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

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

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

Autonomous multifunctional vehicle with integrated bio-inspired SMA actuated grasper

The space exploration activities are merging new technologies in order to develop systems challenged to achieve capabilities for high mission experience. Inspired by the numerous applications in space exploration, with the integration of shape memory alloys (SMAs), a 3D printed continuous All Terrain Grasper Transport (AT-GT) vehicle with implemented multi-locomotion grasper was created. In order to reduce failure of the mechanical system, the vehicle is equipped with SMA suspension and SMA tensioner of a pulley system with adaptable height able to achieve movement on a given trajectory and adjust to any terrain. SMA actuators provide controllable actuation based on the simplicity of their design and the shape memory effect. By using the advantages of the origami engineering, soft robotics and smart material implementation, a bio-inspired autonomous grasper was integrated on the AT-GT, capable of leaving the vehicle, grabbing an object and bringing it back to the vehicle. The concept development, the analytical models and the prototype including the benefits of the combined work of the vehicle and the grasper are presented.</p

Analysis of noise impact in urban areas

The exposure of high level of noise in the twenty-first century causes many health problems in the urban areas, which inevitably imposes the need for effective analysis of the noise in order to reduce the noise level and protect the health of the population. One of the major health problems caused by the noise is anxiety that leads to impairment of the quality of life. The city of Skopje, as a large urban area (agglomeration), faces serious problems caused by the environmental noise, which is the reason for various health problems. This research illustrates the methodology for the noise impact analysis in ‘Debar Maalo’ neighborhood. ‘Debar Maalo’ is a neighborhood located in the city centre, surrounded with four major streets, heavy traffic and a lot of people. A survey was conducted on 93 respondents that live, work or are visitors in this area. The results show that the noise has bad influence on the population, so further steps must be taken in order to reduce the noise level in the urban area. This study is a basis for further research about the harmful effects caused by noise, and to find steps to prevent and reduce them. Keywords: environmental noise, subjective analysis, questionnair

Noise exposure level detection using the Skopje.Pulse platform

The intense globalization, the dramatic increase in population and the changes in infrastructure in the large cities have caused a multitude of environmental problems and negative environmental changes in recent years. One of the most worrying problems that occurs in overcrowded and frequent metropolises is the problem of increased noise levels which can greatly affect human health. In the city of Skopje, as the capital of the Republic of North Macedonia, except for a few short-term measurements conducted by state institutions, no other measures have been taken to protect against noise pollution. This paper presents a solution for sustainable noise development and monitoring in the city of Skopje created and implemented by the software company Netcetera for the purpose of 24-hour monitoring of the level of noise in several measuring stations in the city. This concept is based on the “Internet of Things” principle, which collects noise level data via sensor network and Wi-Fi and LoRaWAN communications which are then visualized and monitored online via platform called Skopje Pulse. The first chapter of this paper presents an overview of similar software solutions and ways of collecting data and monitoring the noise level from which the development experience of Skopje Pulse was derived. Furthermore, the second chapter provides a detailed explanation of the platform, sensor network and the way of communication expressed and explained through the concept of "Internet of Things" which was used to develop this solution. The third chapter presents the sensor itself and its specifications. At the end of this paper, data from the sensor network for each day and hour during 2018 are presented, as well as their analysis that identifies the critical and most challenging months, days, and hours with increased noise levels in the City of Skopje as a capital city. Keywords: noise exposure, noise level, IoT, LoRaWAN

Autonomous multifunctional vehicle with integrated bio-inspired SMA actuated grasper

The space exploration activities are merging new technologies in order to develop systems challenged to achieve capabilities for high mission experience. Inspired by the numerous applications in space exploration, with the integration of shape memory alloys (SMAs), a 3D printed continuous All Terrain Grasper Transport (AT-GT) vehicle with implemented multi-locomotion grasper was created. In order to reduce failure of the mechanical system, the vehicle is equipped with SMA suspension and SMA tensioner of a pulley system with adaptable height able to achieve movement on a given trajectory and adjust to any terrain. SMA actuators provide controllable actuation based on the simplicity of their design and the shape memory effect. By using the advantages of the origami engineering, soft robotics and smart material implementation, a bio-inspired autonomous grasper was integrated on the AT-GT, capable of leaving the vehicle, grabbing an object and bringing it back to the vehicle. The concept development, the analytical models and the prototype including the benefits of the combined work of the vehicle and the grasper are presented.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Transport Engineering and Logistic