Magnetic Forces and Vibration in Wind Power Generators: Analysis of Fractional-Slot Low-Speed PM Machines with Concentrated Windings
Doctoral thesis
Permanent lenke
http://hdl.handle.net/11250/2360326Utgivelsesdato
2015Metadata
Vis full innførselSamlinger
- Institutt for elkraftteknikk [2429]
Sammendrag
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 machines is a direct-drive energy conversion
system for wind turbines. Due to the presence of the low spatial harmonic orders in the
radial forces distribution, fractional slot machines with concentrated windings can
potentially have a higher vibration level than the traditional PM machines.
In order to investigate the magnetic vibration characteristics, flux density distribution is
computed using finite element (FE) analysis. Then, the radial and tangential force densities
are calculated using the Maxwell stress tensor. Spatial harmonic analysis of the radial force
density distribution provides important information regarding the vibration behavior of the
machine. The radial force distribution on the stator teeth are calculated and employed as
input to a structural FE analysis. In this analysis, deformations in the stator bore due to the
exciting magnetic forces are computed. Experimental work is performed on a prototype
120-slot/116-pole PM generator to validate the magnetic and structural simulations.
The influence of pole and slot combinations is investigated by comparing PM machines
with 120 slots and 80, 112, 116 and 118 poles. Radial forces and vibration, the cogging
torque and the torque ripple characteristics of these machines are studied. The effects of the
slot harmonic are investigated in the prototype machine. It is discussed how the vibration
behavior is changed in the case of different slot closures. The influence of loading is
studied systematically; it is discussed how the d-axis and q-axis currents change the
amplitude of the lowest spatial harmonic of the radial forces, and consequently the
vibration level of the prototype machine.
Består av
Paper 1: Valavi, Mostafa; Nysveen, Arne; Nilssen, Robert; Lorenz, Robert D.; Rølvåg, Terje. Influence of pole and slot combinations on magnetic forces and vibration in low-speed PM wind generators. IEEE transactions on magnetics 2014 ;Volum 50.(5) is not included due to copyright available at http://dx.doi.org/10.1109/TMAG.2013.2293124Paper 2: Valavi, Mostafa; Nysveen, Arne; Nilssen, Robert; Rølvåg, Terje. Slot harmonic effect on magnetic forces and vibration in low-speed permanent-magnet machine with concentrated windings. IEEE transactions on industry applications 2014 ;Volum 50.(5) is not included due to copyright available at http://dx.doi.org/10.1109/TIA.2014.2309717
Paper 3: Valavi, Mostafa; Nysveen, Arne; Nilssen, Robert. Effects of Loading and slot harmonic on Radial Magnetic Forces in Low-Speed Permanent Magnet Machine with Concentrated Windings. IEEE transactions on magnetics 2015 ;Volum 51.(6) is not included due to copyright available at http://dx.doi.org/10.1109/TMAG.2014.2377014