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This article proposes a new “switched lumped reluctance network”-based equivalent circuit for a switched reluctance motor (SRM) under saturation. The proposed circuit incorporates the effects of the position-dependent switching of the phase windings and changing position of the rotor with respect to the stator. This feature enables the analysis of non-uniform and dynamic variation of flux in motor iron sections along with that in the air gap and their effects on the phase current. The proposed model, thus, emulates the operation of an SRM, more truly, through an equivalent circuit approach. The accuracy of the proposed model is verified by comparing the analytical results of five different stator–rotor sets (having different air gaps and tooth angular widths) with the finite-element method (FEM) simulated results and found to be in excellent mutual agreement. The static and dynamic performance obtained using the proposed model has been validated by experiments on a four-phase, 1-kW, 300-V, 1000-rpm SRM. [ABSTRACT FROM AUTHOR]

With the emergence of electric vehicles and electric aircraft technologies, lightweight motors have become a requirement. Conventional motors are generally made up of coils, permanent magnets, heavy iron stators, and rotor cores. This article presents complete analytical modeling and design of a novel coreless multi-phase magnetic resonant motor (MMRM), conceptualized through the approach of magnetic resonance coupling. The removal of magnetic iron cores drastically reduces the weight of the resulting motor. The stator and rotor cores of the motor are made of reinforced plastic fibers and can be 3-D printed. Unrelated to the general operating principle of the existing conventional electric motors, resonant wireless power transfer (WPT) is the key feature of these motors. All the essential machine characteristics, such as self-inductance, mutual inductance, torque, and frequency domains, are fully developed. The mathematical modeling of the machine’s physical phenomena is linked to its operation by simulation. This article shows the design concept and discusses the simulation procedure used to verify the developed analytical model through a finite-element analysis (FEA) from the established modeling topology equivalent to the proposed configuration motor model. Although the design is straightforward, an accurate analytical modeling and analysis are significant challenges to consider. [ABSTRACT FROM AUTHOR]

There are applications like electric-power-assisted steering system in which strict requirements on the cogging torque of the machine should be fulfilled. Numerous techniques and methods are introduced to minimize the inherent cogging torque of the machine, but manufacturing tolerances and imperfections still can cause extra cogging torque. In this article, the impact of punching on the manufacturing-induced cogging torque of segmented permanent-magnet synchronous machines is investigated. The punching model is implemented by modifying the BH curve of the steel as a function of distance from the cut edges. The parameters of the new BH curve are identified by means of standard Epstein frame measurements using steel strips with different widths. Then, the punching model is incorporated into the finite element (FE) model of a 10-pole 12-tooth segmented stator machine designed for power steering application. It is observed that deviation among the magnetic properties of the teeth caused by punching can introduce extra low-order harmonics in the cogging torque of the machine. The amplitude of the new orders can be comparable or even much bigger than the inherent orders, where not only the magnitude of deviation but also the arrangement of teeth with given punching parameters play a role. [ABSTRACT FROM AUTHOR]

A model order reduction (MOR) method for an induction motor using a Cauer ladder network (CLN) is developed in the frequency domain. A multiport frequency transformation between the stator and mover domains is derived by neglecting the spatial harmonic interactions. Even after neglecting the harmonic interactions, the reduced model provides a reasonably accurate frequency response, which is more accurate than that of the conventional approximated equivalent circuit. [ABSTRACT FROM AUTHOR]

In this work, isogeometric mortaring is used for the simulation of a six-pole permanent magnet synchronous machine. Isogeometric mortaring is especially well suited for the efficient computation of rotating electric machines, as it allows for an exact geometry representation for arbitrary rotation angles without the need for remeshing. The appropriate B-spline spaces needed for the solution of Maxwell’s equations and the corresponding mortar spaces are introduced. Unlike classical finite-element methods (FEMs), their construction is straightforward in the isogeometric case. The torque in the machine is computed using two different methods, that is, Arkkio’s method and using the Lagrange multipliers from the mortaring. [ABSTRACT FROM AUTHOR]

In current engineering, the skewing slots approach is commonly used for permanent magnet synchronous motor (PMSM) to reduce torque ripple and electromagnetic vibration. However, this approach may limit the axial length of the motor and increase the manufacturing cost. This article studies a segmented rotor with different pole widths approach to mitigate torque ripple and electromagnetic vibration for PMSM, which has a lower implementation cost and facilitates mechanized production. The mapping relationship between geometric dimensions and torque performance is obtained, and the optimal dimensions are determined. An 8-pole/48-slot V-shaped PMSM is taken as the original motor, and the influence of engineering error on the torque performance of the presented approach is discussed. The electromagnetic performances and vibration responses of the motor with the presented approach are compared with that of the skewing slot motor to verify the effectiveness of the presented approach. Finally, prototypes are built, and intensive experimental tests are carried out to verify the analysis and comparison. [ABSTRACT FROM AUTHOR]

The tubular linear oscillating machine can achieve reciprocating movement directly without auxiliary transmission mechanisms, which is widely used in the free-piston energy conversion system. To achieve a lower thrust ripple and eliminate the eddy current effect, a circumferential silicon steel stack is usually utilized in the stator, however, it results in assembling difficulties. In this article, a radially split lamination tubular linear permanent magnet oscillating machine with auxiliary configuration (RSL-TLPMOMA) is proposed to solve the problem. First, the laminated coefficient expression of split-laminated is deduced, the influence of laminated number and radius ratio on laminated coefficient is discussed, and the optimal combination of the laminated number under different radius ratios is given. Second, the subdomain (SD) method is used to analyze RSL-TLPMOMA, the auxiliary teeth, slot, and end effect are considered. Finally, a prototype is manufactured and tested. [ABSTRACT FROM AUTHOR]

