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Badania eksperymentalne słupów CFST z betonem zwykłym i ekspansywnym
PublicationPraca przedstawia badania eksperymentalne ponad 40 słupów CFST. Analizie poddano wyniki siły niszczącej słupy w aspekcie grubości stalowego płaszcza, smukłości słupa, rodzaju betonu wypełniającego stalową rurę (zwykły i ekspansywny) i jego wytrzymałości a także sposobu obciążania słupa (przez rdzeń lub przez cały przekrój). Sprawdzono efektywność słupów CFST z użyciem betonu ekspansywnego i zwykłego rozumianą jako stosunek nośności...
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Extended duration running and impulse loading characteristics of an acoustic bearing with enhanced geometry
PublicationThis paper presents performance during prolonged running of the acoustic bearing when PZTs are switched off and when they are switched on. The effect of active PZT on shaft’s displacements in X and Y directions is clearly demonstrated. Performance of the acoustic bearing was also assessed when an impulse force was applied to the running shaft at speed. Once again the benefits of having PZTs active are beyond doubt. The instability...
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Field Tests on Hydrodynamic and Hybrid Operation of a Bidirectional Thrust Bearing of a Pump-Turbine
PublicationIn vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Due to the bidirectional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The...
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Field tests on hydrodynamic and hybrid operation of a bi-directional thrust bearing of a pump-turbine
PublicationIn vertical shaft pump turbines operating in pumped storage power plants an important role is played by a thrust bearing. Because of bi-directional character of operation, thrust bearing tilting pads have to be supported symmetrically, which is known to be unfavourable from the point of view of their performance. Large thrust bearings have to be carefully designed so as to minimise excessive thermo-elastic pad deformations. The...
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Study of the Influence of Heat Convection Coefficient on Predicted Performance of a Large Tilting-Pad Thrust Bearing
PublicationPart of the heat generated by the shearing of the lubricating film during operation of a hydrodynamic bearing is transferred to the bearing components. In the case of the pad, which is usually fully submerged in the lubricating oil, heat is further transferred at the pad free walls to the oil by convection. This mechanism causes a thermal gradient in a pad and, consequently, its thermal deflection. In large hydrodynamic thrust...
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ANALYSIS OF THE POSSIBILITIES OF HIGH SPEED SHAFT BEARING SYSTEM DURABILITY INCREASE
PublicationDuring the operation of wind turbines with a gearbox of traditional configuration, a high failure rate of high-speed shaft bearings is observed. Such a high failures frequency is not reflected in standard bearing durability calculation methods, which can be attributed to atypical failure mechanism. To avoid observed problems in the 1.5 MW wind turbine, the modification of the existing bearing system is proposed. Multiple options,...
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Influence of bush wear in water lubricated marine stern tube bearings with shaft misalignment
PublicationWater lubricated propeller shaft bearings are frequently employed on modern ships due to their advantages such as durability, simplicity and low price. Specific working conditions on ships cause shaft misalignment which often results in rapid wearing of bush and shaft. Shaft misalignment could be an effect of manufacturing or assembly faults but sometimes it appears due to hull or shaft deformation. The wearing process has influence...
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THE SYNCHROSQUEEZING METHOD IN BEARING ESTIMATION OF STATIONARY SIGNALS FOR PASSIVE SONAR WITH TOWED ARRAY
PublicationIn this paper, a novel method of bearing estimation in a passive sonar system with a towed array is introduced. The classical approach of bearing estimation based on the spatial spectrum [1] is extended by using the synchrosqeezing method that is a part of the reassignment method introduced by Kodera et al. [2]. Using this method leads to a precise bearing estimation. The proposed method requires a relatively small amount of computation,...
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Environmentally acceptable lubricants (EAL) compared with a reference mineral oil as marine stern tube bearing lubricant – Experimental and theoretical investigations
PublicationThe purpose of this research is to indicate the potential differences in bearing characteristics resulting from the application of different lubricant types with the same viscosity grade. The effect of different environmentally acceptable lubricants (EALs) on hydrodynamic journal bearing properties is studied experimentally and compared to the properties obtained after lubrication with a reference mineral oil. The results of the...
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TRANSFER OF ELECTRIC ENERGY [2023/24]
e-Learning CoursesCourse content: Basic information on the structure of the power system, the major devices (components) for generation, transmission and distribution of electricity. Active and reactive power generation and their sources. Power supply networks. Tasks, structure, parameters. AC and DC transmission of electricity. Equivalent diagrams of the components of the power system. Steady state load flow calculation: currents, voltage,...
