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Ultra-high-speed permanent magnet motors (UHSPPMs) are gradually increasing in the number of scenarios to realize energy saving and emission reduction due to their advantages such as high power density and fast response speed, and their accurate design and analysis are becoming more and more important. UHSPMMs need to consider the effects of multiple physical fields such as electromagnetism, force, and heat on their performance and structure due to their high rotational speed and small size. In this paper, firstly, the loss of each component of the motor is accurately calculated, and the distribution of the flow field and temperature field inside the motor is obtained by computational fluid dynamics (CFD) to determine the limiting working conditions of each component of the motor. Secondly, the mechanical stresses of the rotor are calculated at different limiting working conditions, especially the checking of the stresses of the permanent magnets and the sleeves when they are working at different temperature gradients, in order to improve the reliability of the ultra-high-speed rotor. Furthermore, the dynamics analysis is performed for the whole rotor system to ensure stable operation for a long time at the rated working conditions. Finally, the dynamics of the whole rotor system is analyzed to ensure that the ultra-high-speed permanent magnet rotor can operate stably for a long period of time at the rated operating conditions. Based on the theoretical calculations and analyses, a 25 kW, 95 krpm prototype was designed and fabricated, and relevant experimental studies were carried out. The correctness of the calculation of rotor mechanical properties under extreme working conditions (extreme speed and extreme temperature) is verified through tests, which achieved the target of design accuracy within 5%, and can provide great help to further improve the high-precision design of UHSPMMs. [ABSTRACT FROM AUTHOR]

Background: Trans‐stenotic pressure gradient (TPG) measurement is essential for idiopathic intracranial hypertension (IIH) patients with transverse sinus (TS) stenosis. Four‐D flow MRI may provide a noninvasive imaging method for differentiation of IIH patients with different TPG. Purpose: To investigate the associations between 4D flow parameters and TPG, and to evaluate the diagnostic performance of 4D flow parameters in differentiating patients with high TPG (GroupHP) from low TPG (GroupLP). Study type: Prospective. Population: 31 IIH patients with TS stenosis (age, 38 ± 12 years; 23 females) and 5 healthy volunteers (age, 25 ± 1 years; 2 females). Field Strength/Sequence: 3T, 3D phase contrast MR venography, and gradient recalled echo 4D flow sequences. Assessment: Scan‐rescan reproducibility of 4D flow parameters were performed. The correlation between TPG and flow parameters was analyzed. The netflow and velocity difference between inflow plane, outflow plane, and the stenosis plane were calculated and compared between GroupHP and GroupLP. Statistical Tests: Pearson's correlation or Spearman's rank correlation coefficient, Independent samples t‐test or Wilcoxon rank‐sum test, Intra‐class correlation coefficient (ICC), Bland–Altman analyses, Receiver operating characteristic curves. A P value <0.05 was considered significant. Results: Significant correlations were found between TPG and netflow parameters including Favg,out‐s, Favg,in‐s, Fmax,out‐s, and Fmax,in‐s (r = 0.525–0.565). Significant differences were found in Favg,out‐s, Fmax,out‐s, Favg,in‐s, and Fmax,in‐s between GroupHP and GroupLP. Using the cut‐off value of 2.19 mL/sec, the Favg,out‐s showed good estimate performance in distinguishing GroupHP from GroupLP (AUC = 0.856). The ICC (ranged 0.905–0.948) and Bland–Altman plots indicated good scan‐rescan reproducibility. Data Conclusions: 4D flow MRI derived flow parameters showed good correlations with TPG in IIH patients with TS stenosis. Netflow difference between outflow and stenosis location at TS shows the good performance in differentiating GroupHP and GroupLP cases. Level of Evidence: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Because the magnetic properties of an amorphous alloy (AA) obviously change with the change of temperature, a finite element simulation method for a motor, considering the effect of temperature, is proposed in this paper. In the early design stage of the high-speed permanent magnet synchronous motor (PMSM), the simulation of motor performance is mainly based on the magnetic performance test data at room temperature provided by the material's manufacturer. However, the influence of the temperature rise during the actual operation of the motor will lead to large errors between the simulation results and the measured results. Therefore, it is of great practical significance to measure the magnetic properties of the AA at different temperatures and use them for simulation purposes. In this paper, the magnetization characteristics and iron loss characteristics of the AA and silicon steel (ST100) used for comparison are measured at different temperatures, and the iron loss separation of the two materials at different temperatures is completed, and the hysteresis loss coefficient and eddy current loss coefficient at different temperatures are obtained. On this basis, the performance simulation of a motor model is carried out. The more accurate simulation method proposed in this paper can provide a reference for the design of AA motors in industry. [ABSTRACT FROM AUTHOR]

