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Svet interneta stvari postaja vse bolj priljubljen, saj nam olajša vsakodnevna opravila. Pri tem lahko nastanejo velike množice podatkov in z njimi potreba po njihovi obdelavi in analizi, kjer nam lahko področje strojnega učenja dodatno razširi funkcionalnost sistemov. Hkrati pa tovrstna tematika vse pogosteje postaja del industrijskih obratov, kjer sta hitrost in kakovost obdelave primarna vidika. Namen izbrane diplomske naloge je meritev in analiza električnega toka električnega mešalnika za hrano ter posledično napoved vsebine naprave s pomočjo metod strojnega učenja. Električni mešalnik je pri tem zgolj poceni in praktičen nadomestek pravih industrijskih naprav. Izvedli smo več meritev posameznih vhodnih sestavin mešalnika, ki smo jih kasneje uporabili v štirih metodah strojnega učenja. Metodam smo nato ovrednotili čas izvajanja in natančnost napovedovanja. Pogosto smo uspeli napovedati stanje naprave, a smo opazili največ težav pri napovedovanju vhodnih sestavin, ki so bile po gostoti oziroma viskoznosti najbolj podobne. The world of IoT is becoming increasingly popular as it makes everyday tasks easier but can lead to large data sets. We need to process and analyze the obtained data, and this is where the field of machine learning can further extend the functionality of our systems. At the same time, IoT and machine learning are becoming part of industrial plants, where speed and quality of processing are primary considerations. The aim of this diploma thesis is to measure and analyze the electric current of an electric food mixer and predict the content of the device using machine learning algorithms. An electric mixer is merely a cheap and practical substitute for real industrial devices. We conducted several measurements of individual input ingredients of the mixer, which were subsequently used in four machine learning methods. The methods were then evaluated for their execution time and prediction accuracy. While we were often able to accurately predict the state of the device, we observed the greatest difficulty in predicting input ingredients that were most similar in density or viscosity.

The authors describe electrical resistivity method using a laboratory experiment, which was conducted in order to calculate the percentage of current that penetrated each layer of soil arranged in a container using Schlumberger array. Four soil samples arranged in three different set-ups were used. The apparent resistivity obtained was interpreted using curve matching techniques and WinResist iteration yielding types A curve, H curve and A curve, respectively. The interpreted data gave the resistivity of each layer and its thicknesses. The thicknesses obtained from the interpretation were at variance with the actual thicknesses arranged in the container. A multiplier was obtained which serves as a constant in other to obtain the actual thickness. The effective penetration depth of current was determined through the calculated thickness of each layer and the known electrode spacing (AB). The percentage of current that penetrates the layers was found to depend on the electrode spacing as well as the thickness of that layer. Thus, a layer with relatively small thickness has a small percentage of current passing through it compared to a thicker layer.

This study focuses on the wear, friction and electrical characteristics of the newly developed, disc-disc contact design for sliding electrical contacts. Different types of graphite and copper, as the material combinations, different contact operating variables and, in particular, different directions of the electrical current, i.e., the disc polarity, were investigated under real contact conditions in a dedicated tribological test rig. The electrographite and polymer-bonded graphite were running in a self-mated contact, against copper and against each other. The polymer-bonded-graphite/polymer-bonded-graphite pair performed the best for almost all the studied parameters, while the mixed, dissimilar, polymer-bonded-graphite/electrographite combination had the worst performance. Moreover, all the pairs containing electrographite material exhibited unstable contact behaviour, and generally gave a worse overall performance. The wear of the self-mated graphite pairs was less than that of the graphite/copper pairs. The effect of the polarity on the graphite/graphite material combinations was negligible, while in the graphite/copper combinations the direction of the electrical current was found to significantly affect the wear of the discs. The wear of the positive graphite disc was up to 30% lower than the negative graphite disc, while the wear of the positive copper disc was up to 8 times more than that of the negative copper disc. Differences in the boundary contact film were observed in the graphite/copper contacts depending on the surface polarity, meaning that sliding contacts with the current flowing from the graphite disc to the copper disc saw less wear than the contacts where the current flows from the copper disc to the graphite disc.