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TRANSFER OF ELECTRIC ENERGY [2022/23]
e-Learning CoursesCourse content: Basic information on the structure of the power system, the major devices (components) for generation, transmission and distribution of electricity. Active and reactive power generation and their sources. Power supply networks. Tasks, structure, parameters. AC and DC transmission of electricity. Equivalent diagrams of the components of the power system. Steady state load flow calculation: currents, voltage,...
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TRANSFER OF ELECTRIC ENERGY [2024/25]
e-Learning CoursesCourse content: Basic information on the structure of the power system, the major devices (components) for generation, transmission and distribution of electricity. Active and reactive power generation and their sources. Power supply networks. Tasks, structure, parameters. AC and DC transmission of electricity. Equivalent diagrams of the components of the power system. Steady state load flow calculation: currents, voltage, power,...
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TRANSFER OF ELECTRIC ENERGY [2024/25]
e-Learning CoursesCourse content: Basic information on the structure of the power system, the major devices (components) for generation, transmission and distribution of electricity. Active and reactive power generation and their sources. Power supply networks. Tasks, structure, parameters. AC and DC transmission of electricity. Equivalent diagrams of the components of the power system. Steady state load flow calculation: currents, voltage,...
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The influence of polymer bearing material and lubricating grooves layout on wear of journal bearings lubricated with contaminated water
PublicationThe goal of the present paper is to investigate wear properties of journal sliding bearing operating in the conditions of contaminated water lubrication. Several bearing materials and bearing sleeve designs (differing in the axial grooves position and their shape) were tested experimentally under typical operating conditions in a dedicated test rig, which was equipped with a lubricating system, enabling lubrication with contaminated...
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Numerical analysis on axial capacity of steel built-up battened columns
PublicationThis paper deals with the numerical analysis aimed at study the bearing capacity of pinended steel built-up columns under axial compression. Finite element (FE) models were performed for the columns presented in the literature. The main problem discussed in the article is the shape and magnitude of geometric imperfections introduced into the numerical FE model, necessary to obtain the load capacity consistent with the experimental...
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STABILITY ANALYSIS OF A TRUSS WITH SLOPING ELASTIC BRACES
PublicationSteel trusses have a much greater strength and stiffness in their plane than out of their plane, and therefore should be braced against lateral deflection and twisting. Such elements like purlins apart from bearing vertical load are part of bracing that stabilize roof trusses against distortional buckling. The stability of trusses with elastic bracing was investigated in an experimental research. Braces situated at some angle measured...
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Compliance tests of the polymer layers used as hydrodynamic bearing coatings
PublicationOperational experience and scientific investigations results showed that polymer lined hydrodynamic bearings can withstand more severe operating conditions compared than white metal bearings. PTFE and PEEK-based coatings are the most frequently used as Babbitt alternatives. Both polymers differ significantly from the each other in material properties. According to catalogue data compression modulus of PTFE, it is about an order...
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Some problems of slide bearing material fatigue evaluation.
PublicationA slide bearing alloy resistance against fatigue failures have been investigated for three different lubricants, different heat loadings and different stress ratio κ values. The research methods and data handling procedures for determination of particular parameter effects on fatigue strength have been described and analysed for experiments that were set and performed in laboratory tester SKMR-2. Main and interaction effects of...
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Reliability model of slide bearings with particular attention given to lubricating oil
PublicationThe paper presents the slide bearing with circulating lubrication as a system of series three-element structure, where lubricating oil is the weakest link. In accordance with the Pierce statement that ''strength of chain is the strength of its weakest link'', a bearing reliability model has been developed. It allows to use the lubricating oil to evaluate the probability of correct working of the whole slide bearing, i.e. the reliability....
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Vibro piles performance prediction using result of CPT
PublicationVibro piles belong to the group of full displacement piles with an expanded base, characterised by a very high load capacity, especially in non-cohesive soils. The problem is to adopt a reliable method for the determination of full load–settlement (Q–s) curve. A frequent difficulty is the determination of the load capacity limit based on the static load test because the course of the load–settlement curve is of a linear nature....
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The buckling analysis of a cold-formed steel C-sectional column resting on an elastic foundation
PublicationThe paper is focused on stability analysis of different models of steel cold-formed C-section column. The analysed element may be applied as a primary load-bearing member in steel trusses or silo columns. The column can be used as a support for a wall of roof plates made of corrugated sheets. The wall sheeting that restrains the column against buckling may be considered as an elastic foundation. Due to the design solutions the...