This article presents a 3-D hybrid analytical prediction model for an air-cored linear-rotary induction machine (LRIM) in which its columnar movable armature surfaced with the conductor. The analytical magnetic distributions in the conductor and air gap of the LRIM are predicted by employing a group of H-formulations in the conductor and the Laplacian equations with magnetic scalar potential (MSP) in the others in the Cartesian coordinate. The correctness of the magnetic field distributions and the eddy-current distributions is verified by the numerical computational results using the 3-D finite-element method (FEM). [ABSTRACT FROM AUTHOR]

This article proposes a hybrid analytical modeling procedure for the performance parameter estimation of synchronous reluctance machine, including its operation in the region of magnetic saturation. The proposed model better estimated the torque profile through improved translation and stepped transition of rotor flux barriers. The non-linear operation is simulated by considering the global saturation and estimating the machine’s operating point on the magnetization curve of the core material. The procedure formulation focuses on improving the accuracy and rapidness of the iterative design process. The obtained results are validated against an already established design analysis technique, finite-element analysis, and the frequency spectrum analysis of practical machine results. With the improved accuracy and the least requirement of simulation runtime and computational resources, the modeling procedure can be utilized as an initial design iteration tool. [ABSTRACT FROM AUTHOR]

Conventional magneto-static finite element (FE) analysis of electrical machine design is time-consuming and computationally expensive. Since each machine topology has a distinct set of parameters, design optimization is commonly performed independently. This article presents a novel method for predicting key performance indicators (KPIs) of differently parameterized electrical machine topologies at the same time by mapping a high-dimensional integrated design parameters in a lower-dimensional latent space using a variational autoencoder (VAE). After training, via a latent space, the decoder and multi-layer neural network will function as meta-models for sampling new designs and predicting associated KPIs, respectively. This enables parameter-based concurrent multi-topology optimization. [ABSTRACT FROM AUTHOR]

This article presents a new type of surface-mounted three-phase permanent magnet synchronous motor with the same number of poles and slots which has obvious advantages in cogging torque. Since the same-pole and same-slot three-phase permanent magnet motor has three or more slot types and the slots are not evenly distributed on the circumference, this article adopts an accurate subdomain model that considers the position and slot width of each slot separately to perform an analytical calculation of the magnetic field. The motor is divided into three subdomains and modeled by Maxwell’s equations, and the magnetic scalar vector equation satisfied by each subdomain is solved by the method of separation of variables. A 24-pole 24-slot three-phase permanent magnet motor consisting of 13-pole 12-slot and 11-pole 12-slot is used to verify the correctness of the proposed analytical computational model. Compared with the finite element analysis, the proposed analytical model shows high accuracy in the calculations of the magnetic flux density of the three subdomains. [ABSTRACT FROM AUTHOR]

The peripheral magnetic field of the motor may cause magnetic field interference to the surrounding sensors, which would reduce the accuracy of sensors and affect the safety and concealment of vessel. This article explored the environmental magnetic field distribution law of a permanent magnet (PM) motor with two-pole parallel magnetization. A no-cogging magnetic field model was obtained by solving Maxwell equations, and the relationship between the air gap flux density and the environment flux density was built considering the motor cogging effect. In addition, a mathematical model of connections between the back electromotive force (EMF) and the environmental flux density was built, and the correctness of the model was verified by COMSOL. It is concluded that the circumferential and radial components of the environmental magnetic field are distributed sinusoidally, and the magnetic flux density modulus remains constant on the equidistant circumferential line, but attenuates squarely with the distance from the motor. It provides ideas for magnetic field analysis in the peripheral environment of other types of motors, sensors, and other anti-motor electromagnetic interference, magnetic field compensation for geomagnetic measurement, and motor fault diagnosis. [ABSTRACT FROM AUTHOR]

This article presents a new type of double stator swing rotating permanent magnet spherical motor (DSSRPMSM), which can realize swing, rotation, and helical motion and is used in industrial robots, gyroscopes, satellite communications, and other fields. The proposed spherical motor consists of two stators and a hollow rotor with permanent magnet (PM) poles on its inner and outer surfaces. Compared with most spherical motor with hollow coil and traditional PM synchronous motor, the structure of the motor is different and novel, and it is difficult to find a more perfect design theory and method. Thus, this article introduces the new idea of motor design in detail. First, the structure and working principle of the motor are introduced, and the original design of the motor is carried out. The 2-D rough estimation and 3-D FEM accurate simulation calculation are carried out, and the electromagnetic characteristics of the motor are obtained, including magnetic flux density distribution, torque, and loss. The simulation results meet the design specifications of the motor. A prototype was built and tested. The experimental results are in good agreement with the 3-D FEM analysis. The design method provides a theoretical basis for the design of this kind of spherical motor. The research results lay a foundation for the subsequent optimization of the motor. [ABSTRACT FROM AUTHOR]