In the face of the rapid development of the motor industry, some motors with traditional soft magnetic materials can no longer meet the needs of the market. Using new high-saturation magnetic density materials has become a new breakthrough to improve the torque density of motors. Fe-Co alloys (1J22) have high-saturation magnetic induction strength, which can effectively improve the motor's magnetic field strength and increase its torque density. At the same time, the temperature rise of the motor is also an important factor to consider in the motor design process. In particular, the change in core temperature caused by loss makes the coupling of the internal temperature field and the electromagnetic field of the motor more common. Therefore, it is necessary to test the temperature and magnetic properties of 1J22 together. In this paper, a coupling measurement device for magnetic properties of soft magnetic materials is built, and a 1J22 temperature field–electromagnetic field coupling experiment is completed. It is found that the maximum loss of 1J22 decreases by 4.44% with the increase in temperature; the maximum loss is 6.41% less than that of traditional silicon steel. Finally, a finite element simulation model is built to simulate the actual working conditions of the motor, and it is verified that the magnetic properties of the material at high temperature will have a certain impact on the performance of the motor. [ABSTRACT FROM AUTHOR]

Background: Lenticulostriate artery (LSA) obstruction is a potential cause of subcortical infarcts. However, MRI LSA evaluation at 3T is challenging. Purpose: To investigate middle cerebral artery (MCA) plaque characteristics and LSA morphology associated with subcortical infarctions in LSA territories using 7‐T vessel wall MRI (VW‐MRI) and time‐of‐flight MR angiography (TOF‐MRA). Study Type: Prospective. Population: Sixty patients with 80 MCA atherosclerotic plaques (37 culprit and 43 non‐culprit). Field Strength/Sequence: 7‐T with 3D TOF‐MRA and T1‐weighted 3D sampling perfection with application‐optimized contrast using different flip angle evolutions (SPACE) sequences. Assessment: Plaque distribution (superior, inferior, ventral, or dorsal walls), LSA origin involvement, LSA morphology (numbers of stems, branches, and length), and plaque characteristics (normalized wall index, maximal wall thickness, plaque length, remodeling index, intraplaque hemorrhage, and plaque surface morphology (regular or irregular)) were assessed. Statistical Tests: Least absolute shrinkage and selection operator regression, generalized estimating equations regression, receiver operating characteristic curve, independent t‐test, Mann–Whitney U test, Chi‐square test, Fisher's exact test, and intra‐class coefficient. A P value <0.05 was considered statistically significant. Results: Plaque irregular surface, superior wall plaque, longer plaque length, LSA origin involvement, fewer LSA stems, and shorter total and average lengths of LSAs were significantly associated with culprit plaques. Multivariable logistic analysis confirmed that LSA origin involvement (OR, 28.51; 95% CI, 6.34–181.02) and plaque irregular surface (OR, 8.32; 95% CI, 1.41–64.73) were independent predictors in differentiating culprit from non‐culprit plaques. A combination of LSA origin involvement and plaque irregular surface (area under curve = 0.92; [95% CI, 0.86–0.98]) showed good performance in identifying culprit plaques, with sensitivity and specificity of 86.5% and 86.0%, respectively. Data Conclusion: 7‐T VW‐MRI and TOF‐MRA can demonstrate plaque involvement with LSA origins. MCA plaque characteristics derived from 7‐T VW‐MRI showed good diagnostic accuracy in determining the occurrence of subcortical infarctions. Evidence Level: 2 Technical Efficacy: Stage 3 [ABSTRACT FROM AUTHOR]