Blar i Institutt for elkraftteknikk på forfatter "Valavi, Mostafa"
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Analyse av magnetfelt og tap ved enderegionen i direkte vannkjølte generatorer
Lid, Arne Moen (Master thesis, 2018)Denne masteroppgaven er en fortsettelse av prosjektoppgaven som ble utført høstsemesteret 2017. I den oppgaven ble det modellert en 2D- og 3D-modell i ANSYS Electronics basert på en av Statkraft AS sine store synkrongeneratorer. ... -
Analysis of Additional Eddy-Current Copper Losses in Large Converter-Fed Hydropower Generators
Engevik, Erlend Løklingholm; Valavi, Mostafa; Nysveen, Arne (Chapter, 2018)This paper investigates the effect of converter operation on AC copper losses in the stator and damper windings of a large hydrogenerator. Stator currents are computed using finite element simulations. The computed current ... -
Analysis of magnetic forces and vibration in a converter-fed synchronous hydrogenerator
Valavi, Mostafa; Nysveen, Arne; Nilsen, Roy; Le Besnerais, Jean; Devillers, Emile (Chapter, 2017)This paper investigates the influence of converter-fed operation on magnetic forces and radial vibration in a hydrogenerator. Flux density distribution is computed using time-stepping finite element (FE) analysis and used ... -
Effects of lifting reactance requirements on the optimal design of converter-fed synchronous hydrogenerators
Engevik, Erlend L.; Nysveen, Arne; Valavi, Mostafa; Hestengen, Truls (Chapter; Peer reviewed, 2017)The maximum allowed per unit value of the synchronous reactance of a synchronous generator is normally decided by the grid codes in order to maintain the stability of the system. For the converter-fed synchronous hydrogenerator, ... -
Electromagnetic analysis and electrical signature-based detection of rotor inter-turn faults in salient-pole synchronous machine
Valavi, Mostafa; Jørstad, Kari Gjerde; Nysveen, Arne (Journal article; Peer reviewed, 2018)In this paper, rotor inter-turn faults in salient-pole synchronous machines are investigated using finite-element analysis. The machine under study is a 22 MVA eight-pole hydropower generator with fractional-slot windings. ... -
Influence of Converter Topology and Carrier Frequency on Airgap Field Harmonics, Magnetic Forces, and Vibrations in Converter-Fed Hydropower Generator
Valavi, Mostafa; Devillers, Emile; Le Besnerais, Jean; Nysveen, Arne; Nilsen, Roy (Journal article; Peer reviewed, 2018)This paper investigates the effects of converter-fed operation on magnetic forces and vibration in a hydrogenerator. The variable-speed hydrogenerator (in a pumped-storage power plant) is a large synchronous machine with ... -
Influence of winding layout and airgap length on radial forces in large synchronous hydrogenerators
Engevik, Erlend L.; Valavi, Mostafa; Nysveen, Arne (Chapter, 2017)This paper investigates the flux density and radial force spatial harmonics in large salient pole synchronous hydro-generators. Vibration due to magnetic forces are mainly caused by low order harmonics in the airgap flux ... -
Investigation of magnetic field and radial force harmonics in a hydrogenerator connected to a three-level NPC converter
Valavi, Mostafa; Nysveen, Arne; Nilsen, Roy (Chapter, 2017)This paper investigates spatial and time harmonics of flux density and radial force distributions in the airgap of a hydrogenerator with fractional-slot windings. Hydrogenerator is connected to a neutral-point-clamped (NPC) ... -
Magnetic Forces and Vibration in Wind Power Generators: Analysis of Fractional-Slot Low-Speed PM Machines with Concentrated Windings
Valavi, Mostafa (Doctoral thesis at NTNU;2015:204, Doctoral thesis, 2015)The PhD research work presented in this thesis deals with radial magnetics forces and vibration in low-speed fractional-slot permanent magnet (PM) machines with concentrated windings. One of the applications of such ... -
Modelling, Simulation, and On-line Detection of Rotor Eccentricity in Hydropower Generators
Møller, Andreas Blix (Master thesis, 2018)The generator is a critical component in the hydropower power plant, and detection of its fault conditions is important for safe and cost-effective operation. A new proposed method for detection of rotor interturn short ... -
Variable-speed operation of hydropower plants: past, present, and future
Valavi, Mostafa; Nysveen, Arne (Journal article; Peer reviewed, 2018)In This article, the state of the art in the variable-speed operation of hydropower plants is reviewed, with a focus on pumped-storage hydropower. Relevant literature is reviewed to address the benefits of variable-speed ... -
Vibrations from Magnetic Forces in Hydropower Generators
Pascal, Jules (Master thesis, 2016)Electrical machines using a fractional slot winding can be subject to low modes of vibration, which can produce noise and stator deformation. The design of a machine has an influence on the amplitude of these deformations, ...