Diplomska naloga opisuje izdelavo naprave za merjenje porabe električnih naprav na principu tokovnega merilnega upora. Glede na osnovne specifikacije naprava omogoča merjenje efektivne vrednosti izmeničnega toka do 25 A in kratke tokovne špice do 60 A. Naprava meri tudi električno napetost in fazni kot ter s tem omogoča izračun moči. Za izdelavo naprave je bilo potrebno načrtati električno shemo, izdelati knjižnice za program Altium Designer, izrisati tiskano vezje v tem programu in napisati programsko kodo. Program, napisan v programskem jeziku C, je sposoben z danimi elementi vzorčiti meritve, izračunati želene podatke in jih prikazati uporabniku na prikazovalnik LCD. Ob primerjavi izdelka z referenčnim instrumentom naprava meri znotraj predvidene napake, ki je nižja od 1 %, razen pri najmanjših vrednostih toka, kjer je relativna napaka meritve večja zaradi omejene ločljivosti in napake ničelnih vrednosti. Diploma thesis describes development and construction of the device for measuring power of electric appliances using current measuring resistor - shunt. According to the device specifications it is capable of measuring effective AC current up to 25 A and short current spikes up to 60 A. It also measures voltage and phase shift to be able to calculate the power. For constructing the device electrical schematic had to be designed, libraries for Altium Designer had to be made and PCB was designed. Program code, written in programming language C, is capable of sampling measurements, calculating wanted data and displaying them to the user via LCD. With comparison to the reference instrument the device is measuring within expected error under 1 %, except at lowest values, where the resolution and offset affects the measurement.

Cilj magistrske naloge je bil najti način za kontrolo prekrmiljenja konvencionalnega hidravličnega potnega ventila, krmiljenega z elektromagnetnimi aktuatorji, na podlagi meritve električnega toka med vklopom in izklopom elektromagnetnega aktuatorja. V okviru naloge smo predstavili metodo, ki temelji na izračunu magnetnega pretoka iz izmerjenega električnega toka. Metodo smo eksperimentalno in numerično preverili. Na podlagi izbrane metode smo izdelali napravo za kontrolo prekrmiljenja ventila. Napravo smo testirali in ugotovili, da je primerna za uporabo pri serijskem testiranju konvencionalnih potnih ventilov. The aim of this master’s thesis was to find a suitable solution for the switching control of a solenoid-operated hydraulic directional control valve based on measurement of the electric current during excitation and de-excitation of the actuator. In this thesis we present a method based on the calculation of the magnetic flux from the measured electric current. The method was tested experimentally and numerically. Based on the proposed method, a device for switching control of the valve was built. The device was tested and found to be suitable for series testing of directional control valves.

This paper reports on the performance and tribological mechanisms in a newly developed design for an electrical sliding contact in terms of sliding velocity, normal force and electrical current during 24-h experiments. Copper discs were run against hard-carbon graphite, electrographite and polymer-bonded graphite. The average wear rates of the copper discs against the three graphite materials were reduced to 10−8 and 10−7 mm3/Nm, and the graphite discs to 10−6 mm3/Nm, which is for 1 and 1–2 orders of magnitude less, than copper slip-rings and carbon brushes in conventional systems, respectively. The coefficient of friction was 0.2–0.4, depending on the conditions, which is comparable to the values of conventional electrical sliding contact. Tribofilms are generated in almost all contacts, and crucially determine the contact performance. The polymer-bonded-graphite/Cu formed the most compliant tribofilms that unify and decrease the local contact pressures and temperatures, and have the largest surface coverage that reduces the wear and contact resistance, which in turn reduces the contact instabilities and so the friction.

