Search

This study presents an approach for calculating the stress and deformation increase in the modulation of magnetically geared machines using a mathematical method. An analytical method is employed to obtain the magnetic force density acting on the modulation components. Afterward, the proposed mathematical method predicts the mechanical characteristics. The 9 slots/32 poles/19 modulations model was evaluated via a comparison with the finite element method simulation.

This study presents an approach to calculating the temperature increase in the internal components of permanent magnet synchronous machines by applying lumped-parameter thermal networks and analytical methods. Accordingly, the thermal equivalent circuit method is employed to obtain the temperatures of the machine’s internal components. Furthermore, this analytical method predicts the temperature distribution in the slot area. The 24/6 prototype was used to evaluate the proposed model by comparing the calculated and finite element method simulation.

In this study, electromagnetic noise sources of permanent magnet synchronous motors with 8-pole 9-slot and 12-slot fractional slot concentrated windings were analyzed through finite element analysis, and the radiated noise/vibration levels were compared through structural-acoustic analysis. In addition, the stability of the rotational shaft generated vibration was analyzed. Electromagnetic noise sources are classified into cogging torque, torque ripple, and unbalanced magnetic force. The effect of electromagnetic noise sources on vibration/noise was analyzed in the frequency domain through the electromagnetic-mechanical coupling analysis. The noise level was compared to the electromagnetic noise source characteristics for each frequency using the waterfall diagram, and additional vibration due to mechanical resonance was analyzed using critical speed analysis while taking the rotor's bearing stiffness into account.

Although the finite element method (FEM) is highly reliable, it is time-consuming and expensive, for example, substantial computing costs are incurred for coupled analysis while considering the mechanical and electromagnetic properties. Therefore, in this paper, a high-speed permanent magnet generator's electromagnetic and stress characteristics have been mathematically derived, and the optimal point is selected based on NSGA-II. The objective functions are power density and efficiency, with the constraints being the current density, slot fill factor, core saturation, voltage limit, and rotor safety factor. The method presented in this study was verified via FEM analysis and experimental results of the optimal model.

Purpose To report the arthroscopic and clinical findings of patients with extensor carpi ulnaris (ECU) tendinopathy treated with wrist arthroscopy and open surgical repair. Methods We retrospectively reviewed the medical records of seven patients with chronic ECU tendinopathy who were treated with diagnostic wrist arthroscopy and open surgical repair between 2010 and 2017. Seven cases diagnosed with ECU tendinopathy had undergone open procedure for the ECU tendinopathy, as well as wrist arthroscopy in the same session. Any pathology of the triangular fibrocartilage complex (TFCC) diagnosed by wrist arthroscopy were treated simultaneously with open procedure for the ECU tendinopathy. The functional outcome was evaluated by comparing the preoperative and final follow-up values of range of motion (ROM), grip strength, visual analog scale (VAS) for pain, modified Mayo wrist score and quick disabilities of the arm, shoulder, and hand (DASH) score. Results TFCC tears were identified in four patients of which repair was performed concomitantly. The average follow-up period was 39 months (range, 25–49 months). At the final follow-up, all the outcomes including average VAS score (6.4→1), the ROM (173→192°), quick DASH score (42.5→18.2), and modified Mayo wrist score (48.6→79.3) improved significantly. Conclusion When treating patients with ECU tendinopathy, the possibility of TFCC combined injury should always be considered. If surgical treatment is planned, we suggest a wrist arthroscopy for more accurate diagnosis an intra-articular pathology, particularly for patients whose MRI findings suggest a degenerative tear or degeneration at the periphery of the TFCC. Additionally, if ECU and DRUJ stability is obtained by repair or reconstruction of the concurrent pathologies in the ECU subsheath, TFCC and other intra-articular structures, the results will be favorable.

