Search

This paper proposes a novel consequent‐pole dual‐stator linear permanent magnet vernier machine (DS‐LPMVM) with PM in the mover slot opening, which has a bi‐directional flux modulation effect. The novelty of the proposed machine consists of consequent‐pole double‐sided topology with toroidal windings placed in the mover slot, as well as PMs both on the stator and mover slot to improve the air gap magnetic field. The dual‐stator adopts misalignment structure to suppress detent force and produce steady thrust. The electromagnetic parameters of the proposed DS‐LPMVM are evaluated and quantitatively compared with the conventional linear permanent magnet vernier machine (C‐LPMVM) in terms of air‐gap flux density, no‐load back EMF, inductance, and thrust. The geometrical parameters are designed to reduce the detent force. By analyzing the optimized structure parameters of the two machines, the good electromagnetic performances of the proposed machine are verified by the finite element method (FEM) and semi‐analytical method, and both results of the two methods are basically the same. It is found that the amount of PMs for the proposed machine is reduced by 20% compared to the C‐LPMVM, but the average thrust is increased by 20.7% and the thrust ripple is reduced to 4.04%. The results show that the proposed DS‐LPMVM has better flux modulation effect and thrust characteristics than C‐LPMCM. Finally, a 12‐slot, 10‐pole pairs prototype was manufactured and tested. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Permanent magnet assisted synchronous reluctance motor (PMaSynRM) has been widely concerned, but the research on the vibration and noise of this kind of motor is relatively limited. In addressing the problem of significant vibration noise caused by radial electromagnetic force waves in PMaSynRM, the research explored a motor vibration and noise suppression solution involving stator slotting and rotor magnetic isolation hole opening. The study analyzed the impact of different slotting parameters on the radial electromagnetic force and air gap magnetic flux density of the motor and compared it with the solution involving slotting of the stator teeth only and magnetic isolation hole opening of the rotor only. Finally, the modal, vibration response, and noise response of the motor after slotting are analyzed and verified. The results show that the amplitude of radial electromagnetic force and the total harmonic distortion rate of the air gap magnetic flux density of the motor are significantly reduced by opening the stator auxiliary slot and rotor magnetic isolation hole. The maximum vibration acceleration of the motor is reduced by 33.44 mm/s2, and the peak A-weighted sound pressure level of the motor decreases by 5.68 dBA. [ABSTRACT FROM AUTHOR]

Cascading rotor and stator in axial flux permanent magnet (AFPM) machine is a beneficial concept to increase the power density without increasing the diameter of the machine. Multi-stage AFPM can provide higher torque capability in applications requiring high power density. In this regard single-stator double- rotor (SSDR) and double-stator single-rotor (DSSR) are efficient machines compared to single -stage AFPM. Since SSDR and DSSR are also considered modular units to make multi-stage AFPM, like single-stage AFPM, this paper makes a comparison with analysis between SSDR and DSSR AFPM machines. Based on 3-D finite element analysis (FEA), the air-gap magnetic flux, voltage, current, torque, torque ripple, power and power density, efficiency are comparatively investigated to evaluate their performance. Results show that fully coreless topology only be achieved in SSDR AFPM machine with a higher power density. Finally, a prototype multi-stage coreless generator has been developed using a single stator double rotor (SSDR) configuration to justify the fully coreless concept. This prototype coreless generator eliminates eddy current losses and reduces weight, making it a suitable option for certain portable applications. [ABSTRACT FROM AUTHOR]

The effect of winding chording on five-phase synchronous reluctance motor (SRM) modelled in phase variables is presented. The stator winding configuration is shifted a pole pitch from a fullpitch configuration to a 54 degrees over-full-pitched configuration incorporating the effect of 3rd harmonic of the air-gap magneto-motive force in the inductance equations. The models are monitored on starting, synchronism, loading, faults and loss of synchronism. These are considered simultaneously with vector potential, rotor speed, air-gap flux linkage and winding current. The phase variable (analytical) models have been simulated by using MATLAB/Simulink software while ANSYS Maxwell software has been used to simulate the finite element model (FEM) of the motor for corresponding chording ranges for comparison on direct online starting (DOL). Under all conditions considered in the work, the detailed results are presented and very close similarity is observed between the analytical and the nearly ideal FEM model for all chording ranges and the similarity is enhanced with increase in chording angle. [ABSTRACT FROM AUTHOR]

Introduction. The drive electric motor is one of the key components in the traction chain of an electric vehicle. Traditional radial flux motors used in electric vehicles, which use permanent magnets or induction motors in an electric field, are experiencing significant development aimed at optimizing their weight and cost. However, it can only go so far, so switching to a completely different type of machine, such as an axial flow, might be a good alternative. The novelty to this item is an axial flux permanent magnet motorization with non-slotted TORUS-NS rotor (single interior stator with two external rotors North-South) type housed in the wheel of the vehicle; this allows power to pass directly from the motor to the wheel, increasing the efficiency of the motor. System complexity is also less, as the transmission, differentials and driveshaft are eliminated. Purpose is to equip the electric car and choose the motor adapted to the application and the available space. The smaller size and weight allows for a lighter vehicle and more batteries, thus increasing range. The focus on customization is because vehicle performance is so dependent on the quality of the vehicle architecture, battery pack and axial flux motor design. The results obtained are in good agreement of accuracy, in particular the flux density at the air gap. The investigation is carried out by the finite element method. Machine model was run on Maxwell 16.0 business code. [ABSTRACT FROM AUTHOR]

