This thesis aims to simulate and find out more about the electrical dynamics of a six-phase exciter for hydropower generators. Because ordinary electric circuit-based simulation software only simulate three-phase electrical systems, a FEM-based software is used for the electrical dynamics simulations of the six-phase system. The objective is to analyse the pulsation behaviour of the rectified electrical output on the six-phase system and compare it to the three-phase system. The three-phase system is also simulated with filters with the aim of decreasing the amplitude of the pulsations on the electrical output. It is expected that an upgraded system from a three-phase system to a six-phase system should double the pulsation frequency on the rectified electrical output. However, the result shows that the rectified electrical output of the six-phase system consists of pulsations with unexpected frequencies. The simulated RL-filter on the three-phase system shows only insignificantly small changes on the rectified electrical pulsation amplitude.

This thesis aims to simulate and find out more about the electrical dynamics of asix-phase exciter for hydropower generators. Because ordinary electric circuit-basedsimulation software only simulate three-phase electrical systems, a FEM-basedsoftware is used for the electrical dynamics simulations of the six-phase system. Theobjective is to analyse the pulsation behaviour of the rectified electrical output on thesix-phase system and compare it to the three-phase system. The three-phase systemis also simulated with filters with the aim of decreasing the amplitude of the pulsationson the electrical output.It is expected that an upgraded system from a three-phase system to a six-phasesystem should double the pulsation frequency on the rectified electrical output.However, the result shows that the rectified electrical output of the six-phase systemconsists of pulsations with unexpected frequencies. The simulated RL-filter on thethree-phase system shows only insignificantly small changes on the rectified electricalpulsation amplitude.

This project aims to provide fish keepers with a safe and simple way to feed their pets while abroad or in any other situation where they do not have the ability to feed their fish by hand. Overfeeding is an unfortunate albeit common reason for mass death in an otherwise safe and healthy aquarium. While overfeeding to land dwelling pets might have negative health implications, the rapid damage seen in an aquarium is unparalleled in other environments. This is due to the release of ammonia that occurs when excess food (and partially fecal matter) is decomposed. Moderate feedings provide adequate nutrition for the pets, while keeping ammonia production at a level where it can be converted to nitrite and lastly the rather harmless compound nitrate. Most, if not all, feeders on the market today base their feedings solely off of volume, but this can lead to large variations in feeding size, due to variations in air between pellets in the feeding portions. By adding a failsafe with weight, we can fully prevent any chance of overfeeding, and thus ensuring a long and healthy life for our pets. Overall the goals of a safe fish feeder were accomplished, although the weighing was not as accurate as it optimally would have been. / Med det här projektet syftar vi på att tillförse akvarieägare med ett tryggt och enkelt sätt att mata sina fiskar när de är utomlands eller av annan anledning inte har möjlighet att mata för hand. Övermatning är en olycklig men dessvärre vanlig anledning till massdöd i ett annars hälsosamt akvarium. Även om övermatning hos landdjur kan ha ohälsosamma konsekvenser, så är det aldrig lika skadligt på kort sikt som det är i ett akvarium. Det här beror på att överbliven mat (och även till viss del avföring) i en vattenmiljö snabbt omvandlas till ammoniak under förmultning. Lagom stora matningar ger all näring fiskar behöver, medan enbart en halt ammoniak som kan omvandlas till nitrit och därefter det relativt harmlösa nitratet uppstår snabbt nog för att vara ofarligt. De flesta - om än inte alla - fiskmatare på marknaden idag baserar sina portioner på enbart volym. På grund av variationer i mängden luft mellan foder så kan då mängden mat ha stor variation. Genom att lägga till en säkring med vikt, så kan vi helt och hållet motverka all risk för övermatning, och på så vis säkerställa ett långt och hälsosamt liv för våra husdjur. Överlag lyckades vi skapa ensäker fiskmatare, men dessvärre var inte vågen lika noggrann som den optimalt hade varit.