scholarly journals The Investigation of Insulation Performance Evaluation of the Large Electrical Rotating Machine in Frequency Domain

2020 ◽  
pp. 339-356
Author(s):  
Nattawut Phloymuk ◽  
Masaaki Kando ◽  
Norasage Pattanadech
Keyword(s):  
Electromagnetic Waves ◽  
Thermal Stresses ◽  
Measurement Data ◽  
Interfacial Polarization ◽  
Test Sample ◽  
Depolarization Current ◽  
Ion Migration ◽  
Rotating Machine ◽  
Operation Temperature ◽  
Complex Capacitance

The insulation structure of winding in a large electrical rotating machine consists of epoxy resin and mica material. The insulation structure is composed of many junctions. The insulation problems generate different kinds of signals, such as electromagnetic waves, which may get released from the non-perfect characteristics of the enclosure. This signal may interfere with the functioning of other nearby electronic devices. Therefore, maintaining an excellent condition of the insulation system of the machine is very important. For a condition monitoring of this insulation as proposed in this research, it is taken into consideration the results of the polarization and depolarization current (PDC) measurement of the test sample, and the stator winding rated 13.8 kV was investigated. The experiments were conducted under different thermal stresses, i.e., 25°C (the room temperature) and 100°C (the operation temperature). The test samples were divided into three types: I. haft-overhang, II. overhang and III. full stator bar. From the PDC measurement data record, the complex capacitance and polarization losses (ion migration polarization, slow relaxation polarization and interfacial polarization) were calculated. It was found that the aging of the insulation related to the complex capacitance and polarization losses can be contributed for research in future wireless technology.

scholarly journals Identifying occupant presence in a room based on machine learning techniques by measuring indoor air conditions

2020 ◽  
Vol 172 ◽  
pp. 22005
Author(s):  
Lucia Hanfstaengl ◽  
Michael Parzinger ◽  
Uli Spindler ◽  
Ulrich Wellisch ◽  
Markus Wirnsberger
Keyword(s):  
Machine Learning ◽  
Boundary Conditions ◽  
Heat Dissipation ◽  
Measurement Data ◽  
Test Sample ◽  
Supervised Machine Learning ◽  
Machine Learning Techniques ◽  
Automation System ◽  
Precise Control ◽  
Occupancy Detection

Knowing about the presence and number of people in a room can be of interest for precise control of heating, ventilation and air conditioning. To determine the number and presence of occupants cost-effectively, it is of interest to use already existing air condition sensors (temperature, humidity, CO2) of the building automation system. Different approaches and methods for determining presence have attracted attention in recent years. We propose an occupancy detection method based on a method of supervised machine learning. In an experiment, measurement data were recorded in a research apartment with controllable boundary conditions. The presence of people was simulated by artificial injection of water vapour, CO2 and heat dissipation. The variation of the number of artificial users, the duration of presence and the supply air volume flow of the ventilation resulted in a total of 720 combinations. By using artificial users, the boundary conditions were accurately defined, and different presence situations could be measured time-effectively. The data is evaluated with a method of supervised machine learning called random forest. The statistical model can determine precisely the number of people in over 93% of the cases in a disjoint test sample. The experiments took part in the Rosenheim Technical University of Applied Sciences laboratory.

Combined-Cycle Start-Up Procedures: Dynamic Simulation and Measurement

2016 ◽  
Author(s):  
Nicolas J. Mertens ◽  
Falah Alobaid ◽  
Bernd Epple ◽  
Hyun-Gee Kim
Keyword(s):  
Power Plant ◽  
Dynamic Simulation ◽  
Steam Generator ◽  
Heat Recovery ◽  
Thermal Stresses ◽  
Measurement Data ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Start Up ◽  
Fast Start

The daily operation of combined-cycle power plants is increasingly characterized by frequent start-up and shutdown procedures. In addition to the basic requirement of high efficiency at design load, plant operators therefore acknowledge the relevance of enhanced flexibility in operation — in particular, fast start-ups — for plant competitiveness under changing market conditions. The load ramps during start-up procedure are typically limited by thermal stresses in the heat recovery steam generator (HRSG) due to thick-walled components in the high pressure circuit. Whereas conventional HRSG design is largely based on simple steady-state models, detailed modelling and dynamic simulation of the relevant systems are necessary in order to optimize HRSG design with respect to fast start-up capability. This study investigates the capability of a comprehensive process simulation model to accurately predict the dynamic response of a triple-pressure heat recovery steam generator with reheater from warm and hot initial conditions to the start-up procedure of a heavy-duty gas turbine. The commercial combined-cycle power plant (350 MWel) was modelled with the thermal-hydraulic code Apros. Development of the plant model is based on geometry data, system descriptions and heat transfer calculations established in the original HRSG design. The numerical model is validated with two independent sets of measurement data recorded at the real power plant, showing good agreement.