The effect of unbalanced magnetic force and torque ripple of on the output performance of a double stator switched-flux permanent magnet machine would be investigated and compared, with particular reference to the machine's varying rotor pole number. The finite element analysis (FEA) predicted machine parameters are: unbalanced magnetic force (UMF), total harmonic distortion (THD), torque ripple (Tr), cogging torque and static torque. The considered machine types having 10-, 11-, 13- and 14-rotor pole numbers are designated as: 6S/10P, 6S/11P, 6S/13P and 6S/14P, respectively; 6S represents six (6) stator slot or teeth number. It is revealed that the machine types that have odd number of rotor poles would have lower machine output characteristics such as: low cogging torque, low torque ripple and low total harmonic distortion of the voltage, compared to the ones that have even number of rotor poles; though, with higher amount of unbalanced magnetic force on the rotor. Further, the sensitivity of the machine's output performances due to electric loadings is higher than its corresponding response as a result of machine's varying rotational speed. More so, the machine types having odd number of rotor poles would have higher air gap flux density magnitudes; and would also exhibit better average torque per magnet usage, which is desirable for reduced cost implications. [ABSTRACT FROM AUTHOR]

Inter-turn short circuit in the excitation windings of synchronous condensers is a common fault that directly impacts their normal operation. However, current fault analysis and diagnosis of synchronous condensers primarily rely on voltage-balanced conditions, while research on short-circuit faults under unbalanced voltage conditions is limited. Therefore, this paper aims to analyze the fault characteristics of inter-turn short circuits in the excitation windings of synchronous condensers under unbalanced grid voltage. Mathematical models were developed to represent the air gap flux density and stator parallel currents for four operating conditions: normal operation and inter-turn short circuit fault under balanced voltage, as well as a process without fault and with inter-turn short circuit fault under unbalanced voltage. By comparing the harmonic content and amplitudes, various aspects of the fault mechanism of synchronous condensers were revealed, and the operating characteristics under different conditions were analyzed. Considering the four aforementioned operating conditions, finite element simulation models were created for the TTS-300-2 synchronous condenser in a specific substation as a case study. The results demonstrate that the inter-turn short circuit fault in the excitation windings under unbalanced voltage leads to an increase in even harmonic currents in the stator parallel currents, particularly the second and fourth harmonics. This validates the accuracy of the theoretical analysis findings. [ABSTRACT FROM AUTHOR]

Multiple factors and consequences may lead to a stator winding fault in an external rotor permanent magnet synchronous motor that can unleash a complete system shutdown and impair performance and motor reliability. This type of fault causes disturbances in operation if it is not recognized and detected in time, since it might lead to catastrophic consequences. In particular, an external rotor permanent magnet synchronous motor has disadvantages in terms of fault tolerance. Consequently, the distribution of the air-gap flux density will no longer be uniform, producing fault harmonics. However, a crucial step of diagnosis and controlling the system condition is to develop an accurate model of the machine with a lack of turns in the stator winding. This paper presents an analytical model of the stator winding unbalance fault represented by lack of turns. Here, mathematical approaches are used by introducing a stator winding parameter for the analytical modeling of the faulty machine. This model can be employed to determine the various quantities of the machine under different fault levels, including the magnetomotive force, the flux density in the air-gap, the flux generated by the stator winding, the stator inductances, and the electromagnetic torque. On this basis, a corresponding link between the fault level and its signature is established. The feasibility and efficiency of the analytical approach are validated by finite element analysis and experimental implementation. [ABSTRACT FROM AUTHOR]

The objective of this article isto developa comprehensive mathematical model of a three-phase induction motor to facilitate stator interturn (SIT) fault related study. A detailed analytical model that includes accurate inductance modeling considering rotor slot harmonics (RSH) under healthy as well as SIT faults is described. The proposed model is developed analytically in a step-by-step manner incorporating the features of RSH. A detailed but simplified analysis considering both magnetomotive force harmonics and air-gap flux harmonics has been presented. An asymmetric model is proposed, including SIT faults, in a single phase of the induction motor in the next stage of the modeling. The effect of saturation has also been considered in the model. The proposed model is validated by comparing the simulation results in transient, steady state, and frequency domain with the experimental results. Comparison shows a high degree of correlation with the results of the actual motor. The contributions of this work are justified by comparing the proposed model with the existing models. This article also shows that a frequency signature related to RSH present in the line current is capable of characterizing the SIT faults. [ABSTRACT FROM AUTHOR]

