Mechanical Fault Detection in Induction Motor Drives through Stator Current Monitoring - Theory and Application Examples

Available from: http://sciyo.com/articles/show/title/mechanical-fault-detection-in-induction-motor-drives-through-stator-current-monitoring-theory-and-apIn a wide variety of industrial applications, an increasing demand exists to improve the reliability and availability of induction motor drives. Common failures occurring in such drives can be classified into electrical and mechanical faults (rotor eccentricity, bearing faults, shaft misalignment, load unbalance, gearbox fault or general failure in the load part of the drive). Mechanical faults are most commonly detected through vibration or noise monitoring, but stator current monitoring is an interesting alternative. Indeed, current sensors are cost-effective, easy to implement, and most drives already contain such sensors for protection and control purposes. However, the effects of mechanical faults on the stator currents are more indirect compared to vibration or noise analysis. This work focuses on various aspects of mechanical fault detection through stator current monitoring, starting from a general theoretical analysis to signal processing methods for fault detection and several application examples

Sexual behavior and factors associated with young age at first intercourse and HPV vaccine uptake among young women in Germany: implications for HPV vaccination policies

Background: In Germany, immunization against human papillomaviruses (HPV) is free of charge for all females aged 12 to 17 years. Since HPV infection rates rise soon after first intercourse, immunization against HPV should be completed before sexual debut. Knowledge of country-specific data on age at first intercourse and related risk factors is important to optimize prevention of HPV and other sexually transmitted infections. Therefore, the primary aim of this study was to describe sexual behavior in young women in Germany. Secondary aims were to identify factors that are (i) associated with younger age at first intercourse and (ii) with HPV vaccine uptake. Methods: Between 2010 and 2012, we conducted a cross-sectional study among randomly selected women aged 20 to 25 years in Germany. We used a structured, self-administered questionnaire to collect sociodemographic data, information on sexual habits such as age at first intercourse, and information on HPV vaccine uptake. We used univariate and multivariate logistic regression analyses to identify factors associated with younger age at first intercourse and with HPV vaccine uptake. Results: A total of 823 women (response rate: 14.2%) participated, 785 (95.4%) of which reported having had intercourse already. 70% of these women experienced first intercourse before the age of 18 years. However, less than 5% were younger than 14 years at sexual debut. Younger age at first intercourse was independently associated with a higher number of sexual partners, smoking, and past pregnancies. HPV vaccine uptake was associated with higher education, whereas smoking and a migrant background reduced the chance of being vaccinated. Conclusion: In Germany, only a small proportion of women experienced first intercourse before the age of 14 years. Younger age at first intercourse was associated with behavior that might increase the risk of HPV infections or other sexually transmitted infections. Therefore, to optimize the HPV vaccination strategy, HPV vaccination series should be completed before the age of 14 years in Germany

Modal Decomposition for Bearing Fault Detection

International audienc

Method of analysing non-stationary electrical signals

International audienceConsidering the non-stationary operating conditions of wind turbines, electrical signals measured at the stator of their generators will also present variations around their fundamental frequency. This paper presents a method able to efficiently analyse electric quantities measured at the generator stator. The obtained outputs consist in electrical fea-tures that fully describe the electrical information contained in the mea-sured three-phase quantities. These features can be directly used or fur-ther analysed to obtain efficient fault indicators. The proposed method relies on using the instantaneous symmetrical components to describe the quantities and complex-valued filtering to select the content around the fundamental frequency. The obtained sample per sample algorithm can be implemented on-line, and is able to process stationary or non-stationary quantities in order to extract the useful information around the fundamental frequency. The performance of the proposed method, as well as its capability to detect mechanical faults, is illustrated using experimental data