<p>Harmonics are a well-known problem that has to be dealt with in the design of thegenerator. Internationally accepted standards limits the amount of harmonics allowedin the no-load voltage. These limits can be difficult to fulfill with integral slot winding,where the number of slots per pole and phase is an integer. The presence of thedamper winding often makes the problem with harmonics even worse and harmonicswith frequencies of order 6q±1 arise with significant amplitude. How the damperwinding is designed affect the content of harmonics in the no-load voltage and the aimwith these … has been to investigate in which extent design of the damper windingaffects the contents of harmonics.Simulations with the 2-D finite element method have showed that if the damper barsis centered in the pole shoe, the amplitude of the harmonics of order 6q±1dependsboth on the ratio between the stator slot pitch and damper bars slot pitch and if thedamper bars are connected between the poles or not.If the damper bars is displaced with ¼ stator slot pitch alternately, the amplitude ofthe harmonics of order 6q±1 is reduced and the influence of the ratio between thestator slot pitch and the damper bars slot pitch will vanish. To minimize the loss inthe damper bars the distance between the damper bars should then be equal thedistance between the stator slots.</p>

Harmonics are a well-known problem that has to be dealt with in the design of thegenerator. Internationally accepted standards limits the amount of harmonics allowedin the no-load voltage. These limits can be difficult to fulfill with integral slot winding,where the number of slots per pole and phase is an integer. The presence of thedamper winding often makes the problem with harmonics even worse and harmonicswith frequencies of order 6q±1 arise with significant amplitude. How the damperwinding is designed affect the content of harmonics in the no-load voltage and the aimwith these … has been to investigate in which extent design of the damper windingaffects the contents of harmonics.Simulations with the 2-D finite element method have showed that if the damper barsis centered in the pole shoe, the amplitude of the harmonics of order 6q±1dependsboth on the ratio between the stator slot pitch and damper bars slot pitch and if thedamper bars are connected between the poles or not.If the damper bars is displaced with ¼ stator slot pitch alternately, the amplitude ofthe harmonics of order 6q±1 is reduced and the influence of the ratio between thestator slot pitch and the damper bars slot pitch will vanish. To minimize the loss inthe damper bars the distance between the damper bars should then be equal thedistance between the stator slots.

På senare år har efterfrågan på stålmaterial av låg vikt ökat, speciellt inom transportsektorn. Genom att addera Al till stål sänks densiteten vilket gör att FeAl-legeringar är ett lovande material för fordonskonstruktion. Vätskekorrosionsegenskaper undersöktes av 3D – printade FeAl prover som innehöll 0 – 10 vikt% Al och 0,1 vikt% Zr för att bestämma hur korrosionsegenskaperna förändrades med avseende på Al – innehållet. Korrosionsresistansen var i stor utsträckning beroende av huruvida en passiv film av Al2O3 bildades på ytan eller ej. Korrosionshastigheten bestämdes genom EIS – och PDP – analyser utförda i 3,5 vikt% NaCl-lösning samt genom viktförlusttester i 1 M HCl respektive 0,5 M H2SO4. Vidare karaktäriserades proverna genom XRF, XRD, EDS, SEM och optisk mikroskopi vilket bland annat visade på att samtliga prover var enfassystem samt att den kemiska sammansättningen var enligt förväntan. Vidare indikerade optisk mikroskopi och SEM att ett högre Al – innehåll resulterar i att proverna blir mer porösa. Elektrokemiska tester antyder att ett Al – innehåll om 10 vikt% förbättrade korrosionsresistansen. Detta antyder möjligen, men kan inte definitivt fastslås från de utförda experimenten, att det krävs 10 vikt% Al för att en passiv film som täcker hela materialytan ska bildas. Korrosionshastigheten var 7 – 10 gånger högre vid viktförlusttest jämfört med elektrokemiska test. Detta förklaras genom att den skyddande passiva filmen bröts ned under de sura förhållanden som viktförlusttesten utfördes i medan den passiva Al2O3 filmen kunde bestå i de pH – neutrala förhållanden som elektrokemiska test utfördes vid. Detta speglar att bildandet och stabiliteten av Al2O3-filmen är vitalt för att sänka korrosionshastigheten. / In recent years the demand for lightweight ferritic steels has increased, particularly for transport applications. The addition of Al lowers the density, hence making FeAl alloys promising materials for such constructions. Aqueous corrosion properties of 3D – printed FeAl samples ranging from 0 – 10 wt% Al and containing 0.1 wt% Zr were investigated to determine how the Al content affects the corrosion resistance. The corrosion rate was found to greatly depend on the formation and stability of a protective passive film of Al2O3 forming on the material surface. A corrosion rate was obtained via EIS and PDP in 3.5 wt% NaCl as well as via weight loss testing in 1 M HCl and 0.5 M H2SO4. Additionally, XRF, XRD, EDS, SEM and optical microscopy tests were carried out to characterize the samples. XRF and EDS confirmed that the elemental composition of the samples was as expected and XRD indicated that all samples were single phase systems. Furthermore, optical microscopy and SEM indicated that higher Al content makes the samples more porous. Electrochemical testing indicated that addition of 10 wt% Al greatly improves the corrosion properties suggesting that it may require 10 wt% Al to form a passive film that covers the whole surface, although this cannot be said for certain from these experiments. Moreover, the corrosion rate was 7 – 70 times lower during electrochemical testing compared to weight loss testing, in which the passive film breaks down due to the acidic conditions. This emphasizes that the stability of the Al2O3 film is vital for slowing down the corrosion rate of FeAl alloys.

