Pole Combinations Research Articles

Research on the influence mechanism of assembly stress on reliability of space deployable mechanism

The on-orbit performance of spaceborne SAR satellite mainly depends on the unwrapping precision of antenna panel, which is determined by its supporting pole system. The assembly stress of the pole system affects the antenna deployable precision in the assembly process of SAR antenna deployable mechanism. Aiming at this problem, this work presents a efficient method that the three-dimensional model of the deployment mechanism of SAR antenna is established, and the method of finite element simulation analysis is adopted. Prestress is applied to the pole system to simulate its assembly stress, and then we study the deformation law of the antenna panel under different assembly stress combinations of the mast system, and the mapping relationship is determined between the mast system and the flatness of the antenna panel. The most sensitive pole affected by the antenna panel deformation is obtained. The results show that the flatness of the antenna panel is related to the dimensional tolerance and position of the pole system, especially Large dimensional tolerance results in large deformation of antenna panel. In addition, the deformation area of antenna panel is determined by the assembly stress of different pole combinations. According to this research, it is concluded that the poles which should be controlled are obtained in the assembly process of the antenna deployable mechanism, which lays a theoretical foundation for the high precision assembly of the truss space deployable mechanism.

Design and Validation of an Unconventional 39-Slot PM Synchronous Motor With Asymmetric and Unbalanced AC Windings

One of the main issues in manufacturing rotors for integer slot surface-mounted permanent magnet (PM) synchronous motors is the rotor skew. Motor manufacturers typically prefer to avoid skewing due to the added complexity and the difficulty in controlling the accuracy of the skewing and achieving the required outcome. This article proposes a design that minimizes torque ripple without using any kind of skewing in the rotor using asymmetric ac windings with unconventional stator slot-pole combinations. First, feasible slot and pole combinations are reviewed for PM synchronous motors. Theory behind unconventional asymmetric and unbalanced ac winding PM motors is presented. A lumped-parameter magnetic equivalent circuit for such unconventional stator is provided for a 1.7-kW PM motor. Detailed 2-D finite element analysis (FEA) is performed and compared with the lumped parameter model. A prototype motor is manufactured, and open-circuit as well as full-load tests are performed. Good agreement between the analytical, FEA, and test results is obtained.

Multi-physics design and analyses of dual rotor synchronous reluctance machine

Dual rotor topology of synchronous reluctance machine is here proposed to improve the motor torque density and reduce the torque ripple. Thus, allowing synchronous reluctance machine to merge into EV and HEV applications. This paper presents a multi-physics design and analyses of three double rotor synchronous reluctance machine, 24/4, 36/4 and 48/4 stator slot/rotor pole combinations, through electromagnetic, mechanical and thermal analysis. First, a genetic algorithm optimization process linked to magnetic FEA has been used. The optimization is set to target the highest torque, lowest torque ripple and core loss. Mechanical study and investigation of the magnetic and rotational forces on the rotor ribs and stator tooth-tip structure have been considered to guarantee the mechanical robustness. Furthermore, the design assembly structure to ease heat dissipation from the stator has been investigated thermally. Finally, a comparison with a conventional single-rotor synchronous reluctance machine having the same size and operating conditions have been made to highlight the advantages of the double rotor synchronous reluctance machine. From the comparison it has been concluded that the double rotor machine produced 45% higher torque and 40% less torque ripple compared to its single rotor counterpart. Synchronous Reluctance Machines, Double Rotor Machine, Structural Analysis, Double Airgap Machines. • The design of a novel double rotor synchronous reluctance machine is presented. • A multi-physics design process and genetic algorithm global optimization are used. • The double rotor machine showed higher power density when compared to the single rotor. • Lower torque ripple is found in the double rotor machine when compared to the single rotor. • The higher power density and lower torque ripple are essential for automotive application.

A Novel Mechanical Flux Weakening Method for Flux Switching Permanent Magnet Machine

— This article presents a novel mechanical field weakening method for flux switching permanent magnet (FSPM) machines to extend the torque-speed characteristic and improve the efficiency at high speeds. The proposed method consists of segmenting the permanent magnets (PMs) part along the back-iron radius into a circular shape embedded into the rectangular magnet. The circular-shaped magnet segments (CMSs) can then be rotated to enhance or short circuit the PMs flux. When the magnetization orientation of the PMs and the CMSs are in the same direction, the flux will flow as of that of the conventional FSPM machine, i.e. field strengthen. Conversely, when the high speed is required, the CMSs will be rotated 180°, and therefore, the PMs and the CMSs magnetization orientation will be in opposite direction, and therefore, a short circuit of the PMs flux will be created. This will lead to lower PMs flux linkage, and therefore, higher field weakening factor. A FSPM machine with 12/10 stator/rotor pole combination has been selected to investigate the proposed method. First, to study the proposed method, a comparison of the electromagnetic performance of the FSPM machine in flux strengthening and weakening states has been conducted and presented. Then, mechanical analysis of the proposed method has been made with focus on the mechanical rotating system and the consequent structural stress on the rotating magnet. In conclusion, the proposed method shown a good field weakening capability and improved torque-speed characteristics.