Shaded pole induction motors’ theoretical analysis is quite difficult because of the presence of strong harmonic components and the elliptical rotating field. The change of air gap reluctance is affecting the air gap flux distribution and thus the performance of the motor. In the study, the effect of the change in the SPIM’s stator, rotor and squirrel cage on the performance of the motor is analysed by the Finite Element Method. The flux distributions and torque values of the closed-interpoles type and the stator with different interpoles clearances are obtained. The effects of single and double cage structures in the rotor part and the effects of copper and aluminium cage materials in the squirrel cage were analysed. According to the analyses, it was determined that the single cage motor with aluminium cage material exhibited the best torque performance with a torque value of 132.78 mNm. [ABSTRACT FROM AUTHOR]

This article proposes a hybrid evaluation method of electromagnetic force and vibration for electrical machines considering high-frequency current harmonics caused by the inverter. First, the permeance and armature magnetomotive force (MMF) is calculated based on the virtual MMF and the slot matrix. Then, the air-gap flux density and electromagnetic force construction process under arbitrary current is thoroughly studied. The vibration transfer function is obtained by utilizing the modal analysis and the modal test. Finally, the vibration can be calculated according to the modal superposition method. By applying this method to an interior permanent magnet machine, it can significantly reduce the computation efforts compared with the multiphysics procedure due to the extensive use of the finite-element method. In addition, the accuracy of this method is validated by conducting an experimental study. [ABSTRACT FROM AUTHOR]

In this paper, the boundary discretization method is used to improve the traditional subdomain model. The improved model can be used to calculate the magnetic field distribution in the region containing non-orthogonal boundary, avoiding the influence of the simplified stator slot or permanent magnet shape on the results in calculating the motor magnetic field using the traditional subdomain model. In addition, the improved subdomain model can also be used to calculate the air-gap flux density when the rotor is eccentric, instead of segmenting the air-gap to an equivalent state without eccentricity. The calculation object of this paper is a surface-mount permanent magnet motor with a rectangular stator slot. The air-gap flux density under no-load and load conditions is calculated, respectively. Since the improved subdomain model does not need to simplify the stator slot shape, the magnetic potential in the stator slot is also calculated. Finally, the air-gap flux density under rotor eccentricity is calculated, and the influence of the calculating parameters on the results of the improved subdomain model is discussed. All the calculated results are compared with those obtained by the finite element method, which verifies the accuracy of the improved calculation model. [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]

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]

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]

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]

This paper proposes an artificial neural network for monitoring and detecting the eccentric error of synchronous reluctance motors. Firstly, a 15 kW synchronous reluctance motor is introduced and took as a case study to investigate the effects of eccentric rotor. Then, the equivalent magnetic circuits of the studied motor are analyzed and developed, in cases of dynamic eccentric rotor and static eccentric rotor condition, respectively. After that, the analytical equations of the studied motor are derived, in terms of its air-gap flux density, electromagnetic torque, and electromagnetic force, followed by the electromagnetic finite element analyses. Then, the modal analyses of the stator and the whole motor are performed, respectively, to explore the natural frequency and the modal shape of the motor, by which the further vibrational analysis is possible to be conducted. The vibration level of the housing is furtherly studied to investigate its relationship with the rotor eccentricity, which is validated by the prototype test. Furthermore, an artificial neural network, which has 3 layers, is proposed. By taking the air-gap flux density, the electromagnetic force, and the vibrational level as inputs, and taking the eccentric distance as output, the proposed neural network is trained till the error smaller than 5%. Therefore, this neural network is obtaining the input parameters of the tested motor, based on which it is automatically monitoring and reporting the eccentric error to the upper-level control center. [ABSTRACT FROM AUTHOR]

Compared with the single‐stator permanent magnet synchronous motor(SS‐PMSM), the double‐stator permanent magnet synchronous motor(DS‐PMSM) can make full use of the space in the motor cavity to make it have higher torque density, so it is more suitable for direct‐drive occasions with low‐speed and high‐torque. This paper aims to design and compare the parameters and performances of DS‐PMSMs with four different rotor structures: 1)Series magnetic circuit of radial magnetised single‐layer permanent magnet(type Ⅰ), 2)Series magnetic circuit of radial magnetised double‐layer permanent magnet(type Ⅱ), 3)Parallel magnetic circuit of radial magnetised double‐layer permanent magnet(type Ⅲ), 4)Parallel magnetic circuit of tangential magnetised permanent magnet(type Ⅳ). Firstly, the equivalent magnetic circuit method is used to analyse the magnetic circuits of the four DS‐PMSMs. Next, the finite element analysis tool is used to compare the performances of the four DS‐PMSMs with the same volume. Their air‐gap flux density, no‐load back‐EMF, cogging torque, torque characteristics, moment of inertia, rotor loss and efficiency are quantitatively analysed and compared. Finally, this paper provides guidance and suggestions for the selection of the rotor structure of DS‐PMSM. [ABSTRACT FROM AUTHOR]