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Effect of the Presence of the Lifting Pocket on The THD Performance of a Large Tilting-Pad Thrust Bearing
PublicationIn this paper, an attempt was taken to study the effect of the lifting pocket on THD performance of a large tilting-pad thrust bearing of Itaipu power plant. B3earing performance was evaluated including recess shape for several cases of its depth. The results show, that hydrostatic recess changes calculated bearing properties quite significantly, especially in the vicinity of the pocket
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Water-lubricated stern tube bearing - experimental and theoretical investigations of thermal effects
PublicationThe paper presents research results of thermal phenomena accompanying operation of a water-lubricated stern tube bearing with axial grooves. Experimental tests revealed, that intensity of forced axial flow has strong influence on bush temperature. Numerical simulations focused on investigation of the thermal phenomena under operation of water-lubricated journal bearing showed, that restricted axial flow promotes backflow of the...
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Azo group(s) in selected macrocyclic compounds
PublicationAzobenzene derivatives due to their photo- and electroactive properties are an important group of compounds finding applications in diverse fields. Due to the possibility of controlling the trans–cis isomerization, azo-bearing structures are ideal building blocks for development of e.g. nanomaterials, smart polymers, molecular containers, photoswitches, and sensors. Important role play also macrocyclic compounds well known for...
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Water-Lubricated Sintered Bronze Journal Bearings—Theoretical and Experimental Research
PublicationWater lubricated bearings are used from many years in shipbuilding, hydro power and other industries because of their advantages such as: extensive serviceable life, low coefficient of friction, longevity of shaft sleeve, good abrasion resistance, low maintenance required, unit simplicity, no danger of pollution and low price. Various types of water lubricated sliding bearings have been tested at the Technical University of Gdansk...
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Biocompatibility and bioactivity of bearing loaded metallic implants
PublicationPresentation of developed titanium alloy base composite materials possessing better biocompatibility, longer lifetime and bioactivity behavior for bearing loaded implants, e.g. hip joint and knee joint endoproshtesis.
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Analysis of Failures of High Speed Shaft Bearing System in a Wind Turbine
PublicationDuring the operation of wind turbines with gearbox of traditional configuration, consisting of one planetary stage and two helical stages high failure rate of high speed shaft bearings is observed. Such a high failures frequency is not reflected in the results of standard calculations of bearing durability. Most probably it can be attributed to atypical failure mechanism. The authors studied problems in 1.5 MW wind turbines of...
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Improving the accuracy of bearing in active sonar with cylindrical array using spectrum estimation.
PublicationThe articles presents a method for improving the accuracy of bearing in multibeam sonar with a cylindrical array. Based on a known spatial spectrum estimation technique, the method has been successfully used in linear array systems. Its accuracy of bearing is satisfactory and ensures a relatively low computational effort. The article discusses certain simplifications and assumptions to adapt the spatial spectrum estimation technique...
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Tribological model of porous bearings with particular attention given to the lubricant lubricity
PublicationThe friction and wear problems, accompanying all the tribological systems, lead to reduced service life. In order to prevent such situation, it is necessary to maintain fluid friction, which improves durability of all friction nodes in a tribological system. In the paper, the tribological system consists of porous bearings and the model deals with their weakest spots - the oil outflow points in the porous wall. A kinetic model...
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Field investigation of low-temperature cracking and stiffness moduli on selected roads with conventional and high modulus asphalt concrete
PublicationHigh Modulus Asphalt Concrete (HMAC) was introduced in Poland as a one of the solutions to the problem of rutting, type of deterioration common in the 1990s. After first encouraging trials in 2002 HMAC was widely used for heavily loaded national roads and motorways. However some concerns were raised about low-temperature cracking of HMAC. This was the main reason of the studies presented in this article were started. The article...
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Intelligent microbearing project with memory of stress-strain history
PublicationTaking into account the increasing need of intelligent micro-bearing with memory, this paper presents the optimization, simulation and practical application of operating parameters(load carrying capacity, friction forces, friction coefficient, wear), simulation for hydrodynamic HDD micro-bearing with curvilinear nano-grooved journal profile. One of the reason of such journal profile is that this journal profile contributes to the...
