Pole Combinations Research Articles

Influence of Winding Configurations and Stator/Rotor Pole Combinations on Field Back-EMF Ripple in Switched Flux Hybrid Excited Machines

Similar to armature back electromotive force (armature back-EMF), the back-EMF also exists in the field winding of hybrid excited machines. However, the existence of field back electromotive force (field back-EMF) is harmful to the safe and stable operation of machine systems, e.g., higher losses, lower efficiency, higher torque ripple, and reduced control performance. This paper systematically investigates the influence of armature/field winding configurations together with stator/rotor pole combinations on the field back-EMF ripple in hybrid excited machines with switched-flux stators. The two-dimensional (2D) time-stepping finite element modeling and prototyping experiments are used for the research. The investigated field and armature coil pitches equal to 1, i.e., non-overlapped windings. The influential factors that are investigated in this paper mainly include the number of layers of field/armature windings, the number of field/armature coils, and the stator/rotor pole combinations. The results show that the field back-EMF’s harmonic order and peak-to-peak value are closely associated with field/armature winding configurations and stator/rotor pole combinations under various conditions. Finally, for validation of the results predicted by the finite element method, a prototype machine is built and tested. Overall, non-overlapped double-layer armature and field windings are recommended for the hybrid excited switched flux machines with various stator/rotor pole combinations to realize relatively lower field back-EMF under different conditions.

Research on Performance of Interior Permanent Magnet Synchronous Motor with Fractional Slot Concentrated Winding for Electric Vehicles Applications

The fractional-slot, concentrated-winding, interior permanent magnet synchronous motor (FSCW IPMSM) has advantages, such as reducing motor copper consumption, improving flux-weakening capability, and motor fault tolerance, and has certain development potential in application fields such as electric vehicles. However, fractional-slot concentrated-winding motors often contain rich harmonic components due to their winding characteristics, leading to increased motor losses and back electromotive force harmonics, thereby affecting the efficiency and constant power speed regulation range of the motor. Based on this, this article first uses the winding function method to explore the inductance and saliency ratio of the interior permanent magnet synchronous motor with different slot pole combinations in the fractional-slot concentrated- winding of electric vehicles. Secondly, this article will establish a 2D finite element parameterized model to analyze and compare the performance of fractional-slot concentrated-winding motors with different slot pole combinations, including air gap magnetic density, back electromotive force distortion rate, overload multiple, and torque. The structural parameters of the motor were optimized with the objective of minimizing the torque ripple under the constraint of minimizing the average torque reduction. The motor slot width, permanent magnet angle, and permanent magnet pole arc angle were analyzed and optimized. The simulation results showed that 12 slots and 8 poles were the optimal design schemes, providing a theoretical basis for the selection of slot pole coordination in the fractional-slot concentrated-winding interior permanent magnet synchronous motor for electric vehicles.

Analysis The Effect Of Magnet Structure On The Unbalance Magnetic Pull Of Fractional Slot Number Type In Permanent Magnet Machine

Within this study, the effect of magnet structure on the unbalanced magnetic draw (UMP) of fractional slot number permanent magnet machines (PMMs) was methodically investigated. The literature revealed that fractional slot number PMMs use a variety of magnet structure configurations, including radial, parallel, and hybrid arrangements. Different magnet configurations were discovered to affect the distribution of magnetic flux density, thereby impacting UMP concentrations. The effect of various magnet geometries, including arc, rectangular, and trapezoidal, on UMP was examined. Moreover, the selection of magnet materials, such as ferrite, neodymium-iron-boron, and samarium-cobalt, influenced the magnetic field distribution and UMP characteristics. Due to their particular slot and pole combinations, fractional slot number PMMs were found to be more susceptible to UMP than other PMM varieties. Unbalanced forces caused by UMP resulted in unwanted vibrations, increased noise levels, and possible machine durability issues. Numerous factors influence UMP in fractional slot number PMMs, including the number of slots and poles, the length of the stator-rotor air gap, the magnet pole breadth, and the magnet thickness. The level of UMP was affected by the interaction of these factors with magnet structure configurations.

A study on motor characteristics based on pole-slot combinations

Electric devices called motors, which have a history of 100 years, are the devices that use the most electricity in the world. Therefore, the development of high-efficiency motors leads to efficient power use and carbon neutrality. In motor design, the combination of poles and slots is very important. It affects many characteristics including back electromotive force waveform and magnitude, torque and torque ripple, cogging torque, noise and vibration, and efficiency. The most widely used combination of poles and slots is 8 poles and 12 slots. And recently, 8-pole 9-slots are also attracting attention for their various advantages. This paper compares the characteristics of 8-pole 12 slots and 8-pole 9 slots through computer simulation. And to overcome the weaknesses of 8 poles and 9 slots, a multiple of the pole-slot combination is applied. Finally, the comparative values are verified through an experiment.