A comparative study of new partitioned stator hybrid excitation axial flux switching permanent magnet (HEAFSPM) motors with different partitioned excitation stator topologies for in-wheel traction applications is presented in this paper. The realization approaches of the partitioned stator HEAFSPM motor are discussed, and the motor topology with windings and permanent magnets (PMs) separately setting on different stators is selected in view of the advantageous structure for thermal management. On this basis, two partitioned excitation stator topologies including C-type tooth core and T-type tooth core stator configuration are proposed, and the air-gap flux modulation and flux regulation principle of the motors are analyzed. In addition, the design method of the partitioned stator HEAFSPM motor considering the effect of hybrid excitation sources is provided, and the two motors with different tooth cores are designed respectively. Meanwhile, for a fair comparison, the multiple objectives optimization method coupled with the sensitivity analysis is employed to optimize the two motors. The electromagnetic performances, anti-demagnetization capability, and flux regulation performance of the two motors are all investigated in detail. Finally, two prototype motors are fabricated and tested. Both the theoretical analysis and experimental results verify the effectiveness and reasonability of the motor. [ABSTRACT FROM AUTHOR]

Variable speed, permanent magnet synchronous machines with hybrid excitation have attracted much attention due to their flux-control potential. In this paper, a design of permanent magnet axial flux machines with iron poles in the rotor and an additional electrically controlled source of excitation fixed on the stator is presented. This paper shows results pertaining to air-gap flux control, electromagnetic losses, electromagnetic torque, back emf and efficiency maps obtained through field-strengthening and weakening operations and investigated by 3D finite element analysis. Moreover, the temperature distribution of the machine was analyzed according to the fluid–thermal coupling method. The presented machine was prototyped and experimentally tested to validate the effectiveness of numerical models and achieved results. [ABSTRACT FROM AUTHOR]

This article proposes a swirling actuator that uses the electromagnetic radial force and mechanical gears to generate rotational torque. The proposed actuator generates a rotating radial force between an inner stator and a swirler. The gears on the swirler and outer rotor convert the circular motion of the swirler to low-speed rotor rotation. Thus, the proposed actuator is aimed at low-speed high-torque applications. In this study, the air-gap radial flux density and electromagnetic radial force are investigated analytically and verified through finite-element analysis. The static radial force and output torque are measured in a prototype of the actuator. The system efficiency and the gear efficiency are evaluated. A peak torque density of 27 Nm/L with a small volume of 0.16 L is realized in the prototype. [ABSTRACT FROM AUTHOR]

This paper gives a comprehensive comparison among two fault-tolerant axial field modular flux-switching (AFFSPM) machines with different stator modular segments (U- and E-core) and stator-slots/pole-pairs combinations. The topologies of two AFFSPM machines are introduced, each with two feasible stator slots and rotor pole-pairs combinations with high winding factors based on the slot-conductor back-EMF star vectors theory. Then, the static performance including the air-gap flux density, flux linkage, back-electromagnetic force (back-EMF), and electromagnetic torque are analyzed and compared. Moreover, the fault-tolerant capability is then investigated by the torque performance under one- and two-phase open-circuit conditions in which the corresponding fault-tolerant control strategies are applied. The predicted results confirm that the 6-stator slot/11-rotor-pole-pair E-core AFFSPM machine exhibits the best performance of the four candidates. [ABSTRACT FROM AUTHOR]

This article proposes a new maximum torque per ampere (MTPA) control strategy for an induction motor (IM) controlled by the scalar (v/f) method. In scalar control, constant air-gap flux control is generally adopted for IM drives to provide the same torque capability in all operating ranges. However, this control method results in poor motor efficiency due to excessive stator current at light loads. This work proposes a new MTPA control method to minimize the stator current amplitude based on reactive power without measuring the rotor mechanical speed, resulting in improved system efficiency at light loads. In addition, this method proposes an online machine parameter compensation method. Thus, this proposed method is robust to parameter variations. Simulation and experimental results are provided to verify the performance of this MTPA control strategy. [ABSTRACT FROM AUTHOR]

In this paper, superposition methods including the superposition of a single stator tooth and the superposition of a single rotor tooth, are proposed to predict the open-circuit performances of flux-reversal permanent magnet (FRPM) machines. By the proposed superposition methods, the electromagnetic performances, such as air-gap flux density, electromotive force, cogging torque, and unbalanced magnetic pull (UMP) are investigated and verified by 2D finite element analysis (FEA). Further, according to the superposition methods, cogging torque reduction techniques can be acquired from both stator side and rotor side. In addition, the influence of stator-slot/rotor-pole-pairs (slot/pole) combination on UMP is also studied, and consequently, a reasonable slot/pole combination rule is suggested to avoid UMP. Then, an improved configuration for UMP reduction is also investigated and verified by FEA. Finally, the prototype machines are manufactured and tested to further verify the theoretical analysis and FEA predictions. [ABSTRACT FROM AUTHOR]

