Browsing NTNU Open by Author "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. ... -
Fault Detection and Diagnosis of Induction Motor for Ship Propulsion by utilizing Electrical Signature and Finite Element Method
Breivik, Andreas (Master thesis, 2021)Induksjonsmotoren studert i denne masteroppgaven er en av to fremdriftsmotorer installert ombord polarforsynings- og forskningsfartøyet SA Agulhaus II og arbeidet er et bidrag til HealthProp-prosjektet (HealthProp 2020). ... -
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 ... -
On Uncertainty Assessment of Fatigue Damage of Propulsion Shaft Under Ice Impact
Purcell, Etienne; Nejad, Amir R.; Valavi, Mostafa; Bekker, Anriëtte (Chapter, 2021)In this paper, the importance of maintenance of marine propulsion is discussed with specific focus on the use of condition monitoring to inform maintenance schedules. The design requirements of DNV GL for shafts expected ... -
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, ...