Materials Testing Fundamentals

2021 ◽  
pp. 1-18
Keyword(s):  
Tensile Testing ◽  
Measurement Data ◽  
Test Sample ◽  
Tensile Tests ◽  
True Stress ◽  
Materials Testing ◽  
Displacement Curve ◽  
Properties Of Materials ◽  
Modulus Of Resilience ◽  
Force Displacement

Abstract Product design requires an understanding of the mechanical properties of materials, much of which is based on tensile testing. This chapter describes how tensile tests are conducted and how to extract useful information from measurement data. It begins with a review of the different types of test equipment used and how they compare in terms of loading force, displacement rate, accuracy, and allowable sample sizes. It then discusses the various ways tensile measurements are plotted and presents examples of each method. It examines a typical load-displacement curve as well as engineering and true stress-strain curves, calling attention to certain points and features and what they reveal about the test sample and, in some cases, the cause of the behavior observed. It explains, for example, why some materials exhibit discontinuous yielding while others do not, and in such cases, how to determine when yielding begins. It also explains how to determine other properties via tensile tests, including ductility, toughness, and modulus of resilience.

scholarly journals An alternative response to the off-shell quantum fluctuations: a step forward in resolution of the Casimir puzzle

2020 ◽  
Vol 80 (9) ◽  
Author(s):  
G. L. Klimchitskaya ◽  
V. M. Mostepanenko
Keyword(s):  
Electromagnetic Waves ◽  
Measurement Data ◽  
Response Functions ◽  
Local Response ◽  
Free Electrons ◽  
Alternative Response ◽  
Local Responses ◽  
Lifshitz Theory ◽  
Principle Of Causality ◽  
Zero Frequency

AbstractThe spatially nonlocal response functions are proposed which nearly coincide with the commonly used local response for electromagnetic fields and fluctuations on the mass shell, but differ significantly for the off-shell fluctuating field. It is shown that the fundamental Lifshitz theory using the suggested response functions comes to an agreement with the measurement data for the Casimir force without neglecting the dissipation of free electrons. We demonstrate that reflectances of the on-shell electromagnetic waves calculated using the nonlocal and commonly employed local responses differ only slightly. The Kramers–Kronig relations for nonlocal response functions possessing the first- and second-order poles at zero frequency are derived, i.e., the proposed response satisfies the principle of causality. An application of these results to resolution of the Casimir puzzle, which lies in the fact that the Lifshitz theory is experimentally consistent only with discarded dissipation, is discussed.

scholarly journals Experimental Investigation of Electro-thermal Stress Impact on SiC-BJTs Electrical Characteristics

2013 ◽  
Vol 2013 (HITEN) ◽  
pp. 000290-000297
Author(s):  
Thibaut Chailloux ◽  
Cyril Calvez ◽  
Pascal Bevilacqua ◽  
Dominique Planson ◽  
Dominique Tournier
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Room Temperature ◽  
Thermal Stresses ◽  
Temperature Cycling ◽  
Bipolar Junction Transistors ◽  
Electrical Characteristics ◽  
Switching Operation ◽  
Operation Temperature ◽  
The Stability

The aim of this study consists in investigating the effects of electrical and thermal stresses on SiC n-p-n bipolar junction transistors (BJTs). The stability of the electrical characteristics of BJTs is inspected under switching operation, DC operation, temperature cycling and continuous thermal stress up to 225°C. While switching operation and temperature cycling for several hours lead to significant changes at 25°C, the electrical characteristics were little degraded at high temperature. Besides, DC operation and continuous thermal stress did not result in significant degradation at all, both at room temperature and at high temperature.

scholarly journals Analysis and Simulation of Forcing the Limits of Thermal Sensing for Microbolometers in CMOS–MEMS Technology

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 733
Author(s):  
Hasan Göktaş ◽  
Fikri Serdar Gökhan
Keyword(s):  
Joule Heating ◽  
Thermal Stresses ◽  
Thermal Sensitivity ◽  
High Sensitivity ◽  
Low Noise ◽  
Night Vision ◽  
Small Scale ◽  
Operation Temperature ◽  
Stiffness Constant ◽  
Mems Technology

