Iskanje po katalogu digitalne knjižnice

Opis: When a fault occurs in a power transmission system, voltages that are dangerous to people may occur. The aim of this work is to present the following method of protection: the use of protective foil installed at the appropriate depth around the transmission pole. Moreover, a procedure is presented for determining the optimal size of the protective film using a minimum number of finite element method calculations. In addition to the finite element method, evolutionary methods are used to determine the appropriate coefficients. Real earthing system data, earth data, and the fault current are obtained from the Slovenian system operator (ELES, d.o.o.) and used exclusively in the presented analyses. The results of determining the appropriate size of the protective foil for two transmission poles are presented, and the determination of the required breakthrough strength of the materials used is shown. The suitability of the proposed method is confirmed. This method is practical and useful when protection with protective foil is required, ensuring only as much as necessary is applied.
Ključne besede: transmission system, touch voltage, touch voltage, step voltage, grounding system, differential evolution, artificial bee colony, teaching–learning-based optimization
Objavljeno v DKUM: 23.04.2025; Ogledov: 0; Prenosov: 1
Celotno besedilo (29,51 MB)

Opis: A new approach using a horizontally layered analytical soil model for inhomogeneous soil is presented. The presented approach also considers deeper soil layers, which is not the case when simply dividing the area of interest into smaller subareas. The finite element method model was used to prepare test data because, in such a case, the soil parameters are known. Six lines simulating Wenner’s method were used, and their results were combined appropriately to determine the soil parameters of nine subareas. To determine the soil parameters in the scope of each subarea, different optimization methods were used and compared to each other. The results were analyzed, and Artificial Bee Colony was selected as the most appropriate method among those tested. Additionally, the convergence of the methods was analyzed, and Memory Assistance is presented, with the aim of shortening the calculation time. In this study, three-, four-, five-, and six-layered soil models were tested, and it is concluded that the three-layered model is most appropriate. A finite element method model based on the soil determination results was constructed to verify the results. The results of the Wenner’s method simulation in the cases of the test data and final model were compared to confirm the accuracy of the presented method
Ključne besede: grounding system, soil model, finite element method, differential evolution, artificial bee colony, teaching–learning-based optimization
Objavljeno v DKUM: 21.02.2025; Ogledov: 0; Prenosov: 3
Celotno besedilo (6,81 MB)

Opis: Diplomsko delo obravnava rekonstrukcijo valjčne proge 800 v podjetju Štore Steel, ki jo je izvedlo podjetje ETRA, d. o. o. V osnovi gre za krmiljenje asinhronskih motorjev, ki so ostali nespremenjeni od začetka delovanja proge. Proga 800 uporablja 16 asinhronskih motorjev, pri čemer je prvotno en pretvornik krmilil osem asinhronskih motorjev (pretvornik ASEA tip »YRYB«), tj. pretvornik ASEA tip »YRYB«, ki je bil v uporabi ob zagonu stroja. Pretvornik ASEA tip »YRYB« je bil sprva najustreznejša rešitev, nato pa se je pojavila težava z vzdrževanjem, saj je bila elektronika draga in težavna za pridobiti, predvsem zaradi pomanjkanja rezervnih delov. Prva faza prenove je vključevala postopno demontažo obstoječih pretvornikov ASEA in namestitev pretvornikov SIMOVERT MASTERDRIVES Vector Control. Ta izvedba je težavna za vzdrževanje, saj če odpove samo en segment (DC-link), so štirje motorji v napaki. Kljub temu da je ta izvedba težavna za vzdrževanje, je bila v tistem času najboljša možna rešitev. Prav zaradi tega je sledila nadaljnja zamenjava za Sinamics S120, ki krmili štiri asinhronske motorje. Ta izvedba je prav tako predstavljala izzive za vzdrževanje, saj je odpoved enega segmenta (DC-link) povzročila napako pri štirih asinhronskih motorjev, podobno kot pri SIMOVERT MASTERDRIVES Vector Control. Končna faza prenove je vključevala uporabo pretvornikov Sinamics G120C. Vsak asinhronski motor je dobil svoj pretvornik, kar je omogočilo izboljšano vzdrževanje in boljšo diagnostiko. Morebitna okvara enega pretvornika ni več vplivala na celotno proizvodnjo in proizvodni proces. Delo prav tako podrobno opisuje postopek optimizacije pretvornika Sinamics G120C z uporabo programskega orodja STARTER.
Ključne besede: asinhronski motor, optimizacija, regulacija, Siemens Sinamics G120C, Štore Steel
Objavljeno v DKUM: 01.07.2024; Ogledov: 265; Prenosov: 92
Celotno besedilo (7,33 MB)

Opis: Recently, an increasing number of electromagnetic devices have been using smart fluids. These include ferrofluids, electrorheological fluids, and magnetorheological (MR) fluids. In the paper, magnetorheological fluids are considered for use in a spherical actuator for haptic applications. An approach is presented to the design and optimization of such a device, using finite element method modelling linked with differential evolution (DE). Much consideration was given to the construction of the objective function to be minimized. A novel approach to objective function assembly was used, using reference values based on the model design and created with parameters set to the midpoint values of the selected range. It was found to be a useful strategy when the reference values are unknown. There were four parameters to be optimized. Three of them gravitated towards the boundary value, and the fourth (actuator radius) was somewhere in between. The value of the objective function reached a minimum in the range of actuator radius between 42.9880 mm and 45.0831 mm, which is about a 5% difference in regard to the actuator radius. Three passes of optimization were performed with similar results, proving the robustness of the algorithm.
Ključne besede: magnetorheological fluid, finite element method, FEM, optimization, differntial evolution, DE, actuator
Objavljeno v DKUM: 22.05.2024; Ogledov: 173; Prenosov: 22
Celotno besedilo (4,69 MB)
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Opis: Currently, meeting the new fuel consumption and emissions standards is the biggest challenge in the automotive industry. One of the solutions is hybridization of the vehicle’s powertrain. This brings with it larger complexity of the vehicle control unit and its pre-calibration. This thesis explores gear shift map and load point shift map, which are two pre-calibration maps included in the vehicle control unit. More specifically it delves in to how the pre-calibration maps are created and how changing their parameters impacts the fuel consumption of the vehicle. Algorithms and optimization simulations were created and performed using AVL’s tool called the Powertrain system optimizer (PSO) which was created within the MATLAB software.
Ključne besede: Hybrid electric vehicle, Hybrid powertrain, Gear shift map, Load point shift map, Pre-calibration.
Objavljeno v DKUM: 23.11.2023; Ogledov: 393; Prenosov: 0