With the rapid growth of AI data centers, high-efficiency electrical machines have become increasingly important for HVAC applications. Outer-rotor surface permanent magnet synchronous motors (SPMSMs) with ferrite magnet are widely adopted for electrically commutated (EC) fans in AI data centers due to their low cost and high efficiency. Since the electromagnetic performance of SPMSMs is significantly influenced by the permanent magnet shape, extensive studies have been conducted to improve efficiency and reduce torque ripple. In this paper, a comparative study of outer-rotor PMSMs with four permanent magnet shapes—chamfer, linear chamfer, taper, and cycloid—is conducted for EC fan applications. For a fair comparison, all models are optimized under identical constraints using a multi-objective genetic algorithm (MOGA) based on finite element analysis (FEA). Electromagnetic characteristics, including back electromotive force (BEMF), torque, torque ripple, and efficiency, are evaluated The results show that the chamfer-type magnet achieves the highest efficiency despite slightly higher harmonic components. To validate the FEA results, a prototype is manufactured and experimentally evaluated under both no-load and load conditions. The FEA results are validated through the comparison with the experimental results, demonstrating a BEMF error of 1.4%and an efficiency deviation of less than 1 %. In addition, the efficiency of the prototype motor satisfy the IE5 efficiency class according to the IEC 60034-30-2.

This article presents a time-efficient redesign process of a wound-field synchronous motor (WFSM) for use in an electric mini cargo truck (EMCT) intended for short-distance operations. Considering the driving cycle, the proposed design process utilises extended scaling laws and MS-FEA. This approach is demonstrated using a 22kW WFSM with fixed core dimensions as a case study and design process is proposed as follows: 1) The required torque-speed characteristics of the redesigned motor are determined from the New European Driving Cycle (NEDC); 2) Motor performance parameters are explored through parametric analysis; 3) The terminal voltage limit can be satisfied by adjusting stator winding parameters, such as the number of turns and parallel paths while considering the highest efficiency operating points. The rotor winding parameters can be determined from the voltage level constraints in the rotor winding, which are affected by the design of the contactless power system in the EMCT model.

In this paper, a 150 W small wind power generator which has a permanent magnet synchronous generator type is proposed with a new straight shape stator and rotor to reduce the cogging torque. The advantages of the proposed structure are introduced through a comparison between the basic and the proposed models. By comparing the pole slot combination of the proposed generator, the combination with optimal cogging torque characteristics was selected. The electromagnetic characteristics of the proposed shape are analyzed for design variables using a finite element analysis of ANSYS 2021 R1 Maxwell. The final model of the proposed structure is designed by considering the cogging torque and electromagnetic characteristics of the generator. The electromagnetic and structural simulations of the final model are performed to satisfy the required performance of the generator and mechanical safety. To verify the FEA results of the final model, a prototype is manufactured, experimented, and compared with the FEA results.

This paper presents an efficient method for calculating AC copper loss in interior permanent magnet synchronous motor (IPMSM) with rectangular conductors, considering pulse width modulation (PWM) current harmonics. The inverter-fed current for driving IPMSM can be decomposed into fundamental and harmonic currents. The proposed method first utilizes magneto-static finite element analysis (MS FEA) to compute the magnetic vector potential (MVP) generated by the fundamental current. Next, the frozen permeability method linearizes the FEA model by keeping the permeability of iron core. A single harmonic current is input into linear-MS FEA to compute MVP without permanent magnet excitation. The MVP of other harmonic currents are derived using linear fitting. The linear fitting of MVP is validated with FEA. Finally, the AC copper loss is then calculated by summing the contributions from the MVP of each current component.

