Impact testing of hydro generators end-winding in different temperature state

The fault detection of rotating electrical machines has become very attractive field of research from vibrational aspect, because these machines are susceptible to failure due to thermal, electrical, mechanical or environmental stresses. Therefore, the vibrational analysis of generators as rotating machines will be beneficial for the generator design in the initial stage and also for online monitoring and faults diagnostics during generator operation. This paper presents a novel methodology for hammer impact testing („bump-test“) of stators end-winding vibrations with an accent on the influence of the physical parameters such as temperature. Introductory, a brief survey of recent research in the area is presented. Furthermore, a detailed description of the used instrumentation and conducted testing methodology according to established standards is systematically exposed. The measurement methodology is implemented on two generators, a cold one in its‘ repairing phase and second identical, generator in a warm condition in order to detect the damaged elements and to investigate the influence of the temperature on the dynamic characteristics (natural frequencies and rigidity) of the structures. A year later, series of same measurements on one of the generators during a process of its’ cooling were conducted. This work provides graphical, as well as numerical results for the dynamical behaviour of the structures under different thermal conditions. Ultimately, a conclusion for the dependence between the temperature and the dynamics parameters of the generator is drawn

Impact testing of end-winding in two hydro generators in different temperature state

A reliable operation of generators is highly dependent on the electrical and mechanical integrity of stator end-winding vibration and has been a major concern in the last two decades. This paper focuses on the experience in hammer impact testing of end-winding vibrations of parallel phase leads and series loop caps in two hydro generators in a different temperature state. The measurements were conducted using hammer testing on the two generators separately and a discussion and comparison of the results was presented in order to perceive the dependence of the temperature and dynamic characteristics of the structures. Introductory, a brief survey of recent research progress in monitoring the end-winding vibrations in generators is presented. Subsequently, a detailed description of the performed measurement, starting from the identification of the object and conducted testing methodology according to established standards is systematically exposed. Ultimately, a paramount accent will be put on the experimental results for the measured natural frequencies of the generators, perspectives and propositions on subsequent scientific will definitely not be left out

URBAN SOUND RECOGNITION USING DIFFERENT FEATURE EXTRACTION TECHNIQUES

The application of the advanced methods for noise analysis in the urban areas through the development of systems for classification of sound events significantly improves and simplifies the process of noise assessment. The main purpose of sound recognition and classification systems is to develop algorithms that can detect and classify sound events that occur in the chosen environment, giving an appropriate response to their users. In this research, a supervised system for recognition and classification of sound events has been established through the development of feature extraction techniques based on digital signal processing of the audio signals that are further used as an input parameter in the machine learning algorithms for classification of the sound events. Various audio parameters were extracted and processed in order to choose the best set of parameters that result in better recognition of the class to which the sounds belong. The created acoustic event detection and classification (AED/C) system could be further implemented in sound sensors for automatic control of environmental noise using the source classification that leads to reduced amount of required human validation of the sound level measurements since the target noise source is evidently defined

Status and challenges on defense reforms in Bosnia and Herzegovina for Nato integration

Аfter the NATO summit in Bucharest in 2008, the focus of NATO discussions related to further enlargement has been directed towards considering the opportunities for admission of the interested countries from the region of Southeastern Europe. Most of them were countries with an Action Plan for membership in NATO for Southeastern Europe. Bosnia and Herzegovina was one of those countries. At the same time the Bosnia and Herzegovina's integration path to NATO has been set through more dependent scientific variables and indicators which are fundamental foundations for meeting the basic conditions for NATO integration, such as: political, economic and judicial reforms, defense reforms, Interior Ministry, etc. The comprehensive analysis of the defense reforms focused on expenditures of the state's annual budget in relation to the number of armed forces and the needs for progressive increase in the defense budget. In addition, the strategic position of Bosnia and Herzegovina was analyzed and assessed in relation to the following variables: projection of the overall defense forces,internal borders, new types of risks and threats to the national security, deterrence ability and influence on the cohesion of NATO. As a conclusion, an overall numerical assessment of the strategic position was made. Comparison of the defense spending was made with other NATO member states from Southeast Europe, such as the Republic of Slovenia, Croatia and Montenegro. An analysis of the transformation of the number and effectiveness of the Armed Forces of Bosnia and Herzegovina has been made with the countries of Southeast Europe which are NATO members and have approximately the same population, such as the Republic of Croatia and Albania. Research analysis has also been done on Freedom House estimates in order to make an overall analysis and assessment of the fulfillment of the basic criteria for membership of Bosnia and Herzegovina in NATO: political, economic, military and final observations based on numerical parameters for Bosnia and Herzegovina's concluding assessments of the meeting criteria for NATO membership by 2020. Keywords: criteria, challenges, defense reforms, NATO integration, Bosnia and Herzegovin

Personal noise exposure level and the impact on the employee`s performance in the automotive industry

In today’s demanding market environment the companies need to deliver high quality product to their customers and in parallel to maintain an ergonomic workplace for their employees to increase the productivity. The purpose of this paper is determination of the personal noise exposure level caused by the machines and equipment installed in all organization units in an auto part production plant. The noise level was measured and analyzed with noise measurements equipment – dosimeters and software tool at 25 measurement points across the plant. In addition, the strength between the variables, noise levels and concentration, is presented with correlation coefficient

Blade Group Fatigue Life Calculation under Resonant Stresses

The results of the simulations of the blade group resonant stresses in a FE environment and fatigue life calculation are presented in this paper. Numerical calculation for determination of natural frequencies, mode shapes and dynamic stresses, based on FEM and NISA package is used. Analyses are made on the blade group with three blades with rectangular cross section and typical turbine blades with taper, pretwist and asymmetric airfoil as well. The influence of the position of the lacing wire on the resonant stresses is analyzed. Three-dimensional finite element models of the blade group are made by using twenty node isoparametric solid elements. The number of degrees of freedom is different for each model (more than 30000 DOF). The fatigue life and consequent life prediction according the stress load history of the blades is made. The results of the investigation are given in tables and graphics

Воената индустрија и незиното влијание врз настаните во светот

Апстракт: Трговијата со вооружување и воена опрема станува многу профитабилен бизнис, кој забрзано се развива по завршувањето на Втората светска војна, кога се основаат голем број фабрики за производство на вооружување и воена опрема. Од тогаш огромна количина на финансиски средства се вложуваат во развој на воената технологија и за набавка на оружје. Гигантските транснационални компании имаат сè поголемо влијание во светот, што дури во некои земји влијаат и на одлуките на владите. Производството и продажбата на оружје носи исклучително висок профит, што покажува дека во земјата не се произведува оружје само за нивна сопствена употреба,туку укажува и на тоа дека продажбата на оружје станува голем меѓународен бизнис. Транснационалните компании кои произведуваат и продаваат оружје, благодарение на јакото лоби, предизвикуваат воени кризи, и на таков начин ги реализираат своите производи. Голем проблем станува и нелегалната трговија со оружје и воена опрема која носи уште поголем профит, бидејќи таква трговија главно се прави со клиенти на кои меѓународната заедница не им овозможува да купат оружје по законски пат, па токму заради тоа тие се подготвени да платат повеќе отколку што тоа оружје реално чини, а тоа носи екстра профит. Токму на овој начин терористичките организации лесно можат да стигнат до сите видови на оружје кое подоцна се користи за извршување на нивните „цели». Зголемување на бројот на терористички напади ширум светот покажува дека неконтролираниот промет на оружје и воена опрема е сè поголем проблем за меѓународната безбедност. Клучни зборови: воена индустрија, производство, трговија, оружје, конфликти и профи