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Experimental comparison of the transition speed of a hydrodynamic journal bearing lubricated with oil and magnetorheological fluid
PublicationA journal bearing test bench is used to find the transition speed between the hydrodynamic and mixed lubrication regimes for a modified magnetorheological (MR) fluid. It is shown that the transition speed of the bearing can be reduced by applying a local magnetic field near minimum film when it is lubricated with the MR fluid, and that this will only marginally increase friction. The lubricating performance of the MR fluid is compared...
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RESEARCH ON HYDRODYNAMIC PEEK JOURNAL BEARINGS LUBRICATED WITH WATER AND OIL
PublicationThe main purpose of the research was to determine the possibilities and experimentally test the benefits of replacing conventional oil lubrication with ecological water lubrication. Tests were carried out on a test rig for hydrodynamic radial bearings under conditions representative of the expected applications for the bearing in water turbines. Bearings made from the polymer material PEEK (polyether ether ketone) were tested under static...
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Influence of e-beam irradiation on poly(aliphatic/aromatic-ester) multiblock copolymers used as biomaterials
PublicationThe use of polymers became more relevant in medical applications for the versatility in processing and enhanced material properties of polymers. In order to be suitable as a biomaterial, it is of medical importance that these polymers are biocompatible and do not elicit negative responses from the body after implantation. Furthermore during the course of usage under load-bearing conditions, these biomaterials must sustain dynamical...
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Reducing common mode voltage and bearing currents in quasi - resonant DC - link inverter
PublicationIn the paper, a concept of separation of an inverter-fed induction motor drive from its mains supply by two transistor switches inserted in the dc-link circuit is reexamined based on the proposed parallel quasi-resonant dc-link inverter (PQRDCLI). The objective of the paper is to show an advantage of the proposed topology in limiting high frequency common mode voltage and bearing currents. In the laboratory setup, an induction...
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Running characteristics of aerodynamic bearing with self-lifting capability at low rotational speed
PublicationAn aerodynamic journal bearing that is capable of self-generating squeeze-film pressure is presented and its dynamic characteristics investigated numerically and experimentally. A numerical method based on a time marching static model was applied to assess the orbit trajectory path of the rotor upon a perturbation. Experimental results were obtained to validate the effect of the self- generated squeeze-film pressure on the stability...
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Bearing capacity of working platform using distinct layout optimization method
PublicationBearing capacity of the working platforms from sandy soil resting on NC and OC clays was analyzed using LimitState GEO program. Different failure modes are considered using distinct layout optimization (DLO) method, which forms the upper bound solution of limit state analysis. Different mechanisms of failure were observed as a function of the platform thickness, angle of internal friction of the platform material and undrained...
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High-precision bearing estimation for active sonar with cylindrical array performed by interpolated array transformation
PublicationThe article presents a method for improving the accuracy of bearing in multibeam sonar with a cylindrical array. The antenna’s non-linear shape and the resulting non-uniform sampling of the signal in space, mean that known methods of high-resolution spectral analysis cannot be used. In order to apply an algorithm from this group, a linear virtual antenna must be produced. The paper presents a technique of mapping a cylindrical...
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Investigation of the thermal effects in water-lubricated journal bearings with axial grooves
PublicationWater-lubricated hydrodynamic journal bearings are frequently applied as stern tube bearings due to their advantages over other bearing types. They are environmentally friendly, can operate without sealings and in conditions of low friction losses. The most popular are bearings with open axial grooves, which require, for proper operation, forced axial flow of the lubricating water. Correctly designed and operated stern tube bearings...
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Establishing Relationships between Parameters of the controlled Compaction Soil by Using Various In-Situ Tests
PublicationThe aim of research was evaluating reliable correlations between chosen soil parameters describing state of surface layers of soil. The paper presents site comparative tests based on the light falling weight deflectometer (LFWD), the static plate load tester (VSS), the dynamic probing light tester (DPL) and the bearing ratio tester (CBR in-situ) with relationships between soil state parameters. All featured in-situ...
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The use of plate springs for preloading of a system of tapered roller bearings of a wind turbine gearbox
PublicationThe use of preloaded tapered roller bearings in wind turbine drive systems allows a transfer of load in the case of high variations of axial forces. The examined bearing system, a modification of a current design, consists of a pair of different sized bearings. Previous study showed the high sensitivity of tapered roller bearings on the existing radial interference. Dimensional tolerances used in the original design do not allow...