A new partitioned stator field modulation machine (PSFMM) with H-shape permanent magnet (HPM) excitation (HPM-PSFMM) is proposed, which is evolved from the conventional flux-switching machine (FSM) and flux-reversal machine (FRM). The proposed HPM-PSFMM combines the merits of high reliability and good heat dissipation characteristic. In addition, it exhibits high torque production with low torque ripple. Based on the theory of electrical machine operation, the FSM and FRM can be transformed into PSFMM with interior permanent magnet (IPM) and surface-mounted PM (SPM) excitation by changing the position of PM excitation, respectively. It benefits to improve space utilization and increase slot area for a large number of armature windings. For reducing the flux leakage and enhancing the flux density in air gaps, the IPM and SPM excitation are combined into HPM excitation. The iron-pole rotor between the inner and outer stators acts the role of modulator to modulate the magnetic field excited by HPM excitation to couple with the armature reaction for converting electromechanical energy. The evolution process, operating principle, and key design parameters of the proposed HPM-PSFMM are presented. Finally, using the finite element analysis (FEA), it can be proven that the proposed HPM-PSFMM has the merits of high torque production, low flux leakage, low total harmonic distortion (THD), and low torque ripple when compared to other stator-PM machines, which is a desirable choice for high stability applications. [ABSTRACT FROM AUTHOR]

A new consequent-pole permanent magnet (CPM) machine with segmented structure/unequal teeth (CPM-SU machine) is proposed in this article. The segmented structure is adopted to decrease the torque ripple. To improve the torque density, the structure of unequal teeth is used in this proposed machine. The five-phase winding located in the stator is composed of three fractional-slot concentrated windings (FSCWs), which are helpful to improve the fault-tolerant capability. Permanent magnets (PMs) are placed in the rotor. To decrease the PM cost, V-type PMs and iron cores are arranged with the sequence of S-iron-S-N-iron-N. The magnetic field generated by PMs is investigated, which is helpful to demonstrate the working mechanism of this proposed CPM-SU machine. To verify the superiority of the proposed CPM-SU machine, a conventional CPM machine with unsegmented structure/equal teeth (CPM-UE machine) is proposed. The electromagnetic properties of these two machines, including the electromagnetic torque, the cogging torque, and the back electromotive force (back EMF), are analyzed by the finite element (FE) method. The simulating results show that the CPM-SU machine can exhibit excellent performances, such as low torque ripple and high torque density. [ABSTRACT FROM AUTHOR]

This article proposes the novel method of deriving torque and speed curve (TS curve) of the permanent magnet synchronous motor (PMSM) using the initial state finite element analysis (ISF) for the purpose of reducing the high calculation cost of the repetitive finite element analysis (FEA). The ISF is a method that conducts the FEA only for the initial rotor position. As the ISF neglects other periodic parts, the calculation time for analyzing the PMSMs can be drastically reduced. To verify the performance of the proposed method, the ISF and conventional method of full period FEA (FPF) with many steps were applied to three types of the PMSMs, interior PMSM (IPMSM), surface-mounted PMSM (SPMSM), and flux switching machine (FSM). The proposed method reduces the calculation time for deriving the TS curves of the SPMSM, IPMSM, and FSM as 86.35%, 89.39%, and 89.41%, respectively, compared with conventional methods of considering the periodic parts. The analysis accuracies at the operating points of each test models are 94.24%, 99.24%, and 99.86%, and the ISF ensures acceptable accuracy considering the reduced calculation time. Therefore, the ISF can be effectively used when deriving the TS curves of the PMSMs at the early design stage of the motors. [ABSTRACT FROM AUTHOR]

In this article, a dual-mechanical-port flux-switching permanent magnet (DMP-FSPM) motor is studied for achieving high-efficiency design and optimization. The key of this study is to propose an optimization design approach for broadening high-efficiency region, where the motor efficiency fitting curve and the speed–torque envelope curve are combined. First, the efficiency function is established according to the motor power and loss equation. Then, high-efficiency region boundary points are obtained by combination of the fitted efficiency curve and speed–torque envelope curve. Next, the efficiency of representative operating points is determined and optimized to realize the broadening of motor high-efficiency region. Finally, the effectiveness of the proposed method and the studied DMP-FSPM motor is verified by the study results and experiment test. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) machines have attracted much attention in the field of flywheel energy storage system (FESS) due to their merits of high power density and high efficiency. However, the flux generated by the PMs would cause large stator core loss during the idling state of FESS, which would reduce the energy conversion ratio and limit the application of FESS in long-term energy storage occasions. Addressing this issue, a novel dual-rotor single-stator coreless PM machine (DSSCPMM) with dual-flywheel is proposed in this article. The stator of the DSSCPMM is made of ceramic material, which can effectively eliminate the stator core loss. The rotor of the DSSCPMM contains inner and outer rotors, which are used as the flywheels and can be helpful to improve the energy storage density. First, the structure and operation principle of the proposed DSSCPMM are illustrated. Then, the influences of the key structure parameters and arrangement of PMs, winding configurations, and magnetization method on the electromagnetic performance of the proposed DSSCPMM are investigated. Finally, the optimized structure of the DSSCPMM is obtained and the efficiency is calculated. The result shows that the proposed DSSCPMM is a promising candidate for the application of FESS. [ABSTRACT FROM AUTHOR]

To realize brushless excitation for an electrical excitation synchronous generator (EESG), a brushless-induced double electrical excitation synchronous generator (IDEESG) with dc excitation is investigated in this study. The static magnetic field is established by injecting dc into the stator excitation windings that are added in the stator slots. Rotor windings are divided into two parts: induction coils and rotor excitation winding. The induction coils cut the static magnetic field and provide dc current for the rotor excitation winding after the rectification. The direction of the currents in the induction coils is constant because of the half-wave rectification. The magnetic flux generated by the currents in the induction coils and rotor excitation winding is added in the air gap to induce the armature coils in the stator. In this study, the structure and the operating principle are examined. The frozen permeability method is adopted to study the influence of the currents in the induction coils and the rotor excitation winding on the magnetic field distribution. The harmonic content of currents in the induction coils is analyzed using the Fourier series form and the effect of the harmonics on the output voltage is also studied. A 1.5 kVA prototype is fabricated to verify the correctness of theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]