Purpose Early detection and classification of bone tumors in the proximal femur is crucial for their successful treatment. This study aimed to develop an artificial intelligence (AI) model to classify bone tumors in the proximal femur on plain radiographs. Methods Standard anteroposterior hip radiographs were obtained from a single tertiary referral center. A total of 538 femoral images were set for the AI model training, including 94 with malignant, 120 with benign, and 324 without tumors. The image data were pre-processed to be optimized for training of the deep learning model. The state-of-the-art convolutional neural network (CNN) algorithms were applied to pre-processed images to perform three-label classification (benign, malignant, or no tumor) on each femur. The performance of the CNN model was verified using fivefold cross-validation and was compared against that of four human doctors. Results The area under the receiver operating characteristic (AUROC) of the best performing CNN model for the three-label classification was 0.953 (95% confidence interval, 0.926–0.980). The diagnostic accuracy of the model (0.853) was significantly higher than that of the four doctors (0.794) (P = 0.001) and also that of each doctor individually (0.811, 0.796, 0.757, and 0.814, respectively) (PConclusions The AI-based model demonstrated high performance in classifying the presence of bone tumors in the proximal femur on plain radiographs. Our findings suggest that AI-based technology can potentially reduce the misdiagnosis of doctors who are not specialists in musculoskeletal oncology.

A surface-mounted permanent magnet synchronous motor (SPMSM) is an electric motor with a simple magnetic circuit design, fast responsiveness, linear torque–current characteristics, speed–voltage characteristics, and constant operating speed. SPMSMs use only magnetic torque; however, interior PMSMs (IPMSMs) have high power densities because they can use reluctance torque. In addition, when flux-weakening control is used, the operating range is wide compared with the SPMSM. This study presents a comparative analysis of the characteristics of SPMSM and bar-type IPMSM. Characteristic analyses are performed by setting the same stator shape, rated speed, number of turns, winding specifications, voltage limit, and magnet usage in a pole/slot combination of six poles and 27 slots. Next, we compare the no-load back electromotive force, cogging torque, and loss characteristics, and perform a characteristic analysis of each model while satisfying the design specifications. No-load and load tests are performed using a back-to-back system. The results of the analysis and experimental results are in good agreement, and the reliability of the analysis results is guaranteed. The SPMSM is approximately 8.5% superior to the IPMSM in terms of core loss, and the eddy current loss is greater than that of the IPMSM.

In contrast to internal combustion engine vehicles, electric vehicles (EVs) obtain the power required for the compressor of air conditioning system from an electric source. Therefore, an optimal design for electric motor, the main component of an electric compressor, is essential for improving EV mileage. A multi-objective optimal design is required because the characteristics of the motor are in a trade-off relationship with each other. When the finite element method (FEM) is used, multi-objective optimal designs for the motor take a significant amount of time because of the diversity analyses required for the optimal-model search. To solve this problem, in this study, a multi-objective optimal design method of an SPMSM for an EVs air conditioner system compressor was proposed and applied using the NSGA-II and an analytical method. The validity of the proposed method was confirmed by comparing the characteristics of the optimal design model with those of the initially designed model.

This paper is about the magnetic field analysis of an interior permanent magnet motor (IPM motor) by using the equivalent magnetic circuit method (EMC method), which requires a small amount of computation time compared with the finite element method (FEM). IPM motors have a specific shape of rotor in which the permanent magnets are embedded. Therefore, in the bridge region, the magnetic saturation is generated due to the shape of the permanent magnet, which affects the magnetic flux density distribution in the air gap and the characteristics of the IPM motor. Thus, to design an IPM motor, the magnetic saturation effects should be considered along with the rotor shape. In addition, because the rotor of the IPM rotates at a high speed directly in connection with the load, the stress generated from the rotor must be stably distributed. Consequently, according to the rotor shape characteristics of the IPM, the stress is concentrated in the thin bridge region during high-speed rotation. When the stress generated in the bridge region exceeds the yield stress of the rotor iron core material, the bridge part is destroyed. Therefore, it is important to analyze the stress that occurs in the rotor during high-speed rotation in the rotor design stage of the IPM. In this study, we analyzed the magnetic field characteristics of an IPM motor using its equivalent magnetic circuit while considering the magnetic saturation in the bridge region. The stability of the rotor was determined by presenting a safety factor based on the maximum stress generated at the rotor for each speed. We derived the stator natural frequency to evaluate the resonance possibility between the electrical frequency and the stator natural frequency. Finally, the validity of the constructed equivalent magnetic circuit was verified by comparing the results with those obtained via the FEM analysis and experiments.