Effect of Phase Shift on Inductance and Short-Circuit Current in Dual Three-Phase 48-Slot/22-Pole Permanent-Magnet Machines

This article investigates the effects of phase shift on the inductance and short-circuit current (SCC) in permanent-magnet (PM) machines with dual three-phase winding configurations. First, the relationship between the phase shifts and slot/pole combinations, for the dual three-phase winding configurations, is discussed. Second, analytical expressions of the inductance are derived for the 48-slot/22-pole PM machines with different phase shifts based on the winding function theory. Afterwards, the SCC amplitude of different phase shifts is comparatively analyzed. The investigation reveals that the 7.5° and 30° configurations have great significance to improve the self-inductance value. Thereby, the 30° configuration has comparable SCC amplitude compared to the 7.5° counterpart, while being lower than the 15° configuration one. Moreover, the 30° configuration exhibits lower eddy-current loss and preferable torque performance than its counterparts. Furthermore, the finite-element method is used to calculate electromagnetic performances for evaluation. Finally, some experiments on the prototype machine are carried out for validation.

Research on Stator Slot and Rotor Pole Combination and Pole Arc Coefficient in a Surface-Mounted Permanent Magnet Machine by the Finite Element Method

A surface-mounted permanent magnet (SPM) machine is widely used in many auxiliary parts of an electric vehicle, so its design level directly influences the performance of the electric vehicle. In the design process of the SPM machine, selecting the appropriate stator slot and rotor pole combination and pole arc coefficient is a necessary and important step. Therefore, in this paper, a 750 W machine is set as an example to research stator slot and rotor pole combinations and pole arc coefficients for the SPM machine. First, the design schemes of machines adopting different stator slot and rotor pole combinations are determined according to the winding coefficient, stator size, and electromagnetic performance requirements. Further, finite element models of SPM machines with different stator slot and rotor pole combinations are established by Ansys Maxwell. On this basis, the back electromotive force (back EMF), cogging torque, electromagnetic torque, and loss and efficiency of SPM machines are calculated and compared to select the better stator slot and rotor pole combinations. Further, effects of pole arc coefficient on cogging torque and electromagnetic torque are also researched to guide the selection of the pole arc coefficient in the design process of the SPM machine. Conclusions achieved in this paper will provide guidance for design of the SPM machine.

Phase Shift Technique to Improve Torque of Synchronous Reluctance Machines With Dual M-Phase Windings

This article proposes a torque improvement method for dual <i>m</i>-phase synchronous reluctance machines by phase shift technique. The emphasis is put on the relationship of <i>d</i>&#x2013;<i>q</i> axis inductance harmonics and phase shifts. First, all feasible phase shifts for various slot&#x002F;pole combinations are discussed in general. Second, the influences of phase shift on reluctance torque performance are investigated based on inductance analysis. It is founded that the first main torque harmonic can be eliminated when phase shift equals to <i>&#x03C0;</i>&#x002F;2<i>m</i> (<i>m</i> is odd) and <i>&#x03C0;</i>&#x002F;<i>m</i> (<i>m</i> is even), respectively. This is the optimal phase shift covering all the <i>m</i> cases. Third, the optimal phase shift with torque improvement and ripple reduction is verified by the theoretical analysis and finite element method. Finally, the dual 3-phase 24-slot&#x002F;10-pole synchronous reluctance machines with 30&#x00B0; and 60&#x00B0; phase shifts are fabricated. The experiments on the prototype machine are carried out for validation.