This research proposes a bi-directional electromagnetic-thermal coupled analysis model based on node-to-node data transfer for a totally enclosed air over (TEAO) permanent magnet synchronous motor (PMSM) for a high-speed train (HST) distributed traction (DT). The study begins by highlighting the advantages of the DT-HST system and identifying the heat sources within the traction motor based on design requirements. A bi-directional coupled model is then introduced to evaluate the physical performance of the proposed traction motor under various operating conditions, including rated and continuous power ratings. This model combines electromagnetic and thermal models and utilizes node-to-node data transfer to update material characteristics, such as electromagnetic losses and temperature, ensuring accurate predictions of machine performance. The simulation results were used to develop a prototype, which was subsequently tested and compared against the simulation results. The comparison between the bi-directional simulation model and test results demonstrates good agreement in terms of temperature rise. Specifically, for the winding active and end parts, the temperature deviations between the bi-directional simulation and test results were found to be only 0.01%, 1.4%, and 1.7%, 1.8% for continuous and full-rated ratings, respectively. As for the ferromagnetic core, the deviations were 11% and 5.8%. Similarly, the PM temperature recorded by the test setup exhibited deviations of 3.3% and 8.3% compared to the simulation results under continuous and full-rated operations.

This study investigates how operating conditions such as ambient temperature and sealing pressure affect sealing performance for a typical U-cup seal. The developed analysis method combines inverse fluid lubrication (IHL) theory and the Greenwood–Williamson contact model (G–W model), and the effect of increasing surface temperature due to frictional heat generated between two surfaces is considered. Commercial FE software (ABAQUS) was used to simulate the interference fit analysis of rubber seals and the pressurized process. Through this model, the film distribution, working fluid leakage, and friction force in the sealing area were discussed according to the operating parameters, such as sealed pressure, rod velocity, and ambient temperature. The simulation results demonstrate the effect of fluid viscosity on oil film formation (which varies with ambient temperature), the effect of increasing the surface temperature, and the effect of surface roughness at a very small film thickness.

Thermal deformation of journal bearings operating under high-temperature conditions can have a significant effect on changes in bearing performance. However, no attempt has been made to quantify this amount of thermal deformation and link it to the performance change of the bearing. The aim of this study is to investigate the quantitative performance change due to thermal deformation of the tilting pad journal bearing (TPJB) pad in terms of the change in preload amount. The variable viscosity Reynolds equation and the energy equation were coupled using the relationship between viscosity and temperature, and the solution was obtained using the finite element method. Heat transfer between the spinning journal, oil film and pads is considered, and a three-dimensional (3D) finite element (FE) model was used to calculate the thermal deformation of the bearing structure. The steady state of the rotor-bearing system was predicted using a bearing performance prediction algorithm with three closed loops. State variables for this steady-state prediction include the amount of thermal deformation of the structure. In order to investigate the amount of thermal deformation of the bearing pad in terms of bearing performance, the concepts of thermal offset preload and thermal performance preload were suggested and the change in thermal preload under various conditions was investigated.

The Korean government is facing growing concern over the increasing levels of fine dust. A significant contribution to this problem comes from coastal vessels. To mitigate this, an electric ship propulsion system has been proposed as a solution to reduce air pollution. The application of a fully electric propulsion system in a ship is challenging due to size, capacity limitations, and the cost investment of the battery system. To address the challenges of battery limitation and initial investment costs, the development and supply of removable battery supply systems (RBSSs) for fully electrified battery powered (F-EBP) car ferries are studied. A permanent magnet synchronous motor (PMSM) for the F-EBP car ferry using a roll-on/roll-off-type RBSS is developed in this work. Firstly, the concept of the F-EBP car ferry is discussed, and the specifications of the electric car ferry propulsion system are provided. Secondly, motor design and electromagnetic analysis are performed using finite-element analysis (FEA), where the heat sources including copper loss, core loss, and PM loss are calculated. Mechanical loss is also considered. Finally, a thermal network of the motor is built considering the lumped-parameter model. The results of the thermal analysis indicate that the motor operates within the safe region and can perform well in rated working conditions.

Railway electrification has posed a challenge for power quality in railway networks due to their unique characteristics. This research paper explores the impact of an inductor filter on high-order harmonic currents generated by the pulse-width modulation (PWM) converter in the traction drive of high-speed railway (HSR) systems. The paper begins by providing an overview of the traction power transfer system (TPTS) in a HSR and models a permanent magnet synchronous motor (PMSM) for traction applications. Then, a laboratory-based system (LBS) HSR is built to replicate the energy flow characteristics observed in a real-world HSR system. The LBS-HSR is modeled in Matlab/Simulink and is utilized to analyze the harmonic spectrum of current on the grid and motor terminal under various operating conditions. Furthermore, the paper investigates the impact of the inductor filter on other system components such as the input current of the converter and the voltage on the DC capacitor. Finally, a laboratory-based HSR system is developed on experiment and validated against the results obtained from the simulation model.