For a marine electrical machine, its high power density and large electromagnetic (EM) load tend to bring high saturation to the magnetic circuit. When the non-linearity of ferromagnetic material is not taken into consideration, large errors will appear in the calculation of air-gap flux density and EM force wave. Considering the radial and tangential EM force waves that cause the stator core to vibrate and deform are the primary sources of EM vibration of a non-salient pole synchronous generator (NSPSG), this paper introduces a semi-analytical method of calculating the radial and tangential EM force waves, with the non-linearity of ferromagnetic material taken into account. The method includes the distributed magnetic circuit method (DMCM), the separation variable method (SVM) and the complex variable conformal transformation method (CVCTM). First of all, the radial air-gap flux density is obtained by using the DMCM to calculate the no-load magnetic circuit of the NSPSG and dealing with the non-linearity of ferromagnetic material by B-H curve. Then, the tangential air-gap flux density is calculated by the SVM and the complex relative air-gap permeance is calculated by the CVCTM to determine the effect of slotting. Finally, the radial and tangential EM force waves are obtained by Maxwell stress tensor method. The proposed semi-analytical method is verified through measuring vibration acceleration of the NSPSG. [ABSTRACT FROM AUTHOR]

This paper proposes a monolayer Halbach array based permanent magnet spherical motor (PMSpM) using cubic permanent magnets (PM). The research aims to provide a fast computing model to calculate the magnetic field for this PMSpM, which helps for future PMSpM optimization and control study. Three thickness equivalence principles are provided and compared for cubic PMs. The magnetic scalar potential is introduced, and the spherical harmonics expansion is implemented for rotor magnetic field analysis. Engineering revision is used to reduce the Legendre function deviation in polar angle direction. Torques and forces are deduced using the Lorentz force law, and relatively simple models of this PMSpM for both magnetic fields and torques are acquired. In addition, a prototype motor has been developed, and the analytic results of air-gap flux density and torque are compared with their finite element simulation and experimental results, which are proved consistent. It is concluded that the fundamental component of the spherical harmonics can be used to present the magnetic field model, which uses fewer integrals than the Biot-Savart law based solution, and the modeling results of the magnetic field flux density, forces and torques are in line with the expectations. The analytic models are proved correct. [ABSTRACT FROM AUTHOR]

This work presents a novel speed sensor less air‐gap flux‐oriented vector control of dual stator induction generator (DSIG) used for grid connected, variable speed wind energy generation system. The DSIG consists of two stator windings electrically separated by an angle of 30° with dissimilar pole numbers, which are in the ratio of 1:3. This arrangement offers reduced magnetic core saturation and less harmonics in stator currents, which results into reduced stator winding losses. Moreover, presence of two stator windings makes DSIG suitable to be used in high power application. In conventional rotor‐flux‐oriented control, the rotor flux is oriented along the d‐axis of the rotor winding. But the rotor flux is not easily accessible. Air‐gap flux‐oriented vector control (AGFOVC) is advantageous as compared to conventional vector control because the air‐gap flux is easily accessible and does not require any special arrangement for the measurement of variables. Moreover incorporation of this novel speed sensor less air‐gap flux‐oriented vector control also eliminates the use of speed encoder as the rotor speed is estimated from the machine terminal variables. Elimination of speed encoder not only reduces the cost of the overall system but also nullifies the error due to mismeasurement of speed and enhances control flexibility and robustness. As a result of which robustness of the system increases. Here, two separate converters are used for the two stator windings of the machine. And the converter switching's are being performed by space vector‐based novel dwell time optimized 13‐zone hybrid PWM. This special PWM results in better harmonic performance, reduced torque pulsation, and minimal switching loss. The simulation of the overall system is performed in MATLAB environment and the simulated results are validated experimentally using dSPACE controller board DS1104. Close proximity in simulated and experimental waveforms justifies the effectiveness of the proposed work. [ABSTRACT FROM AUTHOR]

This article investigates the influence of stator slot number on electromagnetic performance of two-pole high speed permanent magnet (HSPM) slotted motors with toroidal (TO) windings. Four two-pole slotted motors with different slot numbers, i.e., 3, 6, 9, and 12, are globally optimised for maximum torque, and their electromagnetic performance are compared, including winding factor, air-gap flux density, back electromotive force, cogging torque, electromagnetic torque, winding inductances, unbalanced magnetic force (UMF), and various loss components. It shows that the six-slot/two-pole HSPM motor with TO windings is eminently suitable for high speed application due to no UMF and easy to realise a modular structure. In addition, TO and tooth-coil windings are compared in the three-slot/two-pole motors, and the results confirm that TO windings are not suitable for use in the three-slot/two-pole HSPM slotted motor due to large airgap field harmonics. Finally, a six-slot/two-pole prototype motor is manufactured and tested to validate the finite element predictions. [ABSTRACT FROM AUTHOR]