Comparative Research on Four-Phase Dual Armature-Winding Wound-Field Doubly Salient Generator With Distributed Field Magnetomotive Forces for High-Reliability Application

In this article, a four-phase dual armature-winding wound-field doubly salient machine with distributed field magnetomotive forces (DAW-WFDSM-DF) and corresponding double-redundant rectifier circuit are proposed to improve the electromagnetic performance of the traditional WFDSM in terms of the output voltage ripple, fault-tolerant capability and output capability. Firstly, due to the uniformly distributed field magnetomotive forces of the proposed machine, the more feasible stator/rotor pole combinations of the four-phase machine can be obtained and the influence of stator/rotor-pole combination on electromagnetic performance is investigated, especially for the fault-tolerant capability. Based on a multi-objective evaluation function including output capability, fault-tolerant capability and unbalanced magnetic forces, the $4N$ -stator-pole/ $3N$ -rotor-pole ( $4N/3N)$ and $4N/5N$ combinations are recommended. Then, considering that the fault-tolerant capability of 8/6-pole machine is poorer than that of 12/9-pole one, the 12/9-pole and 8/10-pole DAW-WFDSM-DFs are comparatively researched for taking as the representatives of $4N/3N$ and $4N/5N$ , including no-load and on-load characteristics and fault-tolerance performance under single winding open-circuit condition. Finally, as the 8/10-pole DAW-WFDSM-DF exhibits remarkably higher efficiency and stronger fault-tolerant capability than the 12/9-pole one, an 8/10-pole prototype is manufactured and tested to verify the analytical results.

Characteristic analysis of flux switching PM machine with various pole and slot combinations

This paper examines the influence of pole and slot combinations on the electromagnetic performance of the flux-switching permanent magnet (FSPMs) machine. For this purpose, first the production of air gap flux density in machine analytically discussed. Next, five different pole and slot combination are selected by using the knowledge of air-gap flux density expression. The performances of the different combinations are analyzed and compared using the finite element analysis (FEA), and optimal pole and slot combination is suggested. It is found that the pole and slot combination has a dominant effect on machine performance and needs to be considered during the design stage.

Investigation of Double-Side Field Modulation Mechanism in Consequent-Pole PM Machines With Concentrated Windings

In this article, the field modulation effect (FME) of consequent-pole permanent magnet (CPM) machine is revealed and investigated from the perspective of a double-side slotting effect (DSSE), which can characterize and elaborate its torque production mechanism. Since the CPM machine features that both PM and armature fields are modulated by stator /rotor teeth, which generates more field harmonics contributing to the torque production compared with conventional surface-mounted PM (SPM) machine. A simplified PM magneto-motive force (MMF)-permeance based model is first established to confirm the effective working harmonics of the CPM machine. The contributions of dominant air-gap field harmonics to the torque production are then demonstrated and quantified based on Maxwell stress tensor (MST) method. The impacts of FME on the torque performance of the CPM machines with different stator-slot/rotor pole combinations are subsequently investigated by the finite element (FE) method and compared with those of conventional SPM counterparts. Besides, the influences of rotor PM parameters on the FME of the CPM machine are also evaluated. Finally, the experimental measurements on a 12-slot/14-pole CPM machine prototype are carried out to validate the theoretical and FE analyses.

Development and Investigation of Novel Axial-Field Dual-Rotor Segmented Switched Reluctance Machine

This article presents a new type of axial-field switched reluctance machine (AFSRM) and axial-field dual-rotor segmented switched reluctance machine (ADS-SRM), along with its design methodology. The proposed ADS-SRM is featured by the segmental stator and rotor poles, the auxiliary flux-conductive rings, and the concentrated windings. The yokeless topology reduces the active length of the motor. Besides, the adopted short-end winding layout increases the slot-fill factor and the motor's reliability. First, the basic topology of ADS-SRM is introduced along with its operating principle and various stator/rotor pole combinations. The three-phase 12/8 configuration of ADS-SRM is chosen for further analysis. Then, the design methodology considering the fringing and leakage field effects through the magnetic equivalent circuit (MEC) method is developed, and the flowchart detailing the design procedure is presented. Through the comparison with the conventional yokeless and segmented armature (YASA) topology, ADS-SRM exhibits excellent performance at overload conditions. The prototype is designed and fabricated, and the experimental results verify the motor performance.

Design and fabrication of an outer rotor permanent magnet synchronous generator with fractional winding for micro‐wind turbines

Permanent magnet synchronous generators (PMSGs) have been widely used in micro-wind turbines (MWTs) for direct-drive applications. The generating maximum power from the PMSGs used in the MWTs is desired. However, cogging torque (CT) and design form of the PMSGs prevent this. Therefore, various methods are applied to reduce the CT of PMSGs in the literature. Some of them are inapplicable and some are the ones that cause power loss. In this study, to overcome the expressed causes, a new design, fabrication, and application of an outer rotor PMSG with fractional winding having a slot–pole combination technique for MWTs have been suggested, designed, and implemented on an MWT. As a result of the new design combination of ±1 or ±2 between the numbers of stator slot (N S) and the number of pole-pairs (2p), the ratio of the CT value to the nominal torque value in the new prototyped outer rotor PMSG was found as 6.25%. Finally, the operating power can generate 1029 W through the prototype PMSG with fractional winding having a slot–pole combination technique integrated into the direct-drive MWT system.