Comparative Study of Novel Dual Winding Dual Magnet Flux Modulated Machines with Different Stator/Rotor Pole Combinations

Comparative Study of Novel Dual Winding Dual Magnet Flux Modulated Machines with Different Stator/Rotor Pole Combinations

Slot Pole Combination Analysis of FSCW-PMVM on Magnetic Field Modulation Performance

Slot Pole Combination Analysis of FSCW-PMVM on Magnetic Field Modulation Performance

Design and Optimization of a Pole Changing Flux Switching Permanent Magnet Motor

A flux switching permanent magnet (FSPM) motor is designed and optimized in this paper to achieve high torque density and expanded speed regulation range from a design viewpoint of pole-changing (PC). Based on the field modulation theory, the PM field in the FSPM motor is modulated by the stator and rotor teeth, generating rich harmonics with different pole-pair numbers in the air-gap flux density. By adopting an appropriate slot pole combination, working harmonics with different slot pitch angles are obtained to establish a basis of the PC-FSPM motor. Then, different working harmonics can be used to achieve different energy conversions with different winding configurations, so the PC operation can be performed to realize the high torque and wide speed regulation range by switching the working modes. Based on the field modulation theory, the operation principle of conventional and PC-FSPM motors are analyzed and compared. Then, according to the design principle of the PC-FSPM motor, a 24/22-pole PC-FSPM motor with the E-core is designed and optimized by a multi-level optimization method. Finally, the electromagnetic performances are analyzed by finite element analysis and the test results of the prototype have verified the feasibility of the motor.

A Novel Dual Port Dual Rotor Wound Field Flux Switching Generator With Uniform and Non-Uniform Rotor Poles for Counter-Rotating Wind Power Generation

In this paper, a novel dual port counter rotating dual rotor wound field flux switching generator (DPCRDR-WFFSG) is proposed for direct drive counter rotating wind power generation. Mechanism of gearless and brushless counter rotating operation of DPCRDR-WFFSG is discussed and simplified formulation is opted for possible combination of the rotor poles number <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$(N_r)$</tex-math></inline-formula> . In proposed DPCRDR-WFFSG, dual electrical ports are formed of non-overlapped armature winding having shared toroidal field excitation winding whereas inner and outer rotors act as inner and outer port. These inner and outer port are thoroughly investigated for electromagnetic performance to search out optimum rotor poles combination. The rotor poles combinations are examined under uniform and non-uniform poles and comparatively studied. Based on simplified formulation, various combinations of the rotor pole numbers are searched out and found that under uniform poles operation, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N_r= 10$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N_r = 14$</tex-math></inline-formula> offers comparatively better electromagnetic performance whereas in case of non-uniform rotor poles <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N_r = 10/14$</tex-math></inline-formula> further improves electromagnetic performance. Furthermore, analysis evident that in comparison with the inner port, outer port shows dominant contribution in electromagnetic performance whereas, in comparison with uniform rotor poles, the new approach of adopting non-uniform rotor poles improve electromagnetic performance. It is worth noting that non-uniform rotor poles in inner ports improves efficiency and power factor whereas in outer port, average torque and output power are enhanced. Finally, validity of uniform and non-uniform rotor poles design approach for DPCRDR-WFFSG is verified with four prototype that validated finite element analysis.

Evaluation of Counter-Rotating Dual-Rotor Permanent-Magnet Flux-Switching Machine with Series and Parallel Stator Teeth

In this study, the focus is on the magnetic path formation and its effects on the performance of a counter-rotating dual-rotor permanent-magnet flux-switching machine (CR-DRPMFSM) for direct-drive counter-rotating wind power generation, based on different stator slot and rotor pole combinations. To fully exploit rotor-shaft bore and improve fault-tolerant design, as well as increase torque density, dual-rotor topologies with the capability for dual electrical and dual mechanical ports are investigated. Moreover, the direct-drive counter-rotating wind power generation technique offers a brushless topology, thus reducing maintenance cost and improving energy conversion efficiency compared to single-blade wind turbine systems. Using finite element analysis (FEA), the inherent magnetic coupling of the series and parallel paths shows varied impacts on the electromagnetic performance of four different CR-DRPMFSMs based on the slot/pole combinations (MI to MIV) considered in this study. The key electromagnetic performance indices, such as torque, cogging torque, torque ripple, power factor, and efficiency, show proportionate variation to the coupling level. A comparative analysis shows that MI exhibits higher average torque, lower torque ripples, and high efficiency, reaching 90% with a power factor of 0.6. As an optimal design, an MI test prototype is developed. The experimental test prototype validates the FEA results under no-load and on-load conditions.