This paper presents a critical review of traction motors used for distributed traction (DT) applications in high-speed railways (HSR). The motor topologies that can be used for DT-HSR are presented. The advantages and disadvantages of each motor in terms of structural and electromagnetic performance are discussed from the perspective of motor design. A survey of the advancement of the HSR industry in South Korea is presented, and the required torque–speed profile for the HSR traction motors for the South Korean railway is studied. Along with the electromagnetic design, detailed structural modeling constraints such as the framing design, slot insulation, end-winding potting, and slot wedge modeling are explained.

A totally enclosed air over (TEAO) permanent magnet synchronous motor (PMSM) for the distributed traction (DT) application of high-speed train (HST) is developed in this work. A study on the usefulness of the DT-HST is performed first. Considering the design requirement, electromagnetic and thermal models of the proposed traction motor are developed to check the operation under different operating conditions such as the machine rated power ratings. Based on the simulation model a prototype is developed and validated against the simulation result.

Based on the shock absorber size and power and power density limitations in motorcycle application, a linear permanent magnet machine for a regenerative suspension system that recovers the kinetic energy originating from shock absorber vibration is investigated. To achieve the target power of 120 W, several design parameters were investigated. The eight-slot eight-pole combination was used due to its high power density. A hybrid permanent magnet structure was implemented which was a combination of a classical Halbach array and iron spacers. In addition, the dimensions of the permanent magnet, and stator inner radius were parametrically studied to enhance the air-gap flux density and coil volume, which are the main factors affecting performance. The detailed design generated 124 W of average power under the rated condition, assuming a vibration speed of 0.157 m/s. Despite the satisfaction of the output power and power density, the large magnetic force caused by the interaction between the iron core and permanent magnet is the main drawback of this design, which has a negative impact on driving safety and comfort. To commercialize the suggested device, additional studies will focus on size, electromagnetic reduction, as well as road test performance.

This study analyzed adhesive wear in periodic sliding motion using a quasi-static deterministic wear model that considered changes in the point of contact of asperities as well as changes in the surface and statistical parameters. The contact pressure was calculated using the semi-analytical method (SAM) based on the periodic properties of the rough surface, and the wear was analyzed by obtaining the wear depth for each node using the Archard wear model. We took into account that the sliding distances of the upper moving surface and the lower stationary surface are different according to the actual size of the two objects. We compared the results of the quasi-static wear analysis with the truncation model and the deterministic fixed model, which did not consider the change in the asperity contact point. In the truncation model, an error in the estimation of the radius occurred in the process of fitting the tip of asperities with a sphere. As the asperities became flatter by wear, this error accumulated, which revealed a difference in the deterministic wear analysis results. As a result of the wear analysis on the periodic surface, the RMS roughness of the positively skewed surface decreased the fastest, the skewness increased in the negative direction, and the kurtosis initially decreased and then increased. In addition, wear scars occurred due to the difference in wear depth between the lower stationary surface and the upper moving surface.

The motor of the electric bike is crucial to the overall performance of the bike. A lightweight but powerful and reliable motor is required for electric vehicles. A Brushless permanent magnet motor is selected to meet those requirements. Axial-flux machine topology and Halbach-array are utilized in the motor design to further increase the power density. The tooth-tips in the stator core are removed to simplify the manufacturing process and reduce core weight. The rotor position is detected by the utilization of Hall sensors. Electromagnetic and thermal analyses are performed with three-dimensional finite element analysis to shows the advantage of such topology in an electric bike. A prototype is manufactured and tested at rated conditions to validate analysis results.

This paper investigates an energy-harvesting system that uses of vibration energy at a shock absorber for electric vehicles. This system mainly comprises a linear electromagnetic generator and synchronous buck converter. To obtain the electrical energy through a linear electromagnetic generator, the perturb and observe maximum power point tracking (P&O MPPT) scheme is applied at the converter. The power converter circuit is designed with a diode rectifier and synchronous buck converter. The generated electric power is able to transmit to the battery and the damping force of the shock absorber is adjusted by the controlled current of generator. The linear electromagnetic generator was designed as a single phase eight-slot eight-pole tubular permanent magnet machine. The performance of the proposed energy-harvesting system was verified through simulations and experiments.