This article proposes a novel axial field switched flux memory machine (AF-SFMM) which is analyzed by a combined analytical method. Compared with conventional axial field (AF) permanent magnet (PM) machines having magnets in the rotor side, the AF-SFMM benefits from good heat dissipation, high rotor robustness, and improved power density. Meanwhile, because of the utilization of low coercive force PM materials, the proposed machine can flexibly regulate air-gap flux. This analytical method is characterized by the combination of a quasi-3-D (quasi-3D) finite element method, a magnetomotive force–permeance-based method, and a virtual linear hysteresis model of low coercive force PM. In addition, compared with conventional time-consuming 3-D finite element analysis (FEA), the proposed method can improve the computational efficiency significantly with satisfactory accuracy. This makes the proposed combined analytical method suitable for preliminary sizing determination of AF-SFMM. Meanwhile, the effectiveness of the proposed analytical method is validated by FEA results. [ABSTRACT FROM AUTHOR]

A new type of hybrid magnet dual stator field modulation machine with different split ratios of stators (DSR-HMDSFMM) is proposed in this article, which has the merit of high torque density. The split teeth of stator sever as modulators to modulate air gap flux density based on the magnetic gearing effect for high torque production. The total split tooth number of inner stator is equal to that of outer stator because the pole pair numbers of armature reaction and permanent magnet (PM) excitation on rotor are equal. Furtherly, the inner and outer stators with different split ratios and same split tooth number are employed to increase torque production because armature windings with high winding factor and high turn number can be used. In addition, the employment of hybrid magnet excitation can increase space utilization and enhance the air gap flux density with low harmonic distortion. Therefore, the proposed DSR-HMDSFMM can achieve high torque production with the same volume and PM usage. In order to find the optimal split ratio match of stators, several DSR-HMDSFMMs with different combinations of split ratios are proposed and calculated. The configuration and operating principle are illustrated, together with electromagnetic performances of the proposed machines analyzed using finite element analysis (FEA). The FEA-predicted results show that the proposed HMDSFMM exhibits high air-gap flux density with low harmonic distortion and high torque density, which is promising for the direct-drive applications. [ABSTRACT FROM AUTHOR]

The flux density distribution in an induction machine (IM) can be obtained by a conventional winding function-based (CWFB) model for being incorporated in the machine’s core loss calculation using the Bertotti core loss function. However, in this CWFB analytical core loss prediction method, the slotting effects, magneto-motive-force (MMF) drops in the stator and rotor cores, and frequency-dependent $B$ – $H$ characteristics of the core are ignored for simplicity. In this article, an extended winding function-based (EWFB) model is proposed to overcome these shortcomings present in the existing analytical core loss prediction methods by sectioning the teeth, tooth tips, and yoke parts of the IM’s stator and rotor and accurately calculating the flux and core loss densities of each section taking into account the corresponding MMF drops and frequency-dependent $B$ – $H$ curve changes. The effectiveness of the proposed EWFB model over the CWFB model in predicting the total core loss of a laboratory 11 kW IM is validated via experiments at various operating points. [ABSTRACT FROM AUTHOR]

The conventional lap-winding high-speed permanent-magnet synchronous machine (HSPMSM) usually has a large interturn short-circuit (ITSC) current, seriously threatening the reliability. This article founds that the SC coil of the gramme-ring-winding HSPMSM is wound around the stator yoke, so the inductance of SC coil is considerable large and thus will cause a great reduction of ITSC current. The types of ITSC faults were first analyzed for a multistrand-gramme-ring-winding HSPMSM, and then, the ITSC characteristics and influencing factors were investigated based on finite-element (FE) method. The distribution of flux density is quite different from normal state, the SC current is far lower than that of the lap-winding HSPMSM, and the inductance of SC coil is fluctuant with rotation of rotor. By theoretical analysis of the inductance, the methods of increasing the height of stator yoke and using high-permeability CoFe alloy were proposed to further reduce the SC current. In addition, decreasing the strands number is beneficial to reduce the SC current density. [ABSTRACT FROM AUTHOR]

The circumferential and axial widths of permanent magnet (PM) pole and E-shape stator pole of linear rotary motor with interlaced PM poles are very influential to the back electromotive force (EMF) and the flux leakage analysis is complex, which causes difficulty in optimization of the motor structure. One of the key issues in optimization design is to calculate the flux leakage accurately. In this article, the main flux and side flux variation laws of stator pole are derived by analytical method. The flux leakage can be divided into the flux leakage between the PM and the mover, flux leakage on the stator tooth tip, and the flux leakage between the adjacent PM poles and stator pole. The 3-D flux leakage calculation model is built, which is suitable for the calculation of magnetic flux based on different motor operating principles. Then the rotational and rectilinear back EMFs are calculated by analytical method, which are consistent with the results analyzed by 3-D finite element method. [ABSTRACT FROM AUTHOR]