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Synthesis, Molecular Structure, Anticancer Activity, and QSAR Study of N-(aryl/heteroaryl)-4-(1H-pyrrol-1-yl)Benzenesulfonamide Derivatives
PublicationA series of N-(aryl/heteroaryl)-4-(1H-pyrrol-1-yl)benzenesulfonamides were synthesized from 4-amino-N-(aryl/heteroaryl)benzenesulfonamides and 2,5-dimethoxytetrahydrofuran. All the synthesized compounds were evaluated for their anticancer activity on HeLa, HCT-116, and MCF-7 human tumor cell lines. Compound 28, bearing 8-quinolinyl moiety, exhibited the most potent anticancer activity against the HCT-116, MCF-7, and HeLa cell lines,...
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Experimental study on the feasibility of alternative materials for tilting pad thrust bearings operating in transition to mixed friction
PublicationIn hydrodynamic bearings traditional bearing alloys: Babbitts and bronzes are most frequently utilized. Polymer sliding layers are sometimes applied as a valuable alternative. Hard diamond-like carbon (DLC) coatings, which are also considered for certain applications may show some advantages, as well. Although material selection is of secondary importance in a full film lubrication regime it becomes important in mixed friction...
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Current-based higher-order spectral covariance as a bearing diagnostic feature for induction motors
PublicationConducting the diagnosis of induction motors remotely by analyzing the supply current is an attractive prospect with the lack of access to the engine. Currently, there is no solution, based on analysis of the current, the credibility of which would allow its use in industry. The statistics of bearing failures in induction motors indicate that they constitute more than 40% of induction motor damage, therefore, bearing diagnosis...
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Effect of manufacturing errors of the pad sliding surface on the performance of the hydrodynamic thrust bearing
PublicationIn the present study, investigation of the effect of manufacturing errors on the performance of large tilting pad thrust bearings has been performed, following a CFD-based Thermohydrodynamic analysis of a single pad. A 3D model has been generated, including the pad, the lubricant film and the corresponding part of the collar. The pad has been assumed to be deformed about the pivot point, due to thrust loading. Manufacturing errors...
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THEORETICAL AND EXPERIMENTAL INVESTIGATION OF THIN-WALLED BEARING SHELL’S DESIGN PARAMETERS AND ASSEMBLY CONDITIONS ON THE HOLDING TORQUE INSIDE A HOUSING BORE OF A CONNECTING ROD
PublicationThe aim of the work was the experimental and theoretical evaluation of the influence of the most important parameters determining the holding torque of a thin-walled bearing shell inside a housing bore of a connecting rod. The main investigated parameters were defned by authors experience in this feld. In the frst stage of research, a special test stand was designed in order to allow measuring the real values of the friction torque...
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Numerical modelling and experimental verification of compressible squeeze film pressure
PublicationThe validity of using the Reynolds equation for compressible squeeze film pressure was tested with computational fluid dynamics (CFD). A squeeze film air bearing was instrumented with pressure sensors and non-contacting displacement probes to provide transient measurements of film thickness and pressure. The film thickness measurements also provided input parameters to the numerical prediction. However, numerical results showed...
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Common-Mode Voltage and Bearing Currents in PWM Inverters: Causes, Effects and Prevention
PublicationIn modern induction motor drives an increase of transistors' switching frequency and a decrease of switching times are the sources of some serious problems. The high dv/dt and the common mode voltage generated by the inverter PWM control results in the appearances of bearing currents, shaft voltages, motor terminal overvoltages, the decrease of motor efficiency, and electromagnetic interference. The aspects of common mode (CM)...
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Normal stress distribution in built‑up cold‑formed column in relation to interconnecting bolt spacing
PublicationIn order to increase a stiffness of cold-formed steel (CFS) elements it is practised to built-up the cross-section. In the analysed case, a main element is strengthened by adding extra chord in contact partially along the column. This additional chord acts as a longitudinal stiffener connected with the main section by series of bolts. Authors check whether rules applied over the years, for hot-rolled elements, can be indiscriminately...
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Experimental Testing of Innovative Cold-Formed "GEB" Section / Badania Eksperymentalne Innowacyjnego Kształtownika Giętego Na Zimno Typu „Geb“
PublicationOne of the major advantages of light gauge steel structures made of cold-formed steel sections is their low weight, so manufacturers are increasingly using the possibilities of those sections for the production of typical single-storey steel structures systems. Well known profiles, such as Z, C and the so called hat sections that have been studied and described in the literature, are used mainly as purlins or truss components....