Sliding electrical contacts are used in devices for the conduction of electrical power or the electrical signals between stationary and moving parts. The most widely used electrical-sliding system is still the conventional slip ring and brush assembly. In the last decade, the lifetime of ring-brush contacts was extended through the use of better contact-material combinations and design improvements. However, the extremely rapid electrification of many more components has put severe demands on this extended lifetime. This paper presents a novel, patented design for two sliding discs that allows the use of advantageous graphite/graphite contacts. In the literature there is a serious lack of understanding the performance of sliding electrical contacts with graphite/graphite pairs, which depends on the key contact parameters, as well as the influence and potential of the different available graphite materials. The normal load, the contact velocity, the electric current, and the three self-mated graphite contacts, i.e., hard carbon, electrographite and polymer-bonded graphite, were investigated. The results indicate that the contact conditions influence the performance, which is also very dependent on the graphite materials. The polymer-bonded graphite showed the best results in this study.

Doktorsko delo obravnava vpliv obratovalnih parametrov (drsna hitrost, normalna kontaktna sila, električni tok in smer toka) na tribološke in električne lastnosti inovativne konstrukcije drsnega električnega kontakta. Namensko tribološko preizkuševališče, ki je tudi predstavljeno v tem delu, je bilo razvito v ta namen. Iz prvotnih osmih grafitnih materialov smo pri zahtevnejših obratovalnih pogojih izbrali tri grafitne materiale (trdi ogljik, elektrografit in polimerno vezan grafit) in jih nadalje podrobneje preučevali v isto-parnih kontaktih in v parih z bakrom. Pri vseh pogojih smo zaznali nastanek specifičnih površinskih filmov, ki ključno vplivajo na lastnosti drsnega električnega kontakta. Gladek, kompakten film, ki prekriva večino kontakta praviloma omogoča dobre tribološke lastnosti in stabilno obratovanje kontakta. Z grafit/grafit pari je možno doseči boljše tribološke in električne lastnosti kot z grafit/baker pari. Izbrani polimerno vezan grafit se je izkazal za najprimernejšega tako v paru z bakrom, še posebej pa v isto-parnem kontaktu. Smer električnega toka nima vpliva na obnašanje grafit/grafit kombinacij medtem, ko se pri grafit/baker kombinacijah negativne grafitne površine bolj obrabljajo od pozitivnih grafitnih ter pozitivne bakrene površine bolj od negativnih bakrenih površin. Rezultati dokazujejo velik potencial grafit/grafit materialnih kombinacij v disk-disk drsnem električnem kontaktu, saj je možno doseči dobro učinkovitost kontakta in zelo nizko obrabo. In the PhD thesis we have studied the influence of operating parameters (sliding velocity, normal contact force, electrical current and direction of the current) on the tribological and electrical properties of the innovative design of sliding electrical contact. A dedicated tribological test rig was developed for this purpose, and is also presented in this thesis. Out of the initial eight graphite materials, three graphite materials (hard carbon, electrographite and polymer-bonded graphite) were selected under the demanding operating conditions and were further tested and studied in detail. They were running against self-mated contacts and against copper. In all conditions, a specific surface film formation was detected, which have a key effect on the properties of the sliding electrical contact. Smooth, well-compacted film, that overlaps most of the contact, usually gives good tribological properties and stable contact operation. With graphite/graphite combinations better tribological and electrical properties than with graphite/copper combinations can be achieved. The chosen polymer-bonded graphite has proved to be the most suitable, both in pair with copper, and especially in contact with itself. The direction of the electrical current has no influence on the behaviour of the graphite/graphite combinations. Meanwhile, in the case of the graphite/copper combinations, the negative graphite surfaces wear more than the positive graphite surfaces, and the positive copper surfaces wear more than the negative copper surfaces. The results demonstrate the great potential of graphite/graphite material combinations in the disc-disc sliding electrical contact, as it is possible to achieve a good efficiency of the contact and very low wear.