This article proposes a new hybrid-excited partitioned stator flux modulated machine with a dual-permanent magnet (HE-PSFMDPMM). The HE-PSFMDPMM employs consequent-pole (CP) permanent magnets (PMs) on the inner stator and Halbach array CP PMs on the rotor, which can yield abundant air-gap flux density working harmonics to increase the torque capability. Meanwhile, the field windings are housed in the inner stator to achieve flux weakening. The topology, working principle, and design optimization of HE-PSFMDPMM are investigated, respectively. The electromagnetic performances of HE-PSFMDPMM are analyzed and compared with that of a contrast model with conventional CP PMs on the rotor. The results indicate that by using dual-PM excitation, HE-PSFMDPMM can provide large flux linkage, high torque production with low torque ripple, and high efficiency. Meanwhile, a good flux weakening capability is obtained with the aid of direct current (dc) excitation. Moreover, compared with the contrast model, the proposed HE-PSFMDPMM with Halbach array CP PMs on the rotor can offer the merits of lower cogging torque and torque ripple, higher power factor, and better flux weakening capability. [ABSTRACT FROM AUTHOR]

A new partitioned stator hybrid excitation (HE) with an internal magnetic ring machine was proposed in this article. The key of the design is to adopt an inner magnetic ring to reduce the inside stator magnetic reluctance. As a result, the working magnetic field harmonics can be improved, which in turn improve the torque and flux regulation abilities. Besides, by following the design of partition stator, the space competition of permanent magnet, armature winding, and field winding can be effectively alleviated as compared with a single stator HE machine. The structure and operation principle of the conventional and proposed machines are described. Moreover, electromagnetic performances of both machines are compared by using finite element method. Theoretical and simulation analysis results show that the proposed machine can exhibit higher torque and enhanced flux regulation ability than the conventional one. [ABSTRACT FROM AUTHOR]

This article presents a novel slot permanent-magnet-assisted hybrid-magnet memory machine (SPMA-HMMM) with hybrid permanent magnets (PMs) in both stator yoke and slot opening. The key is each pair of yoke PMs is composed of one pole of high coercive force (HCF) PM and one pole of low coercive force (LCF) PM with flexible flux regulation. LCF PMs can be freely magnetized and demagnetized through dc current pulses, which are supplied by dc excitation coils wound on LCF PMs. This design leads to high efficiency of machine due to negligible field excitation loss. In this article, the machine configuration and operation principle are illustrated in detail. An equivalent magnetic circuit is modeled to unveil flux regulation and parallel excitation effect. Then, the electromagnetic performances of SPMA-HMMM under different magnetization states (MSs) are investigated, which verify flux regulation ability of the proposed machine with changeable MSs of LCF yoke PMs. [ABSTRACT FROM AUTHOR]

This article proposes an improved tubular single-phase permanent magnet linear oscillation actuator (SP-PMLOA) considering eliminating detent force for direct drive compressor applications. First, the flux tube method and Maxwell stress tensor are used to derive the end force and cogging force formulations based on the magnetic flux leakage of the magnet rings. Then, a novel model with minimum detent force is presented by finite element parametric sweeping. Finally, the electromagnetic performance of the three SP-PMLOAs is compared using 2-D finite element analysis (FEA), whose merits are evaluated, and the thermal distribution of the optimal PMLOA is analyzed using 3-D FEA. The predicted results show that the proposed structure not only can significantly reduce the detent force and the mover axial length but also can increase the thrust force-moving magnet mass ratio. [ABSTRACT FROM AUTHOR]

A typically new semi-analytical finite element approach has been used to calculate the force and moment of permanent magnet bearing (PMB) in this article. PMB stator and rotor consist of ring-type cylindrical magnets having an axial magnetization. This article focuses on the characterization of magnetic moment, stiffness matrix, model validation, and comparisons of the moment with other simulating software. This article also explains how angular stiffness or resisting magnetic moment of PMB improves with the change of rotor magnet length and positional shift of the rotor. [ABSTRACT FROM AUTHOR]

The space–time distribution characteristics of the air-gap magnetic field (AGMF) determine the electromagnetic performance of the motor. This article studies the influence of the inter-turn fault (ITF) on space and time harmonics of the AGMF, and the relevant fault characteristics are obtained through analysis and experiments. First, a theoretical analysis is deduced to compare the components of AGMF before and after the fault, and all space and time harmonics are obtained. Then, according to the parameters of the prototype, the distortion and components of space and time harmonics are analyzed. Also, the influence of rotor slot harmonics is considered to analyze the variations of time harmonics. Finally, a detection wire method that can directly measure the AGMF is proposed, and the spectrum results of the measured signals prove the correctness of the research in this article. A fault feature can be extracted based on the frequency band analysis, and it is not affected by load variations. The results obtained through analytical analysis, simulation, and experiment further improve the AGMF research of induction motors with ITF. [ABSTRACT FROM AUTHOR]

Surface mounted permanent magnet Vernier (SPM-V) machines, because of their high torque density and multi-pole structure, are promising candidates for low-speed direct-drive applications. To achieve high torque density, the SPM-V machines are generally designed with high gear ratios. Therefore, their operating frequencies can be much higher than those of the conventional SPM machines. This potentially increases the alternating current (AC) winding losses, especially those with form-wound coils proposed for high-power applications. This article investigates the AC losses (including skin effect, proximity effect, rotor PM induced, and circulating current losses) in form-wound stator coils of a 3 MW direct-drive SPM-V machine with different slot/pole number combinations. The study reveals that the SPM-V machines have significantly higher AC winding losses than their conventional SPM counterparts for similar operating conditions. To reduce the AC winding losses in SPM-V machines, a novel flux shunt concept is proposed along with other conventional techniques such as increasing the number of turns/coil (with terminal voltage being kept constant) and parallel strands/turn, providing extra clearance at slot opening. With the loss reduction techniques implemented, the SPM-V machines can achieve comparable efficiency but much higher torque density than their conventional counterparts. Moreover, the proposed flux shunt was also found to be very effective in reducing the potential risk of permanent magnet (PM) irreversible demagnetization, a key issue for SPM-V machines at high power ratings. [ABSTRACT FROM AUTHOR]