Partitioned Stator Switched Flux Machine: Novel Winding Configurations

Torque density is one of the major limiting factors in machine design. In this paper, we propose the hybrid excited partitioned stator switched flux machine3 (HE-PSSFM3). In HE-PSSFM3, armature winding is positioned on the outer stator whereas the permanent magnet (PM) and field winding are placed at the inner stator, while the rotor is free from excitation sources and armature winding. Moreover, concentrated field winding is replaced by toroidal winding. The power splitting ratio between two stators/rotor pole combinations is analytically optimized and are validated through genetic algorithm (GA) in order to enhance average torque and flux regulation capability. The electromagnetic characteristics of the improved and initial design are evaluated and compared with existing designs, i.e., HE-PSSFM1 and HE-PSSFM2. The proposed HE-PSSFM3 has achieved high average torque, i.e., 2.0015 Nm, at same armature and field current densities of 5 A/mm. The results show that the average torques of the proposed design are 35% and 15% greater than HE-PSSFM1 and HE-PSSFM2, respectively. Furthermore, the analysis of various parameters such as flux linkage, flux regulation, electromagnetic performances, cogging torque, back EMF, electromagnetic torque, and torque ripples are investigated using two dimensional (2D) finite element analysis (FEA). Moreover, the simulation results of the proposed design are validated through GA and analytical modeling.

Levitation Force Improvement by Effective Magnetic Interaction in Two Magnetic Levitation Systems With HTS Coil and Bulks

In this article, we studied a magnetic levitation system which was composed of a high-temperature superconducting (HTS) coil, HTS bulks, and a ferromagnetic material (rail). We set two magnetic levitation systems in one ferromagnetic rail. We analyzed the levitation force depending on changing the distance between HTS coils of each direction of current flowing. As a result of comparing two poles that has current flowing through its coils in one direction and two poles that has current flowing through its coils in different directions, the model which had the coils in one direction was better. A reason for this result is discussed comparing with the magnetic flux density and the stress tensor in a ferromagnetic rail. In addition, the distance between coils was also important for the magnetic interaction. We show the tendency of levitation force obtained by changing the distance between coils in each direction of current flowing and explain the reason. In this article, it is found that a greater force can be obtained by using magnetic field interaction effectively. We optimized arrangement and magnetic pole combination and we succeeded to improve the levitation property.

Feasible Stator/Rotor Pole Combinations of Variable Flux Reluctance Machines With Second Harmonic Current Injection Method

The second harmonic current injection method is recently developed to enhance the torque density of variable flux reluctance machines (VFRMs). This article investigates the feasibility and effectiveness of the second harmonic current injection method in VFRMs with different stator/rotor pole combinations. By using magnetic gearing effect, it is found that the second harmonic injection method can only be applied to the 6 j /(6 i ± 2) j ( i , j = 0, 1, 2…) stator/rotor pole VFRMs for the torque density enhancement. For the other stator/rotor pole combinations, the second harmonic current has no contribution in average torque production but only leads to excessive torque ripple. Further, by using global optimization method and finite element analysis, 6/8 stator/rotor pole combination is proved to be the optimal stator/rotor pole combination for 6-stator-slots VFRMs with the second harmonic current injection method, being able to exceed the maximal torque density of conventional VFRMs by 12% at a fixed copper loss.

Design, analysis, and fabrication of a direct drive permanent NdFeB magnet synchronous motor for precision position control

Direct drive motors have the excellent ability for precision position control due to their direct connection to load and elimination of the gearbox and pulley backlash. Among the direct drive motors, permanent NdFeB magnet synchronous motors (PMSMs) are the best choice for control systems due to their high efficiency, high power density, good dynamic behaviour, and excellent controllability. This study deals with the design, analysis, and fabrication of a direct drive PMSM for precision position control. To reach this aim, the designed motor should have very low cogging torque and torque ripple to avoid the motor deviation at the target point. To achieve these purposes, at first, a suitable combination of slot and pole has been selected for the motor and then the optimum shape of the magnets has been obtained by using the 2D finite element method. For the magnet shape, two important parameters of the magnet are optimised simultaneously. The designed motor has been fabricated and tested. Both simulation and experimental results show that the designed motor has a very good performance as the point of cogging torque and torque ripple views. Also, the experimental results validate the theoretical calculations.

