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Short-circuit protection method for medium-voltage SiC MOSFET based on gate-source voltage detection
Wang, Zhankuo,Tong, Chaonan,Huang, Weichao The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.4
During the short-circuit fault of a two-level bridge converter based on silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs), the SiC MOSFETs may fail within a few microseconds without short-circuit protection. The short-circuit protection of SiC MOSFETs is an essential feature for improving the reliability of converters. This study proposes an improved short-circuit protection method for medium-voltage SiC MOSFETs subjected to shoot-through conditions. In the protection method, the gate-source voltage of the SiC MOSFETs in a half bridge is detected to determine whether a shoot-through short circuit occurs or not. A desaturation protection circuit based on V<sub>DS</sub> measurement for a short circuit is also designed for overcurrent. The protection circuit's validity is verified by the experimental results. Compared with conventional commercial driver integrated circuits, the proposed method can detect and turn off SiC MOSFETs in 0.2 ㎲ under the shoot-through condition. Desaturation protection can be completed in 0.5 ㎲ when overcurrent occurs.
Thermodynamic Performance Analysis of New Paper Machine Air Hood Heat Recovery System
Yan Yan,Wang Weichao,Pan Zhao 한국펄프·종이공학회 2022 펄프.종이기술 Vol.54 No.6
In this paper, a new heat recovery system of hot air hood of paper machine is proposed, the thermodynamic model of the system is established, and the effect of different thermal parameters on the heat recovery efficiency of the system is studied. The results indicate that both the recovered energy and the proportion of exhaust air passing through the latent heat exchanger attenuate as fresh air temperature increase and fresh air moisture content decrease. The system heat recovery increasing with rising of exhaust temperature. Exhaust temperature and exhaust relative humidity have different effects on sensible and latent heat recovery. The maximum value of proportion of exhaust air passing through latent heat exchanger appears when the exhaust relative humidity is 35.8%. Overall, the fresh air temperature and the exhaust relative humidity have great influence on the heat recovery efficiency.
Wei Chao,Long Gongwei,Zhang Yucong,Wang Tao,Wang Shaogang,Liu Jihong,Ma Delin,Liu Xiaming 대한남성과학회 2021 The World Journal of Men's Health Vol.39 No.4
Purpose: Pulsatile gonadotropin-releasing hormone (GnRH) therapy and gonadotropin therapy (GT) were widely used for male patients with congenital hypogonadotropic hypogonadism (CHH), but their efficacy was not well compared before. We conducted this meta-analysis to compare the efficacy of restoring fertility using these two therapies. Materials and Methods: PubMed, Web of Science, and Scopus were systematically searched for comparative studies evaluating the efficiency of GnRH therapy and GT for male patients with CHH. For continuous outcomes, the weighted mean difference (WMD) was used to measure the difference, whereas the risk ratio with 95% confidence interval was calculated for binary variables. Results: Overall, eight articles from seven studies with 420 patients enrolled were included in the analysis. Patients from the two different groups were determined to be comparable in age, proportion with Kallmann syndrome, percentage of cryptorchidism and pretreatment hormones (follicular-stimulating hormone, luteinizing hormone, and testosterone). GnRH therapy was related to a larger testicular volume (standardized mean difference=-1.43; p=0.01) and earlier spermatogenesis (WMD=- 5.30 months; p=0.004) compared to GT. However, the difference in the rate of positive sperm detection (p=0.08), sperm concentration (p=0.37), and pregnancy rate (p=0.11) were not significant. Allergic reactions mostly occurred during GnRH therapy, while GT was related to a higher incidence of gynecomastia and acne. Conclusions: Compared to GT, GnRH was related to earlier spermatogenesis and less estradiol-related adverse reactions, although there were no significant differences in spermatogenesis rate, sperm concentration, and pregnancy rate. High-quality randomized controlled trials are needed for future research.