Since line-start synchronous permanent magnet motors (LSPMs) entered the market, they have attracted research interest toward counterpart induction motors of low power-ratings. This paper reports an investigation of line-start synchronous reluctance motors (LS-SynRMs). LS-SynRMs has not been investigated as much as LSPMs have. A motor needs to maximize rotor saliency to achieve high efficiency and a high power-factor. This results in complicated rotor geometry because the rotor cage and multiple flux barriers share the same rotor space. This paper provides an approximate method based on steady state torque analysis by which to estimate the critical inertia of a LS-SynRM. A finite element analysis (FEA)-aided analytical approach to the approximation of steady state torque is proposed to replace the more typical approach based on equivalent circuit parameters. The critical inertia resulting from the proposed method is compared to the results obtained using the FEA.

Based on the dimensions and thresholds of power and power density of a commercial shock absorber in the Korando car (an SUV branch), a single-phase 8-slot 8-pole tubular permanent magnet (PM) machine was designed and fabricated. The main focus of this paper is on the increase of output power in a given space and reduction of the volume. This is successfully solved using a novel structure for PM and considering a number of slot-pole combinations. Furthermore, a multiobjective optimization is performed to find the tradeoff between various objectives. The experimental results reveal that the proposed machine can possibly regenerate a maximum of 339.95 W and an average of 96.67 W in terms of its output power. Considering the active volume, which includes PM, iron core, pure copper, and an electromagnetic air gap, the estimated maximum and average power density are 0.311 and 0.087 W/cm(3), respectively. Despite these satisfactory results, one of the major drawbacks to exploiting this machine is its high electromagnetic force, which causes negative effects on safety and driving comfort. With the aim to commercialize the proposed device, further work will be concentrated on the reduction of electromagnetic force and on performance of the road tests.

This paper investigates the mechanical cutting effect on the performance of induction motors. Numerical modeling of cutting effect is described in this paper. The approach inverts the degradation of the permeability model for inclusion of it into magnetic vector potential formula by Newton method. The effect of cutting on iron losses is implemented in finite element simulation. The simulation results are compared with experimental results of prototype IE4 efficiency induction motors rated at 2.2 kW. One of them was manufactured with annealed electrical steel lamination to highlight the cutting effect on the performance of the motor. The notable effect of cutting was measured in increased stator current; however, negligible differences were found in measured iron losses. The presented model in this paper follows the measurements.

This article presents an optimal design of an exterior permanent magnet (PM) tubular machine for energy harvesting from vehicles suspension systems. By using a hybrid structure, in which, the mechanical damper remains and electrical components are attached to the damper's frame, the damping force and damping coefficient are still ensured while wasted kinetic energy is recovered. To maintain driving comfort and safety, the detent force and electromagnetic force must be minimized. The constraints for dimensions of the exterior PM tubular machine were obtained from an actual shock absorber from a school bus, a large-size vehicle. Different topologies were investigated to maximize the output power and power density, while the electromagnetic force was minimized and negative effects of the initial positions to the machine's performance were mitigated. Finite element analysis showed that maximum and average power from an optimal design were about 210.2 and 103.7 W, respectively. To verify the validity of the design, a prototype was fabricated and tested.

As international regulations of motor efficiency are strengthened, the line-start synchronous reluctance motor (LS-SynRM) is being studied to improve the efficiency of the electrical motor in industrial applications. However, in industrial applications, the power factor is also an important performance index, but the LS-SynRM has poor power factor due to the saliency characteristic. In this paper, the rotor design of LS-SynRM is performed to improve the efficiency and power factor. First, the barrier design is performed to improve the efficiency and power factor using the response surface method (RSM). Second, the rotor slot design is performed according to the length of bar for synchronization. Lastly, the rib design is performed to satisfy the power factor and the mechanical reliability. The final model through the design process is analyzed using finite element analysis (FEA), and the objective performance is satisfied. To verify the FEA result, the final model is manufactured, and experiment is performed.