Stator and rotor cores of interior permanent magnet (IPM) motors are usually saturated, and the saturation distribution and saturation depth vary with the stator current. Also, their rotor structures are complex; hence, the saturation cannot be accurately reflected by a saturation factor. These considerations lead to the existing equivalent air-gap length models of induction motors and inset permanent magnet (PM) motors no longer suitable for IPM motors. Therefore, based on the consideration of stator and rotor saturation, this article proposes the equivalent air-gap length model of IPM motors expressed by magnetic potentials on the stator inner surface and the rotor outer surface. The proposed equivalent air-gap length model can accurately reflect the influences of complex structure and severe saturation of IPM motors. Compared with the existing models, the proposed one is no longer uniquely determined by motor structure parameters; it is also a function of stator current and rotor position. Furthermore, the obtained equivalent air-gap length model is combined with the winding function and the modified winding function to solve the inductances under different stator currents and different rotor eccentricity states. Finally, the proposed method is verified by both finite element analysis (FEA) and experiments. [ABSTRACT FROM AUTHOR]

In this article, two novel dual-stator machines with different biased permanent magnet (PM) configurations are developed and comparatively studied. For the proposed machines, the PMs are only located in the inner stator, but with different configurations, that is, surface-mounted PM (SPM) and interior PM (IPM), respectively. The machine topologies and operating principle are introduced first. Then, the electromagnetic characteristics, including open-circuit performance, torque characteristics, field-weakening capability, loss, and efficiency, are comprehensively analyzed and compared by finite-element method (FEM). The experimental validation is conducted to verify the FEM analyses. [ABSTRACT FROM AUTHOR]

This article presents a method to reduce cogging torque in permanent magnet (PM) machines from dynamic control based on harmonic torque counteract (HTC). We find the possibility of dynamic cancellation of cogging torque and harmonic torque by studying their generation mechanism and period characteristics, and further study the current harmonic injection scheme for cogging torque reduction. Further, two case studies of an integer slot PM machine and a fractional slot PM machine based on finite element analysis well validate the proposed method. Among them, the cogging torque of a 6-slot/2-pole PM synchronous machine is weakened from 932.0 to 56.2 mN.m, with a weakening ratio of 94.0%, and the cogging torque of the other with 6-slot/4-pole is weakened from 1.23 N.m to 44.21 mN.m, with a weakening ratio of 96.4%. The theory of this article can be extended to PM machines with other different pole/slot combinations and topologies. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) motors have become great alternatives to traditional induction motors. Overhang, on either the rotor or the stator, is commonly used in PM motors. In this study, various alternatives of stator or rotor overhang in PM synchronous motors are investigated in detail. Both asymmetric and symmetric overhang cases are considered in the article. The impact of overhang on the torque quality and torque densities is investigated using 3-D finite element analysis (3D-FEA). Axial magnetic forces during assembly with and without overhang are also simulated and variation of axial force for different cases of overhangs is explored. A prototype PM motor with rotor overhang is used to validate the analyses experimentally. [ABSTRACT FROM AUTHOR]

In this article, a new consequent-pole segmented dual-stator permanent magnet (CPSDSPM) machine, which is used for some high-torque and low-speed applications, is proposed. This proposed machine adopts two stators, in which the external stator is segmented into three parts. The intermediate rotor is sandwiched between the internal stator and the external stator. Due to a particular coupling effect between the internal stator and the external stator, the CPSDSPM machine can inherently exhibit excellent flux-enhancing ability and output capability. The configuration of this proposed machine is introduced. The working mechanism especially the coupling effect is discussed by analytical models. The electromagnetic properties, such as the no-load back electromotive force (back EMF), the cogging torque, the output capability, and the torque ripple, are all calculated and analyzed by the finite element (FE) method. It can be seen that the simulating results can verify the correctness of the theoretical analysis and the superiority of the proposed CPSDSPM machine. A prototype machine is fabricated and tested to validate the results of the FE analysis. [ABSTRACT FROM AUTHOR]

In this article, the split-tooth stator-slot permanent-magnet (ST-SSPM) machines with different permanent magnet (PM) arrangements are comprehensively analyzed. Four types of ST-SSPM machines are first introduced and classified by the positions and polarities of PMs. Then, the operation principles are elaborated and the slot–pole combinations are derived from the view of the field modulation theory. Besides, four types of ST-SSPM machines with different slots and rotor poles are globally optimized to achieve maximum torque and minimum torque ripple. Furthermore, the electromagnetic performances of the optimal designs are thoroughly analyzed by using the finite-element analysis (FEA), including the cogging torque, back electromotive force (EMF), steady torque, PM utilization ratio, loss, efficiency, and PM demagnetization. Finally, some conclusions are drawn based on the optimal designs and analyzed results. [ABSTRACT FROM AUTHOR]

This article proposes a new axial dual-stator flux-switching permanent magnet (FSPM) machine for high-speed applications. The machine adopts a fractional slot distributed winding, which has a higher winding factor, efficiency, and torque density. First, the high-speed FSPM machine topology and operating principle are introduced. By employing the winding complementarity principle, the unfavorable even harmonics of a single stator in the FSPM machine can be counteracted, resulting in an essentially sinusoidal permanent magnet (PM) flux-linkage as well as effectively reduced cogging torque and torque ripple. Second, based on the 3-D finite element method (FEM), both the no-load and on-load electromagnetic performances are obtained. Compared with the other three FSPM machines, the advantages of the proposed machine are highlighted. Finally, a high-speed FSPM prototype is manufactured and a test platform is built to measure the no-load and on-load performances, which verifies the theoretical analysis and simulated results. [ABSTRACT FROM AUTHOR]