Research on weakening measure of radial electromagnetic force waves in permanent magnet synchronous motors by inserting auxiliary slots

The accurate calculation and analysis of electromagnetic force waves are especially crucial for comprehensively predicting and weakening the electromagnetic vibration of electrical machines. In this study, a fast and accurate calculation method of radial electromagnetic force density of surface-mounted permanent magnet synchronous motor (PMSM) is presented, the radial electromagnetic force density including amplitude, frequency and order is obtained and the accuracy is verified. Comprehensively considering that the effects of the auxiliary slots on cogging torque and torque ripple, the weakening measure of radial electromagnetic force waves by inserting auxiliary slots is research, and the optimal determinations of the number and the structural parameters of auxiliary slots in PMSMs with different slot–pole combinations are summarised, and six PMSMs with 6-pole/36-slot (6p36s), 4p36s, 6p9s, 8p9s, 8p12s and 10p12s are analysed to verify the universality of the conclusions.

Design and analysis of a kind of rotor ironless high torque density machine using Alnico magnet

Conventional non-rare-earth permanent magnet (PM) electrical machine can hardly achieve comparable performance with the neodymium iron boron (NdFeB) machine due to the low coercivity and remanence. To solve this problem, a new kind of electrical machine using only Alnico magnet is proposed in this study. The novel rotor topology eliminates rotor iron core, and thus effectively limits armature reaction and improves torque density. A kind of rapid assessment method for the demagnetisation effect of q current in different slot–pole combinations through magnetomotive force and winding factor is presented and verified by 2D finite-element analysis. The optimisation of critical dimensions is demonstrated, and the trade-off between high PM utilisation and low demagnetisation effect is emphasised. After that, the good torque–current linearity and robust to demagnetisation characteristics of the proposed topology are proved through a comparison with two rare-earth-free machines. Finally, the performance comparison with a manufactured conventional NdFeB machine under the same volume constraints is provided. The result suggests that the proposed machine has a higher power factor, lower eddy-current loss, and rare-earth PM machine comparable torque density.

Principles of Charge Estimation Methods Using High-Frequency Current Transformer Sensors in Partial Discharge Measurements.

This paper describes a simplified model and a generic model of high-frequency current transformer (HFCT) sensors. By analyzing the models, a universal charge estimation method based on the double time integral of the measured voltage is inferred. The method is demonstrated to be valid irrespective of HFCT sensor, assuming that its transfer function can be modelled as a combination of real zeros and poles. This paper describes the mathematical foundation of the method and its particularities when applied to measure nanosecond current pulses. In practice, the applicability of the method is subjected to the characteristics and frequency response of the sensor and the current pulse duration. Therefore, a proposal to use the double time integral or the simple time integral of the measured voltage is described depending upon the sensor response. The procedures used to obtain the respective calibration constants based on the frequency response of the HFCT sensors are explained. Two examples, one using a HFCT sensor with a broadband flat frequency response and another using a HFCT sensor with a non-flat frequency response, are presented.

Efficiency Improvement Strategy for Multiple Operating Points in Doubly Fed Magnetic Geared Motor

The doubly fed magnetic geared motor, which has dual AC windings, can be operated with different frequencies in the inner and outer windings. However, the inner and outer windings have different numbers of pole pairs to meet the pole combination derived by the magnetic gearing effect, and hence undesirable space harmonic components of the magnetic flux are produced at the air gaps. These space harmonics affect the iron losses at each core, and the resultant iron loss and efficiency are varied by the frequencies of the inner and outer windings. Thus, in this paper, first, the effect of the space harmonic components of the air gap magnetic flux density in the inner stator, outer stator, and the modulating pieces is separately investigated. In addition, the iron loss characteristics of each ferromagnetic material are presented according to the frequency combinations in the inner and outer windings. Secondly, the iron loss maps and the efficiency maps according to the frequency conditions of the inner and outer windings are drawn, and the causes of the characteristic differences in each map are analyzed. Thirdly, the frequency control sequence and the roles of the inner and outer windings as the armature and field parts are changed, and the analysis of the iron loss map and efficiency map is repeated. Finally, the results in the inner-armature case and the outer-armature case are compared with each other, and the possibility of improving the overall operating efficiency over the multiple operating points by using the individual frequency control and frequency combination selection is proved.