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1. A Review of Segmented Stator and Rotor Designs in AC Electric Machines: Opportunities and Challenges

   https://doi.org/10.3390/eng6010007  

   Khoshoo, Bhuvan; Aggarwal, Anmol; Foster, Shanelle (January 2025, Eng)

   The use of segmented stator and rotor designs in AC electric machine construction offers several significant advantages, including a high-copper fill factor, increased torque density, improved field-weakening performance, simplified manufacturing processes, and enhanced mechanical strength. Additionally, segmented designs allow for the incorporation of oriented steel—either partially or fully—which exhibits excellent magnetic properties in the rolling direction, resulting in more efficient machine performance. However, lamination segmentation also introduces challenges. Parasitic air gaps between segments and an increased number of cut edges in the assembled stack can alter the magnetic properties of the machine, potentially leading to degraded performance. Furthermore, the use of oriented steel remains complex, as its highly nonlinear magnetic properties vary depending on the direction of the magnetic flux. This paper reviews the widely adopted stator and rotor segmentation techniques available in the literature, discussing their potential benefits and limitations. It also covers key aspects such as popular manufacturing approaches, the impact of segmentation on machine performance, advanced finite-element analysis (FEA) techniques for numerical modeling, and experimental methods for evaluating the performance of segmented stator and rotor constructions in AC machines. By addressing these areas, this work provides a comprehensive resource for machine designers seeking to develop AC machines with segmented stators and rotors. 

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2. Novel Design of Six-Phase Spoke-Type Ferrite Permanent Magnet Motor for Electric Truck Application

   https://doi.org/10.3390/en15061997  

   Won, Hoyun; Hong, Yang-Ki; Choi, Minyeong; Platt, Jonathan; Bryant, Briana; Choi, Seungdeog; Li, Shuhui; Yoon, Hwan-Sik; Haskew, Timothy A.; Lee, Jongkook; et al (March 2022, Energies)

   This paper proposes a 300 kW 24-slot/10-pole 6-phase stator-shifted fractional-slot concentrated winding spoke-type ferrite permanent magnet machine for electric truck applications. The proposed motor consists of a stator with dual three-phase windings positioned 75 degrees apart to reduce higher-order MMF harmonic order, and a rotor with an inexpensive and high-resistance ferrite permanent magnet in the spoke configuration. The simulated result of the stator-shifted machine is compared with a fabricated stator-shifted machine, and the results show good agreement with each other. To further reduce the torque ripple from 2.5 to 0.9% while maintaining a high maximum torque of 2980 Nm, circular voids with a diameter of 11 mm are embedded in the rotor. The proposed motor is evaluated for irreversible demagnetization, mechanical and thermal stability, and fault tolerant ability. To assess the proposed motor performance, the electric truck simulation model is constructed using MATLAB/Simulink and used to compare with the reported 12-slot/10-pole rare-earth permanent magnet-based machine. Compared to a previously reported six-phase rare-earth permanent magnet based flat-type machine, the proposed motor can save 4.3 kWh of energy with a USD 2512 lower cost while retaining a similar motor performance. 

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3. A Review of Ring Motors with Integrated Loads

   Asgodom, Adonay; Noguchi, Takahiro; Nishanth, FNU; Severson, Eric L (October 2024, IEEE Energy Conversion Congress and Exposition)

   Ring motors are electric machines that are typically characterized by having a hollow rotor / stator, a small difference between the inner and outer radii, and a large outer diameter relative to the axial length. The hollow portion of the ring motor allows integrating loads, such as an aerial or marine propeller, enabling power-dense systems. This paper reviews integrated ring motor designs from literature across different applications. Based on this review, first, design trends and performance parameters are identified and compared with conventional radial flux machines. Next, the bearing challenges posed by the unique form-factors of these machines are identified and approaches to realize bearings are presented. Finally, a research outlook is presented that identifies the benefits of applying multi-physics optimization, additive manufacturing, and bearingless machine technology to realize improved integrated ring motor designs. 

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4. Designing a Continuously Variable Magnetic Gear

   https://doi.org/10.1049/cp.2016.0223  

   Pritchard, J.; Padmanathan, P.; Bird, J.Z. (January 2016, 8th IET International Conference on Power Electronics, Machines and Drives (PEMD 2016))

   This paper investigates the performance capabilities of a continuously variable magnetic gearbox that utilizes a flux focusing rotor structure. A fractional slot stator winding is designed to couple to the outer rotor of an existing magnetic gearbox in order to enable the magnetic gearbox to operate with a variable gear ratio. 

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5. The swimming defect caused by the absence of the transcriptional regulator LdtR in Sinorhizobium meliloti is restored by mutations in the motility genes motA and motS

   https://doi.org/10.1111/mmi.15247  

   Sobe, Richard C.; Scharf, Birgit E. (March 2024, Molecular Microbiology)

   Abstract The flagellar motor is a powerful macromolecular machine used to propel bacteria through various environments. We determined that flagellar motility of the alpha‐proteobacteriumSinorhizobium melilotiis nearly abolished in the absence of the transcriptional regulator LdtR, known to influence peptidoglycan remodeling and stress response. LdtR does not regulate motility gene transcription. Remarkably, the motility defects of the ΔldtRmutant can be restored by secondary mutations in the motility genemotAor a previously uncharacterized gene in the flagellar regulon, which we namedmotS. MotS is not essential forS. melilotimotility and may serve an accessory role in flagellar motor function. Structural modeling predicts that MotS comprised an N‐terminal transmembrane segment, a long‐disordered region, and a conserved β‐sandwich domain. The C terminus of MotS is localized in the periplasm. Genetics based substitution of MotA with MotA_G12Salso restored the ΔldtRmotility defect. The MotA_G12Svariant protein features a local polarity shift at the periphery of the MotAB stator units. We propose that MotS may be required for optimal alignment of stators in wild‐type flagellar motors but becomes detrimental in cells with altered peptidoglycan. Similarly, the polarity shift in stator units composed of MotB/MotA_G12Smight stabilize its interaction with altered peptidoglycan. 

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