This article employs grain-oriented (GO) silicon steel in an axial-flux permanent magnet (AFPM) machine to improve its torque and efficiency. Rolling direction of the GO material have been studied to ensure the machine’s main magnetic flux passes through the easy magnetization direction. Based on the study of the electromagnetic characteristics of AFPM machine, GO silicon steel is laminated to form a stator according to a certain lamination direction. The torque and efficiency of the proposed machine with GO material shows an increase in comparison with that of the conventional non-oriented (NO) silicon steel machine under identical conditions. In addition, an equivalent magnetic circuit model is established to illustrate little difference of electromagnetic property under no-load condition for the yokeless stator AFPM using two kinds of silicon steel sheet. Furthermore, a AFPM machine with stator yoke is also established to highlight the superiority of GO in the application of the AFPM machine with yokeless stator. [ABSTRACT FROM AUTHOR]

Flux switching motors (FSMs) with conventional stator slots have a relatively low copper slot filling factor. In this article, a new octane modular stator with pentagon-shaped slot electrically excited FSM (EEFSM) that has a comparatively higher copper slot filling factor is analyzed analytically to reduce computational complexity, high computational time, and high drive storage. The analytical results of the proposed EEFSM are validated via the finite element method. Furthermore, the initial design is optimized to improve the electromagnetic performance, and finally the prototype is fabricated and tested experimentally. There is good agreement among the analytical, finite element analysis (FEA), and experimental results with variations of 3%–5%. The average torque of the optimized design has improved by 30%, cogging torque is suppressed by 36%, and torque ripples have reduced by 38%, which have improved the performance of EEFSM in terms of low acoustic noise, low vibration, and longer motor lifetime. The proposed octane modular stator can be easily unfolded for windings maintenance, coils placement, and motor transportation in case of large-size applications. [ABSTRACT FROM AUTHOR]

Ultra-high-speed (UHS) surface-mounted permanent-magnet synchronous motors (SPMSMs) are widely used for driving air compressors. UHS SPMSMs can suffer from high stator iron loss and rotor eddy current loss due to their high rotational speed and changes in the magnetic flux density when loading. Since these losses do not have a linear trend but change according to the motor design parameters, mathematical models cannot always predict them. This study aims to design UHS SPMSMs based on a kriging surrogate model that takes into account the stator iron loss and rotor eddy current loss. Since the kriging surrogate model is highly predictive for nonlinear inputs, it is the perfect candidate to take into account the stator iron loss and rotor eddy current loss. The design proposed in this study allowed to minimize the size and losses of a motor that satisfied the power specification. [ABSTRACT FROM AUTHOR]

Axial-flux magnetic-geared double-rotor machines (AMGDRMs) are characterized as a potential key component of the power-splitting system in hybrid electric vehicles (HEVs), but its conventional configuration suffers from the high axial magnetic force. In this article, an interior-modulating-rotor AMGDRM (IMR-AMGDRM) is proposed to solve this problem. To reduce computation burden, an analytical model of the IMR-AMGDRM is proposed based on the subdomain method. The analytical expressions of the magnetic field distribution and electromagnetic performances, such as torque and axial force, are developed. Finally, the results of the proposed analytical model are compared with those of the 3-D finite element analysis (FEA). The influences of the geometrical parameters of the ferromagnetic pole pieces and permanent magnets (PMs) are also investigated by the analytical model and 3-D FEA. The accuracy and the cause of the calculation error of the analytical model are studied. [ABSTRACT FROM AUTHOR]

Permanent magnet (PM) synchronous motors have become excellent alternatives for traditional induction and dc motors in numerous applications in recent years. Therefore, torque density and efficiency improvements in the development of PM synchronous motors have become a significant issue. In this study, various PM synchronous motor alternatives are proposed with both non-oriented (NO) and grain-oriented (GO) silicon steel material in the same stator in order to increase the power density and efficiency. A detailed performance comparison using 2-D/3-D finite element analysis (FEA) is completed and a feasible stator design is manufactured. The proposed design with GO material is also compared with a conventional PM motor with NO stator steel. As a result of the investigations, it is observed that the proposed motor with GO material in the stator has higher torque density and efficiency as opposed to the conventional PM motor. [ABSTRACT FROM AUTHOR]

This article proposes a new partitioned stator hybrid-excited flux reversal machine with dual-PM (PS-HEFRDPMM), in which field windings are placed in the inner stator and permanent magnets (PMs) are employed on both the rotor and outer stator. By utilizing dual-PM excitation, the proposed PS-HEFRDPMM is able to introduce the bidirectional flux modulation effect to transmit high torque production. In addition, a good flux weakening capability can be obtained by using dc current to regulate air-gap magnetic field, which is beneficial to expand the speed range of machine. The machine topology, operating principle, and design considerations of PS-HEFRDPMM are described, respectively. The electromagnetic characteristics of PS-HEFRDPMM under different excitation states are comprehensively analyzed using finite element method. The results show that the proposed PS-HEFRDPMM can provide the merits of high toque capability with low torque ripple, good over-load torque capability, high power factor and efficiency, as well as good flux weakening capability. [ABSTRACT FROM AUTHOR]