Organic solar cells (OSCs) based on non-fullerene acceptors (NFAs) have attracted a great deal of attention in recent years due to their rapidly increasing efficiency and enormous potential. In this work, the optical and electronic properties of systems containing the very promising non-fullerene acceptor PYT have been thoroughly studied with the use of the density functional theory (DFT) and the time-dependent density functional theory (TDDFT). By changing the electron linker from thiophene to furan and selenophene, respectively, the PYT was divided into three variants, each of which was studied independently. In addition, these three systems were combined with the donor PBDB-T to generate two distinct interface conformations. The properties studied in this work include the optimized geometries, HOMO-LUMO levels, UV-Vis spectra, frontier molecular orbitals (FMOs), natural transition orbitals (NTOs), density of states (DOS), dipole moments, open-circuit voltages, exciton binding energies, and local exciton (LE) and charge transfer (CT) energies. The calculations were performed in chlorobenzene solution utilizing the polarizable continuum model (PCM). It was discovered that PBDB-T/PY-Se exhibited remarkable flatness employing the π-π stacking conformation which corresponds well with the excellent D/A compatibility observed experimentally. All interfaces displayed appropriate positioning of the HOMO-LUMO levels, with the acceptor dominating the LUMO and the donor dominating the HOMO, with HOMO-LUMO gaps ranging between 1.34 and 1.38 eV. The differences in the interchanging of the electron linker were not that significant, and neither was the change in interface conformation in terms of the HOMO-LUMO levels. This may indicate that the system can be effective even without the presence of a π-π stacking conformation. The first excited states for all interface systems were shown to be pure CT transitions, and on average, 80% of the states exhibit CT character. The remaining contributions consisted of transitions within the pure materials, with a larger contribution within the acceptor. The theoretical results of this study indicate that systems containing the novel polymer acceptor PYT and its variants PY-O and PY-Se exhibit very intriguing properties, and further development of OSCs containing these polymers might further aid in the development of high-performance OSCs. / Organiska solceller (OSC) baserade på icke-fullerenacceptorer (NFA) har väckt stor uppmärksamhet de senaste åren på grund av dess snabbt ökande effektivitet och enorma potential. I detta arbete har de optiska och elektroniska egenskaperna hos system innehållande den mycket lovande icke-fullerenacceptorn PYT studerats grundligt med användning av täthetsfunktionalteorin (DFT) och den tidsberoende täthetsfunktionalteorin (TDDFT). Genom att ändra elektronförbindelsen från tiofen till furan respektive selenofen så delades PYT upp i tre varianter som var och en studerades oberoende av varandra. Dessutom kombinerades dessa tre system med donatorn PBDB-T för att generera två distinkta gränssnittskonformationer. Egenskaperna som studeras i detta arbete inkluderar optimerade geometrier, HOMO-LUMO-nivåer, UV-vis spektra, gränsmolekylära orbitaler (FMO), naturliga övergångsorbitaler (NTO), tillståndstäthet (DOS), dipolmoment, tomgångsspänning, excitonbindningsenergi samt lokal exciton (LE) och laddningsöverförings (CT) energier. Beräkningarna utfördes i klorbensenlösning med användning av den polariserbara kontinuummodellen (PCM). I resultatet uppvisade PBDB-T/PY-Se en anmärkningsvärd planhet med användning av π-π staplingskonformationen som överensstämmer väl med den utmärkta D/A-kompatibiliteten som observerats experimentellt. Alla gränssnitt visade lämplig positionering av HOMO-LUMO-nivåerna, med acceptorn som dominerade LUMO och donatorn som dominerade HOMO, med HOMO-LUMO-gap mellan 1.34 och 1.38 eV. Skillnaderna i utbytet av elektronförbindelsen visade sig inte vara signifikanta och inte heller skillnaden i gränssnittskonformation när det gäller HOMO-LUMO-nivåerna. Detta kan indikera att systemet kan vara effektivt även utan förekomst av π-π staplingskonformation. De första exciterade tillstånden för alla gränssnittssystem visade sig vara rena CT-övergångar och i genomsnitt uppvisade 80% av tillstånden CT-karaktär. Resterande andel bestod av övergångar inom de rena materialen med en större andel inom acceptorn. De teoretiska resultaten av denna studie indikerar att system innehållande den nya polymeracceptorn PYT och dess varianter PY-O och PY-Se uppvisar mycket spännande egenskaper samt att vidareutveckling av OSC:er som innehåller dessa polymerer ytterligare kan hjälpa till i utvecklingen av högpresterande OSC:er.