Diplomska naloga Predšolski otroci spoznavajo vire električne energije je sestavljena iz teoretičnega in empiričnega dela. V teoretičnem delu je povzeta kognitivna razvojna teorija Jeana Piageta in raziskava otroških predstav o električnem toku Davida Shipstona. Dodan je tudi kratek opis ključnih besed s katerimi so se otroci seznanili v raziskovalnem delu. Drugi del diplomske naloge je empirični. Z individualnimi intervjuji sem ugotavljala predstave, ki jih imajo pet do šest let stari otroci o pojmih s področja elektrike in na ta način preverila svoje hipoteze o tem. Na osnovi analize odgovorov otrok na vprašanja med individualnimi intervjuji pred začetkom dejavnosti sem načrtovala dejavnosti, namenjene spoznavanju nekaterih pojmov s področja elektrike. Po izvedenih dejavnostih sem otrokom ponovno zastavila enaka vprašanja kot pred njimi. Analiza odgovorov otrok na vprašanja pred in po izvedenih aktivnostih nakazuje, da so se predstave otrok o pojmih, povezanih z električno energijo, dopolnile ali spremenile. V zaključku diplomske naloge je podan tudi predlog za nadaljne aktivnosti s področja raziskovanja električnega omrežja od vira do porabnika in električne napeljave od razdelilne omarice do končnega porabnika. The bachelor's degree titled Preschool Children Explore the Sources of Electrical Energy consists of theoretical and empirical part. The theoretical part is based on the theory of child cognitive development by Jean Piaget and on research on electric current perception of children by David Shipston. A short description of key words, introduced to the children in the research work, is added to the degree. The second part of the Bachelor's degree is empirical. During the research period hypotheses on electric current perception of 5- to 6-year-old children were proven. The research was based on children's response analysis of the investigative questions, received during individual interviews at the very beginning of the research. After the conclusion of the research, the children were tested again to check their gained knowledge on the electric current. The analysis of the questions before and after the research implies some changes in children's electric current perception, which was either improved or changed. In the conclusion of this degree there is a suggestion on how to continue the research on the electric power system from the source to its users and on electric installations from the junction box to the final consumer.

Uvod govori o pomembnosti merjenja električnega toka, opisane pa so tudi najpogostejše vrste merilnih pretvornikov. V nadaljevanju so predstavljeni različni principi merjenja ter z njimi povezani različni tokovni merilni pretvorniki. Na osebnem računalniku v okolju Agilent VEE Pro smo izdelali objektni program za nastavitev laboratorijskih instrumentov za merjenje. Zgradili smo vezave različnih tokovnih merilnih pretvornikov. Z vzorčenjem dveh digitalnih multimetrov smo zajeli vrednosti, s pomočjo vrednosti pa izdelali grafe (karakteristike). Z njimi smo ponazorili pogreške različnih tokovnih merilnih pretvornikov v odvisnosti od različnih velikosti in različnih frekvenc električnega toka. Introduction discusses the importance of measuring the electric current, as well as describing the most common types of measurement transducers. The following are the different principles of measurement and related different current measuring transducers. On the PC environment, using Agilent VEE Pro we made object setup of laboratory instruments used for measuring. We have built a circuit with different current measuring transducers. By sampling two digital multimeters values have been captured and from them according graphs (characteristics) were produced. Using these graphs we illustrated errors of different current measurement converters, depending on the different amplitudes and different frequencies of electric current.

V diplomskem delu so predstavljene osnove nadzemnih daljnovodov in opisani vsi potrebni koraki za modeliranje daljnovoda v programu Abaqus CAE. Osredotočil sem se na izdelavo daljnovoda, pri čemer sem opisal vsak korak modeliranja. Daljnovod je sestavljen iz stebra, vodnika in plošče, na katerem stoji steber. Na zmodeliranem daljnovodu je še določena mreža vsakega dela konstrukcije, material, robni pogoji in obremenitve žledu ter vetra. Kot rezultat danih obremenitev dobimo napetosti in pomike, ki vplivajo na zmodeliran daljnovod. Opisani so tudi rezultati, vplivni parametri in možnosti za optimiziranje. This thesis explains the functioning of overhead power lines and describes the steps of power line modeling with the Abaqus CAE program. Focusing on overhead power line modeling, I described all the steps in detail. The overhead power line consists of a conductor, a panel, and a utility pole, which is located on the panel. When modelling a power line, the finished product includes a mesh of every part of the model, the material, the boundary conditions and the load of sleet and wind. The results of the loads are tensions and displacements, which influence the overhead power line. The thesis also includes the results, influential parameters and possibilities for optimization.