SKF大型混合陶瓷深沟球轴承——风力发电机的可靠解决方案

早期的风力发电机轴承失效频繁发生,原因多种多样,在研究应用条件和调查轴承失效的基础上,基本确认了造成轴承失效的根本原因:双馈感应发电机变频驱动所导致的轴承过电流和相应的电腐蚀及润滑、磨损等。对风力发电机轴承早期失效的根本原因进行论述,同时介绍了SKF最新大型混合陶瓷深沟球轴承在减小轴承失效、增加运行可靠性方面的优势及其在风力发电机应用中的解决方案。     

Nutrition and osteoporosis: a nutritional analysis of women in postmenopause

In a cross-sectional study the effects of several nutritional factors on the manifestations of osteoporosis were investigated in 23 postmenopausal women aged 50 to 70 years. Twelve women (group 1) with osteoporosis and eleven healthy control subjects (group 2) were instructed to keep a seven-day nutritional record. Body mass index (BMI) was recorded, and radiological and bone mineral density investigations were undertaken. The daily total energy, protein, fat, carbohydrate, fiber, oxalic acid, calcium, magnesium, phosphorus, sodium, fluoride, zinc, copper, manganese, vitamin C, D, and K intake were analysed within the framework of a nutritional science program. No intergroup differences were observed with regard to total energy intake, nutritional components and BMI; however, age and years since the menopause differed significantly (p < 0.05). The results suggest that the manifestation of osteoporosis in women is influenced to a greater extent by age and years since the menopause than by the distribution of nutritional factors in a normal mixed diet. However, further studies are essential to evaluate the role of dietary composition on the manifestations of osteoporosis.     

风力发电机中轴承的过电流问题

介绍了异步电动机中寄生电流的起因和影响,同时指出了双馈发电机与异步电动机在这方面的区别。讨论了轴承的一般电气性能,并展示了轴承损伤内部机理的最新研究成果。     

SKF大型混合陶瓷深沟球轴承——风力发电机的可靠解决方案

早期的风力发电机轴承失效频繁发生,原因多种多样,在研究应用条件和调查轴承失效的基础上,基本确认了造成轴承失效的根本原因：双馈感应发电机变频驱动所导致的轴承过电流和相应的电腐蚀及润滑、磨损等。对风力发电机轴承早期失效的根本原因进行论述,同时介绍了SKF最新大型混合陶瓷深沟球轴承在减小轴承失效、增加运行可靠性方面的优势及其在风力发电机应用中的解决方案。     

Linking Structure and Parametric Geometry

The Karamba plug-in developed by Clemens Preisinger in collaboration with Bollinger + Grohmann Engineers has been developed to predict the behaviour of structures under external loads. Intended to be used by architects rather than being solely confined to an engineering setting, it enables a seamless flow of data between structural and geometric models. Preisinger here describes the program's evolution and application.     

Stahlbetonschalen ohne Schalung – ein neuer Weg im Schalenbau

Reinforced Concrete Shells without Formwork – a new Approach to the Construction of RC‐Shells Diversity of designs, slenderness and elegance are the qualities of RC‐shells that leave one amazed at the sight of such structures. New architectural schools are currently about to induce a renaissance in shell structures, at least for public prestigious buildings. The main obstacle, that inhibits a more widely acceptance of those aesthetically pleasing shell‐structures is their cost of construction. One of the biggest cost‐factors in case of geometrically more complex designs is the construction of the formwork. Yet the placement of reinforcement and concrete turns out often to be equally complicated and thus costly. A new shell construction method developed at the Vienna University of Technology relies on post‐tensioning a RC‐membrane into a spatially bent shell, thus cutting the cost of construction considerably.     

Investigation of the physical mechanisms in rolling bearings during the passage of electric current

With the increasing use of frequency converters as control units for electric motors, bearing failures caused by the passage of electric current through the bearings are more common. This paper discusses the most relevant parasitic current loops in frequency converter‐driven motors that can lead to damage of bearing raceways or deterioration of lubricants. Electrical stray capacitances, which are inevitably present in any electric motor, in combination with the high‐frequency components of the drive voltages, have been identified as the source of electric discharge machining (EDM) currents. Based on an EDM equivalent electric circuit, the passage of electric current through the rolling contact of a bearing is simulated. A set‐up is introduced to initiate EDM processes in bearings under well‐controlled electrical and mechanical conditions. The effect of EDM currents on bearing elements in the presence of different lubricants is studied. Initial results are presented.