In order to overcome the disadvantages of 12/8 pole bearingless switched reluctance motors (BSRMs), such as high commutation frequency, more stator windings, and more power devices, a 6/4 pole BSRM with half the commutation frequency and number of windings is studied. The structure characteristics and operation characteristics of the 6/4 pole BSRM are investigated through modeling, simulation, and prototype experiment, and the main performance indices, such as suspension force, inductance performance, and air-gap flux density, are evaluated to reveal the levitation control mechanism of the 6/4 pole BSRM with permanent magnets in its stator yoke. The motor can suspend stably in the radial direction, and the correctness and feasibility of the theoretical analysis are verified. [ABSTRACT FROM AUTHOR]

Large medium-voltage electric machine stators are usually equipped with form wound coils made of flat conductors (strands) and embedded in open (rectangular) slots. Air-gap magnetic flux lines can enter the slot and, sweeping the strands placed nearest the slot opening, induce eddy currents in them. Such eddy currents cause additional losses which can be much higher than usual skin-effect and proximity losses. In order to avoid dangerous overheating and hot spots, the additional losses in question need to be carefully predicted in the design stage. Time-stepping finite-element analysis (TSFEA) can be used for the purpose, which however implies a large computational burden and requires the machine geometry to be modeled in detail. This article proposes alternative methods based on time-harmonic finite-element analysis (THFEA) simulations performed on highly simplified machine models and with no need to take rotor motion into account. The proposed methods are shown to produce very accurate results, compared to TSFEA, but with very significant time and computational savings. [ABSTRACT FROM AUTHOR]

The open phase fault is much specified in three--phase squirrel cage induction motors. However, this defect develops an unsymmetrical magnetism generates noise and vibration in the motor. Finite Element Method (FEM) is the most accurate technique to analyze the induction motor, because it can include all actual characteristics of both healthy and faulty conditions. In this paper, an FEM to analyze a 2.2 (kW) three--phase squirrel cage induction motor with the open phase fault is proposed. An experimental investigation to display the stator current waveforms with healthy and faulty conditions are obtained and compared under different load operations. The currents obtained are introduced into FEM analysis, which is used for magnetic field calculation and the magnetic flux density in the air-gap, stator teeth and in the stator yoke for both healthy and faulty operations. [ABSTRACT FROM AUTHOR]

In this article, a process for reducing the electromagnetic vibration and noise by changing the shape of the stator is presented. Although the fundamental wave of the air gap magnetic flux density contributes to the average torque of the motor, other spatial harmonics which were except the fundamental wave of that cause vibration and enfeeble the output of the motor. Therefore, it is important to reduce the spatial harmonics for performance of the motor. Through the proposed process, it is possible to obtain an objective function to reduce the specific harmonics by assigning weights to each spatial harmonic. The reduction in the fundamental wave is minimized and it is possible to reduce the spatial harmonics that have an adverse impact on vibration. After the process, a model can be found that maintains the electromagnetic performance as much as possible while optimally reducing the vibration. To verify the process, the electromagnetic vibrations by a radial force of the proposed and conventional models were compared, and it was confirmed that the electromagnetic vibration of the proposed model was reduced. The validity of the analysis was proved through finite-element analysis. [ABSTRACT FROM AUTHOR]

This article presents two novel double-layer permanent-magnet flux reversal (PMFR) machines to improve the torque capability, namely Machine A and Machine B. Both the Machine A and Machine B are designed as the consequent-pole PMFR machines. The rotors of two machines are identical, which adopt Halbach array permanent-magnet (PM) in the rotor slot to guide the flux into the rotor teeth to reduce the leakage flux. However, the PM relative positions of two PMFR machines on the adjacent stator teeth are different, which result in different pole numbers of air-gap flux density. The operation principles and performances of two machines are introduced and compared in this article. In addition, the air gap fields of two machines by PM magnetomotive force (MMF) are analyzed and the contribution of the dominant air-gap flux density harmonics to torque is revealed. [ABSTRACT FROM AUTHOR]

There is only slot frequency electromagnetic vibration and no pole frequency vibration in rotating armature permanent magnet motor (RAPMM), which is the advantage of this motor. The open of slot makes the air-gap magnetic field distorted and causes the harmonic of electromagnetic excitation force. In order to reduce the slot frequency vibration of the RAPMM, the method of placing magnetic slot wedge (MSW) at the slot opening is put forward accordingly. Through the finite-element simulation, it is finally shown that the MSW is capable of weakening the harmonic of the air-gap flux density, as well as decreasing the high-frequency component of the electromagnetic excitation force. Therefore, it is acknowledged that MSW can suppress the cogging torque and the vibration of corresponding frequency on the stator significantly. Finally, it is confirmed by the experiments that the built-in MSW is an effective measure for reducing the vibration of the RAPMM. [ABSTRACT FROM AUTHOR]

