, a quantitative comparison between the proposed topology and the conventional surface-mounted MG machine is performed. The analysis results indicate that the PM eddy current loss of the proposed MG machine can be significantly reduced and its pull-out torque and back-EMF can be balanced well. Full article

The price of rare-earth metals used in neodymium-iron-boron (NdFeB) permanent magnets (PMs) has fluctuated greatly recently. Replacing the NdFeB PMs with more abundant ferrite PMs will avoid the cost insecurity and insecurity of supply. Ferrite PMs have lower performance than NdFeB PMs and for similar performance more PM material has to be used, requiring more support structure. Flux concentration is also necessary, for example, by a spoke-type rotor. In this paper the rotor of a 12 kW NdFeB PM generator was redesigned to use ferrite PMs, reusing the existing stator and experimental setup. Finite element simulations were used to calculate both electromagnetic and mechanical properties of the design. Focus was on mechanical design and feasibility of construction. The result was a design of a ferrite PM rotor to be used with the old stator with some small changes to the generator support structure. The new generator has the same output power at a slightly lower voltage level. It was concluded that it is possible to use the same stator with either a NdFeB PM rotor or a ferrite PM rotor. A ferrite PM generator might require a larger diameter than a NdFeB generator to generate the same voltage. Full article