RESEARCH THE EFFECT OF THE FRACTIONAL NUMBER SLOTS OF POLE ON WIND TURBINE GENERATION USING THE ENHANCED SPOTTED HYENA OPTIMIZATION ALGORITHM

The design of machines with permanent magnets is actively developing day by day and is often used in wind energy. The main advantages of such variable speed drives are high efficiency, high power density and torque density. When designing a wind generator with two rotors and permanent magnets, it is necessary to solve such a problem as the correct choice of the number of poles and slots to increase efficiency and minimize the cost of the machine. In this work, an improved spotted hyena optimization algorithm is used to obtain the optimal combination of slots and poles. This optimization algorithm makes it possible to obtain the number of fractional slots per pole and evaluate the operating efficiency of a wind generator with a double rotor and ferrite magnets. At the first stage of machine design, various combinations of slots are installed. Next, the optimal combination is selected from various slot-pole combinations, taking into account the Enhanced Spotted Hyena Optimization (ESHO) algorithm, in which a multi-objective function is configured. Accordingly, the multi-objectives are the integration of reverse electromotive force, output torque, gear torque, flux linkage, torque ripple along with losses. Analysis of the results obtained shows that the proposed algorithm for determining the optimal slot combination is more efficient than other slot combinations. It has also been found that the choice of slot and pole combination is critical to the efficient operation of permanent magnet machines.

Force Ripple Reduction of a Fractional Pole Pair Complementary Modularized Variable Reluctance Linear Machine for Long Stroke Application

Variable reluctance linear machine (VRLM), which takes advantages of magnet free, simple structure and low cost, is one of the emerging candidates for long stroke application. However, due to the abundant harmonics in the air gap, the conventional modular linear machine suffered from thrust ripple which leads to vibration and acoustic noise problem. The thrust force ripple in VRLM is mainly caused by higher-order harmonics in the induced voltage and detent force. To furtherly suppress the odd-order harmonics in the induced voltage and detent force, a fractional pole- pair unequal module arrangement (FP-UMA) design, in which the distances of adjacent modularized mover segments are not equal, is proposed to VRLM and collaborated with complementary structure in this paper. The key is that the modularized movers are artificially designed to be unequally distributed regarding to spatial distribution to eliminate the odd-order harmonics in the induced voltage along with the thrust ripples they caused based on the quantitative analysis on the thrust ripple components. It is revealed that, with the proposed FP-UMA design, the thrust ripple ratio of the machine has been effectively relieved from 4.6% to 2.2% under copper loss of 450W. Further, some design guidelines for the proposed machine, such as position offset of modularized mover Δμ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m2</sub> , DC loss ratio <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> and slot pole combinations are discussed. In addition, the feasibility of the proposed design method is evaluated by finite element method as well as experiments.

Design and Analysis of a Field-Modulated PM Transverse Flux Linear Generator With Tilted Translator

Over the past two decades, linear generators have been widely used in direct drive wave energy converters (DD-WECs), thus simplifying the system structure and improving conversion efficiency. While these linear generators are desirable for wave energy converter because of their high reliability, they must be very large to generate significant electrical power from such low-speed motion. These linear generators have demerits of large volume, low power density and low conversion efficiency when they are adopted in DD-WEC. Magnetically geared machine and field-modulated permanent magnet linear generator can significantly decreases the volume and cost of the required generator, also the speed of travelling magnetic field is enhanced and high power density capability is ensured by the ‘magnetic gearing effect’. A field-modulated PM transverse flux linear generator (FM-PMTFLG) is proposed and analyzed in this paper. The field modulation mechanism in FM-PMTFLG with tilted translator is introduced in detail. The electromagnetic characteristics of different combinations of stator slots and translator poles and different tilt angle of magnetic tilted bars and nonmagnetic tilted bars are comparatively investigated. The FM-PMTFLG prototype is manufactured to validate the results of the selected design parameters and the relationship between magnetic gearing effect and tilted translator. A fundamental experiment was conducted. A good agreement between 3D-FEA and experiment results proved the validity of the generator design.