In a squirrel-cage induction motor, because the rotor windings are assembled from conductor bars short-circuited by end rings, the number of poles is not an intrinsic characteristic of the windings, as it occurs in the case of wound rotor windings, but it is a consequence of the distribution of the currents induced in the bars. However, since the motor works, the number of stator and rotor poles must necessarily be the same, and the explanation of why this occurs is usually left to physical considerations. The paper proposes the analytical proof that in a squirrel-cage induction motor, the number of rotor poles is the same as that of the stator. The proposed demonstration is based on the determination of the air gap flux density distribution generated by any set of currents circulating in the rotor bars, without any hypothesis about their waveform. The distribution is expressed as sum of infinite space harmonics, for each of which a current space vector can be defined. First, the special case of sinusoidal stator currents is addressed, and then the general one of stator currents having any waveform. In this way, it is possible to show that the only nonzero rotor current space vector is the one corresponding to the space harmonic having a number of poles as that of the stator. [ABSTRACT FROM AUTHOR]

This article presents a new field-modulation double-stator electrical-excitation synchronous machine (FM-DSEESM) and analyzes its harmonic components of double-layer air gap magnetic field. The key is that both the types and sources of various harmonic-components of air gap magnetic field are derived by taking into account the permeance components of both inner and outer stator teeth and modulation-ring rotor. The selection criteria of main working harmonic components of excitation field is clarified to achieve the armature-winding configuration. Then, the working harmonic components of air gap magnetic field, which have the same pole pairs, rotating direction, and rotating speed, respectively, can be figured out by comparing the mathematical derivation and finite-element analysis results from the excitation field and armature reaction magnetic field. By analyzing the contributions of the air gap flux density components to the electromagnetic torque, it is found that the electromagnetic torque of the proposed FM-DSEESM mainly consists of two parts, namely the reluctance torque components generated by the stationary working harmonic components and the armature reaction torque components provided by the rotating working harmonic components. A low-speed direct-drive FM-DSEESM prototype is fabricated to verify the validity of the proposed analysis approach. [ABSTRACT FROM AUTHOR]

Dual stator winding induction machines (DSWIMs), which have two sets of three-phase windings with unequal pole pairs in their stator and a standard squirrel cage rotor, have overcame the narrow speed operation region and circulating current problems exists in other types of dual winding machines. These advantages are resulted from the independent operation of their winding sets. The independent operation of winding sets will be guaranteed if the flux saturation is avoided. This letter proposes a novel reference frame angle determination technique that not only guarantees the flux saturation avoidance but also results in flux optimization in DSWIMs. Despite pervious methods, the proposed method does not require position or speed sensor and it is easily applicable in various control schemes and in different reference frames. This method is implemented in a flux and torque vector control system for driving a 3.3 kW DSWIM. The experimental results confirm the effectiveness of the proposed method. Moreover, by implementing the proposed method, the torque sharing between the two winding sets is properly done according to the power rating of each of them. [ABSTRACT FROM AUTHOR]

Determining the stator slot design parameters of the alternator has a great importance to provide the desired magnetic flux distribution for a permanent magnet generator (PMG). The objective of this article was to investigate the optimum design parameters of PMG slot design for small-scale low-speed wind turbine generator by using the design of experiment techniques. The Maxwell simulations have been used for numerical experiments on geometric design variables of stator slots (Bs0, Bs1, Bs2, and Hs2) in order to evaluate the coefficients of second-order models for the responses. Efficiency, stator teeth flux density, stator yoke flux density, and air-gap flux density are determined as the responses that have to be optimized. A gradient search was used for optimization. The solution of this design problem shows how the experimental design method can be combined with the numerical simulation and how this approach is well adapted to the optimization process. As a result, the efficiency of the PMG is improved under the desired magnetic flux conditions. [ABSTRACT FROM AUTHOR]

This study analyses a double Y shaft 30° winding for six-phase fault-tolerant permanent magnet synchronous motors and introduces a novel modular 18-slot stator topology used in high-performance electric vehicles with unequal teeth width and unequal slot size. The new topology adopts double-layer winding in the same phase and single-layer winding in the adjacent phase. Additionally, two new pole/slot combinations for the six-phase motor, 18-slot/10-pole and 18-slot/14-pole, are proposed by analysing the air-gap flux harmonics that are produced by the stator winding. In addition, the optimal design of the 18-slot/10-pole motor is determined by using the average torque and the torque ripple as indexes. The motor can run continuously in the range of 0–4 times the rated speed with a one-time short-circuit current, a high isolation capability in the different phases and a high efficiency. The final parameters and performance of the 18-slot/10-pole motor are provided. [ABSTRACT FROM AUTHOR]

For the five-phase permanent magnet (PM) machines with conventional Halbach array rotor, although the third harmonic current is injected into the phase current, the torque density hardly increases due to the absence of the third harmonic air gap flux density. Hence, a Halbach array considering third harmonic air gap flux density is proposed in this paper, and the topology is described and compared with the conventional Halbach array. The magnetizing angle of the proposed Halbach array and the stator teeth width are optimized based on the nonlinear programing method. The electromagnetic performances of the five-phase PM machines with the proposed Halbach array, including open-circuit flux density, back electromotive force, flux density under the rated load, cogging torque, average torque, torque ripple, loss, and efficiency, are compared with the PM machine with conventional Halbach array by finite-element method. It is demonstrated that the torque density and efficiency of the PM machine with the proposed Halbach array are higher than that of the PM machine with conventional Halbach array. Finally, the five-phase 10-slot/8-pole PM machines with proposed Halbach array is manufactured and tested to verify the analysis. [ABSTRACT FROM AUTHOR]