Room-temperature highly sensitive microbolometers are becoming very attractive in infrared (IR) sensing with the increase in demand for the internet of things (IOT), night vision, and medical imaging. Different techniques, such as building extremely small-scale devices (nanotubes, etc.) or using 2D materials, showed promising results in terms of high sensitivity with the cost of challenges in fabrication and low-noise readout circuit. Here, we propose a new and simple technique on the application of joule heating on a clamped–clamped beam without adding any complexity. It provides much better uniformity in temperature distribution in comparison to conventional joule heating, and this results in higher thermal stresses on fixed ends. This consequently brings around 60.5× improvement in the overall temperature sensitivity according to both theory and COMSOL (multiphysics solver). The sensitivity increased with the increase in the stiffness constant, and it was calculated as 134 N/m for a device with a 60.5× improvement. A considerable amount of decrease in the operation temperature (36× below 383 K and 47× below 428 K) was achieved via a new technique. That’s why the proposed solution can be used either to build highly reliable long-term devices or to increase the thermal sensitivity.

scholarly journals Perspectives on Cathodes for Protonic Ceramic Fuel Cells

2021 ◽  
Vol 11 (12) ◽  
pp. 5363
Author(s):  
Glenn C. Mather ◽  
Daniel Muñoz-Gil ◽  
Javier Zamudio-García ◽  
José M. Porras-Vázquez ◽  
David Marrero-López ◽  
...  
Keyword(s):  
Fuel Cells ◽  
Noble Metals ◽  
Electrical Energy ◽  
Composite Electrodes ◽  
Ion Migration ◽  
Conducting Oxides ◽  
Operation Temperature ◽  
Ceramic Fuel ◽  
Ceramic Fuel Cells ◽  
Electronic Conductors

Protonic ceramic fuel cells (PCFCs) are promising electrochemical devices for the efficient and clean conversion of hydrogen and low hydrocarbons into electrical energy. Their intermediate operation temperature (500–800 °C) proffers advantages in terms of greater component compatibility, unnecessity of expensive noble metals for the electrocatalyst, and no dilution of the fuel electrode due to water formation. Nevertheless, the lower operating temperature, in comparison to classic solid oxide fuel cells, places significant demands on the cathode as the reaction kinetics are slower than those related to fuel oxidation in the anode or ion migration in the electrolyte. Cathode design and composition are therefore of crucial importance for the cell performance at low temperature. The different approaches that have been adopted for cathode materials research can be broadly classified into the categories of protonic–electronic conductors, oxide-ionic–electronic conductors, triple-conducting oxides, and composite electrodes composed of oxides from two of the other categories. Here, we review the relatively short history of PCFC cathode research, discussing trends, highlights, and recent progress. Current understanding of reaction mechanisms is also discussed.

scholarly journals Ionic Transportation and Dielectric Properties of YF3:Eu3+ Nanocrystals

Nanomaterials ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 995 ◽  
Author(s):  
Xiaoyan Cui ◽  
Tingjing Hu ◽  
Jingshu Wang ◽  
Junkai Zhang ◽  
Xin Zhong ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Dielectric Properties ◽  
Carrier Transport ◽  
Low Frequency ◽  
Interfacial Polarization ◽  
Structural Disorder ◽  
Ion Diffusion ◽  
Ion Migration ◽  
Conductivity Increase ◽  
The Difference

The ionic transportation and dielectric properties of YF3:Eu3+ nanocrystals are investigated by AC impedance spectroscopy. The ion diffusion coefficient and conductivity increase along with the doping concentration and reach their highest values at 4% of Eu3+. The difference of ionic radius between Eu3+ and Y3+ leads to the structural disorder and lattice strain, which deduces the increase of the ion diffusion coefficient and conductivity before 4% Eu3+ doping; then the interaction of the neighboring doping ions is dominated, which results in the difficulty of ion migration and decreases of the ion diffusion coefficient and conductivity. The strong dispersion of the permittivity in the low frequency region indicates that the charge carrier transport mechanism is the ion hopping in the system. The low-frequency hopping dispersion is affected by an interfacial polarization, which exhibits a Maxwell-Wagner relaxation process, and its loss peak shifts to higher frequency with the ionic conductivity increasing.

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