Comparative study of next generation sequencing and immunohistochemistry on molecular classification of endometrial carcinoma

Objective: To investigate the differences in molecular classification of endometrial carcinoma (EC) between various technical methods and to explore molecular classification schemes suitable for Chinese population. Methods: The study used a comprehensive scheme of next generation sequencing (NGS) and immunohistochemistry for molecular classification of 254 EC cases that were obtained at Department of Pathology, Obstetrics and Gynecology Hospital of Fudan University, Shanghai, China from April 2021 to March 2022. According to the recommended threshold of Sanger sequencing which was approximate-20% variant allele fraction (VAF), NGS data were extracted to simulate the results of Sanger sequencing. Results: The 254 EC patients had a mean age of 51 years (range, 24 to 89 years). Combination of POLE (9-14 exons), TP53 total exons and microsatellite instability (MSI) detection was a better single scheme than NGS alone, while combination of MSI fragment analysis and conventional immunohistochemistry was the best solution and seemed best aligned with TCGA data and recent studies. POLE ultramuted type, mismatch repair defect type, TP53 mutant type and non-specific molecular characteristic type accounted for 11.4% (29/254), 31.5% (80/254), 22.4% (57/254) and 34.6% (88/254) of the cases, respectively. If Sanger sequencing was adopted for POLE and TP53 detection, the frequencies of these EC types were 9.1% (23/254), 31.5% (80/254), 12.9% (33/254) and 46.6% (118/254), respectively, with greatly increasing non-specific molecular characteristics cases. If POLE was detected by Sanger sequencing and others by immunohistochemistry, they were 9.1% (23/254), 42.2% (92/218), 13.8% (35/254) and 40.9% (105/254), respectively, with increasing the false positive rates of the mismatch repair defect group. Conclusions: Small and medium-sized NGS panels with MSI detection is a better solution than NGS alone. Sanger sequencing is currently available for POLE mutation detection, which is not sensitive enough for TP53 mutation detection, and seems equivalent to the efficiency of TP53 by immunohistochemistry. Further optimization of small and medium-sized NGS panels covering MSI detection and POLE and TP53 full exons may be the best choice for the future to meet national conditions.

Topology Development and Performance Analysis of a Dual-Stator Permanent Magnet Arc Motor

In this paper, a dual-stator permanent magnet (PM) arc motor (DS-PMAM) with improved torque density is investigated for some specific direct-drive applications. The proposed DS-PMAM can be considered as the combination of the PM arc motor and the stator-PM motor. Benefiting from two different stator structure, two sets of armature windings are employed to improve the inner space utilization ratio and torque densities. The motor structure and working principle of the DS-PMAM are firstly introduced. The simplified analytical model is derived to provide a solid theoretical guidance for optimization design parameters selection. Then, the design considerations including the slot/rotor pole combination, the armature winding design, and the key structural parameters analysis are carried out to obtain the optimal motor performances of the DS-PMAM. After that, the electromagnetic characteristics of the DS-PMAM are evaluated together with the comparison with the inner-rotor PMAM, the outer-rotor PMAM, the surface-mounted PM PMAM, and the DS flux reversal PMAM. Finally, a prototype is manufactured and fully tested. Relevant experimental results verify the correctness of the FE analysis and the feasibility of this proposed design.

A Novel Parallel-Excited Dual-PM Reluctance Machine With Enhanced Torque and Efficiency Performance

This paper presents a novel parallel-excited dual-PM reluctance machine (DPM-RM) with enhanced torque and efficiency performance. The key is to build an integrated magnetic field with two sets of PM excitation sources in both stator yoke and slot openings. Two excitation sources produce a parallel magnetic field, which contributes to a superimposed magnetic flux in the airgap, thus leading to strengthened flux variation, improved back-EMF and torque. Additionally, with a special slot&#x002F;pole combination, biased component and even order harmonics in the phase magnetic flux are eliminated to make the phase flux linkage more sinusoidal. In the meantime, self-inductance variation is greatly suppressed with odd order harmonics of self-inductance removed, resulting in suppressed torque ripple. The prototype is manufactured, and experiments are carried out to verify the effectiveness of the machine design.

Analysis of Back EMF Harmonics Influenced by Slot–Pole Combinations in Permanent Magnet Vernier In-Wheel Motors

This paper analyzes the back-EMF harmonic characteristics influenced by the slot-pole combinations in permanent magnet vernier motors (PMVM) for in-wheel drive applications. Firstly, the feasible matches between the slot-pole combinations, stator tooth types, as well as winding topologies are given. Secondly, the expressions of fundamental and harmonic back-EMF are then derived, where the equivalent winding factor considering the air-gap permeance harmonics is introduced to evaluate the back-EMF fundamental amplitude. Next, the contribution of each air-gap magnetic field harmonic on the back-EMF harmonic is investigated, which has proven that the air-gap odd-order ineffective magnetic field harmonics are responsible for unexpected back-EMF harmonics. Based on this, the feasible principle of the number of PM poles, armature poles, and flux modulation poles aiming at the low ineffective back-EMF harmonics is established. Finally, extensive finite element analysis (FEA) is conducted, and two prototypes were manufactured and tested, where the experimental results have a good agreement with the FEA and theoretical results.