The stator–rotor slot combination is an important parameter in the design of high-voltage induction motor (HVIM). The different design of the stator–rotor slot combination will have an effect on the performance of the HVIM, such as torque, air-gap flux density, loss and so on. In order to analyze its influence, 10 kV, 1000 kW HVIM is taken as an example and the finite element model is established. The correctness of the model is verified by experiments. Firstly, based on the finite element method, the electromagnetic field of HVIM with different rotor slots is solved, and performance parameters of the HVIM are obtained. Based on these parameters, the air-gap magnetic density, overload capacity, average torque and torque ripple of the HVIM are studied, and the distribution rules under the different number of rotor slots are obtained. In addition, the difference of stator core loss and rotor eddy current loss of different rotor slots is analyzed, and the variation mechanism of loss change is revealed. Finally, the performance parameters of the HVIM with different rotor slots are compared, and the reasonable number of rotor slots is obtained. The conclusion of this paper provides reliable theoretical guidance for improving motor performance. [ABSTRACT FROM AUTHOR]

Braking torque is the most important performance parameter for a permanent magnet retarder used in heavy vehicles. This paper proposes a model of the permanent magnet retarder for braking torque at different speeds considering the skin effect, the magnetic leakage, and the actual path of the eddy currents. Based on the magnetic equivalent circuit and the piecewise function method, the static and the transient air-gap flux density models are established, and their accuracy is verified by comparison to the finite element method (FEM). The permeability distribution curve of the retarder stator is obtained by a simple permeability-measuring instrument, considering the skin effect on the permeability of the stator. Thus, the effective permeability function of the stator is obtained at different rotational speeds, and the transient air-gap flux density model is optimized using the effective permeability function. The simulation results showed that the optimized transient air-gap flux density of the calculation model was in good agreement with the FEM. Finally, the calculation model of the eddy current braking torque was verified by the bench test. [ABSTRACT FROM AUTHOR]

A novel hybrid excited asymmetric stator pole doubly salient machine (HEASPDSM) is proposed in this paper. The new topologies and operational principle are first investigated by using a simplified equivalent magnetic circuit model. The harmonic components of air-gap flux density are then analyzed. The influence of key structural parameters of the proposed machine on the flux regulation ability and torque is studied. A full comparison on main electromagnetic performance indexes of the proposed 12/7 (stator/rotor poles) HEASPDSPM and several traditional doubly salient machines is presented. A prototype is fabricated and tested to validate the theoretical analysis. The results well demonstrate that the HEASPDSPM possesses various merits, such as strong flux regulation capability, high torque density, low cogging torque, and low torque ripple. [ABSTRACT FROM AUTHOR]

In this paper, by solving the Maxwell's equations, an analytical model is developed for the prediction of the air gap flux density in the eccentric permanent magnet (PM)-inset machines at no-load and on-load conditions. Since in this model neither Schwartz–Christoffel transformation nor perturbation analysis is used, it is fast and accurate. In the modeling process, the stator of the eccentric machine is replaced with an equivalent surface current (ESC), which is injected at the stator bore. Distribution of the ESC is unknown and must be selected, such that the resultant tangential field satisfies the boundary condition at the stator bore contour. To apply this condition, the flux density of the PMs, armature current, and the ESC are obtained by applying the subdomain analysis and using a conformal transformation. The armature current and ESC are considered as a surface current sheet at the stator bore. The back electromotive force and inductances of the eccentric machine are obtained in the proposed model. In addition, using the Maxwell stress tensor, the unbalanced magnetic force, and the electromagnetic torque are computed. Finally, the model is verified by means of finite element analysis. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this paper, the influence of stator teeth number on permanent magnet (PM) field couplings of co-axial dual-mechanical-port flux-switching permanent magnet (CADMP-FSPM) machines for fuel-based extended-range electric vehicles is investigated. First, the relationships between the inner and outer stator teeth numbers are analytically evaluated. Second, four typical structures, including 5/6–12/22, 10/12–12/22, 5/6–18/42, and 10/12–18/42, of CADMP-FSPM machines are analyzed, and three key stator teeth types, namely, series, parallel, and independent teeth, are defined. Third, the PM field coupling levels of four structures, featured by PM field distributions and air-gap flux densities, are compared with stator teeth matchings. The results indicate that the 10/12–12/22 structure exhibits the lowest PM field coupling and the prior open-circuit performance. Furthermore, the PM field coupling effects on the inner and outer air-gap flux densities are analyzed. Finally, a prototyped 10/12–12/22 CADMP-FSPM machine is designed, optimized, and manufactured, and the experimental results verify that the PM field coupling level of the prototype is negligible, which agrees well with the finite-element predictions and the proposed matching criteria for the selection of the inner and outer stator teeth numbers of CADMP-FSPM machines. [ABSTRACT FROM AUTHOR]