Due to the bidirectional field modulated effect, the dual-permanent-magnet-excited (DPME) machine relies on the countless airgap flux density harmonics with specific pole-pair numbers (PPNs) to produce stable torque or effective back electromotive force (EMF). Regarding the generation of back EMF, there is no doubt that the flux density harmonics which make a negative contribution will reduce the performance of DPME machine. However, to the best of our knowledge, there is very little research on the identification of field harmonics which play a negative role in the generation of back EMF. In this article, the partial-analytical-method (PAM) is proposed to quantitatively identify the field harmonics. First, the PAM is described in detail, and the ratio of contribution (RoC) is defined to assess the contribution of field harmonics to back EMF. Then, the PAM is applied to a 12/10 DPME machine. The identification results show that two of the five types of field harmonics, i.e., Type-II and Type-V, make a negative contribution to back EMF; the RoCs of which are −2.94% and −4.32%, respectively. In these two types of harmonics, the ones with PPN = 22 are mainly responsible for the negative contribution to back EMF, which needs attention at the outset of the design. [ABSTRACT FROM AUTHOR]

This article presents an investigation into the application of a magnetically geared pseudo-direct-drive (PDD) electrical machine in a floating tethered 6 kW, 100 r/min marine current turbine. The turbine is designed to harness the energy from ocean currents, in regions with relatively high-speed water flows at depths that are a long distance from the seabed and cannot be economically exploited by conventional fixed turbines. The marine current turbine is a robust, easy to service, and cost-effective solution for regions with variable or fixed sea depth of more than 60 m. This article presents the electromagnetic design and analysis of the PDD generator, and predicted performance such as efficiency, which is compared with dynamometer measurements on a prototype PDD generator. Furthermore, test results on a demonstrator marine turbine in a towing tank are also presented. [ABSTRACT FROM AUTHOR]

The need for combining two mechanical powers with electrical power is a vital part of many applications, such as hybrid electric vehicles. The magnetic geared surface permanent magnet (MGSPM) motor is a compact and efficient way of achieving this goal. However, their complex structure demands time-consuming optimizations, which requires a large number of simulations. In this context, a fast and accurate simulation method is required to reduce the design and optimization time. In addition to speed and accuracy in considering the complex structures of the machine, as the saturation effect has a major impact on the accuracy of the simulations in these machines, it must be included in the method. To tackle this problem, in this article, a hybrid subdomain (SD) and magnetic equivalent circuit (MEC) model is proposed, considering the saturation effect of the iron parts using current distributions in the SD model on the surfaces of modulators and rotor core, as well as in the stator slots. These currents are calculated using the MEC model of the respective parts and Ampere’s law. Furthermore, an example motor is simulated both using the proposed method and the FE method, and the accuracy of the method both for prediction of magnetic flux density inside iron parts and prediction of flux linkages of the machine for a variety of designs and excitations is verified. [ABSTRACT FROM AUTHOR]

There are many space harmonics in the stator magnetomotive force (MMF) of fractional-slot concentrated winding (FSCW). These harmonics will produce high eddy current losses in the permanent magnet (PM), which will reduce motor efficiency and affect motor performance. Aiming at the above problems, the harmonic components of traditional stator MMF are first analyzed in this article, and then, a novel space-shifted unequal-turn winding structure is proposed for dual three-phase fractional-slot permanent magnet synchronous motors (PMSMs). Meanwhile, the sub- and super-harmonics in the stator MMF can be simultaneously eliminated using the proposed winding structure. To verify the effectiveness of the proposed structure, an 18-slot/8-pole motor and a 30-slot/14-pole dual three-phase fractional-slot PMSM with low space harmonic are designed by using the proposed space-shifted unequal-turn winding structure based on the analysis of nine-slot/eight-pole and 15-slot/14-pole motors. Finally, by comparing the finite element analysis (FEA) results, it is verified that the dual three-phase PMSM motor with the proposed structure has smaller eddy current losses in PM and better motor performance. [ABSTRACT FROM AUTHOR]

A reaction sphere (RS) is a novel and promising actuator for microspacecraft attitude control systems (ACSs). However, the detection of the motor status, such as the rotating speed of the spherical rotor, is a difficult task. The equivalent circuit can be used to predict the motor status. This article presents an improved multi-layer transfer-matrix method for the equivalent circuit parameters’ calculation. Results compared with a finite element analysis (FEA) show that the proposed analytical model achieves an acceptable accuracy within the operating speed range. Meanwhile, its computation time is 0.072 s, on average, which is only 0.0003% of the FEA. [ABSTRACT FROM AUTHOR]

In this article, a 2-D analytical model is presented for brushless double mechanical port flux-switching permanent magnet machines (BDMPFSPMMs). The BDMPFSPMM is an appropriate candidate to be employed as the electric motor in hybrid electric vehicles (HEVs) due to integrating two rotors and two stators into a compact structure. The radial and tangential components of the magnetic flux density are calculated due to permanent magnets and armature currents in each active region of the machine based on the subdomain method. The effects of the saliency on both the rotor and stator structures as well as their interactions are considered. The approach can be used for the magnetic field calculation in BDMPFSPMMs with any combination of rotor- and stator-pole numbers. Based on the computed magnetic flux density, electromagnetic torque, self and mutual inductances, flux linkage, induced voltage, local traction, and unbalanced magnetic force (UMF) are obtained. To validate the proposed model, the analytical results are compared with those obtained from the finite element method (FEM). [ABSTRACT FROM AUTHOR]