Analysis of linear motor with symmetrical EMF vector for household elevator application

&lt;span lang="EN-US"&gt;Linear permanent magnet synchronous motor (LPMSM) has emerged as a viable alternative to other linear motors for higher thrust lifting action. With the advancement of permanent magnets, LPMSM could contribute to energy conversation while also being suitable for applications requiring higher thrust, such as elevator. However, because the existing LPMSM is larger in size, it requires more space to be equipped with a household elevator. To address this issue, a new LPMSM with increased thrust capability has been proposed. The new LPMSM is modelled and analyzed in terms of back EMF and force in this paper. For improved performance, a symmetrical EMF vector is applied to the new LPMSM. In terms of back EMF and force, 4 LPMSM models are studied. According to the results, 6 slot 4 pole has the highest back EMF when compared to the others. As a suitable combination of slot and pole, a symmetrical EMF vector is the suggested LPMSM at the end of this research. &lt;/span&gt;

Design to Reduce Modulated Vibration in Fractional-Slot Concentrated-Windings PM Machines Considering Slot–Pole Combination

The superior torque performance and unsatisfactory vibration are the inherent contradiction issue in fractional-slot concentrated-windings (FSCW) permanent magnet (PM) machines. This article aims to reduce the modulated vibration in FSCW PM machines while preserving their great torque performance. First, the contradictory relationship between the torque performance and the vibration of FSCW PM machines is revealed from the perspective of the slot–pole combination. Then, the radial force modulation of the FSCW PM machine is investigated from the aspects of spatial order and magnitude modulation. Subsequently, a new vibration reduction design methodology is presented, which combines the optimal slot opening coefficient and modified slot–pole combination. Finally, the prototype of a 12-slot/14-pole FSCW PM machine is manufactured, and several simulated and experimental verifications are carried out to validate the theoretical analysis.

Power Factor Analysis in Spoke-Type Permanent Magnet Vernier Motors With Different Slot–Pole Combinations for In-Wheel Direct Drive

This article investigates the power factor characteristic in spoke-type permanent magnet Vernier motors (ST-PMVMs) with different slot–pole combinations for in-wheel direct drive. First, the working principle and power factor expression have been presented, and the influencing factors of the power factor have been targeted. Second, the relationship of slot and pole numbers is illustrated, and the general slot–pole combinations of PMVM with less armature magnetomotive force (MMF) harmonics have been derived and concluded. Then, the armature MMF harmonics, armature reaction magnetic field, and armature reaction reactance components under different slot–pole combinations are illustrated and compared, where a parameter to evaluate the ratio of useless leakage harmonic reactance is introduced. Next, the performances, such as the back EMF, armature reaction magnetic field, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$d$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$q$ </tex-math></inline-formula> -axis inductances, output torque capability, and power factor, are all analyzed. Finally, a prototype was manufactured, and the experimental results match well with the theoretical and FEA results.

Design and Simulation Analysis of Stator Slots for Small Power Permanent Magnet Brushless DC Motors

With the development of power electronics technology, permanent magnet brushless DC motors have developed rapidly and are now widely used in electric vehicles, flywheel energy storage, rail transit, and other applications. The stator slot structure is one of the main factors affecting the performance of the motor. A low-power permanent magnet brushless DC motor was selected as the research object, and the finite element analysis method was used to study the effects of different slot and pole combinations and stator slot types on the cogging torque, reluctance torque, and back electromotive force of the permanent magnet brushless DC motor. The influence of the stator slot structure of the motor on the performance of the motor was analyzed, and the optimal slot-pole combination and stator slot type were determined. The results showed that the cogging torque of the 2-stage 24-slot motor was 14 mN·m, and the reluctance torque was 75 mN·m. The cogging torque and reluctance torque were the smallest, and the back electromotive force waveform was similar to a trapezoidal wave. The motor cogging torque of the pear-shaped round slot was the smallest, with a value of 460 mN·m, and the motor reluctance torque of the pear-shaped trapezoidal slot was the smallest, with a value of 1.2 N·m. The back electromotive force waveforms of the motors with four different stator slot types were similar.