| 11. |
|
|
| 12. |
|
|
| 13. |
|
|
| 14. |
- Danielsson, Oskar, et al.
(författare)
-
Flux Distribution in Linear Permanent-Magnet Synchronous Machines Including Longitudinal End Effects
- 2007
-
Ingår i: IEEE transactions on magnetics. - 0018-9464 .- 1941-0069. ; 43:7, s. 3197-3201
-
Tidskriftsartikel (refereegranskat)abstract
- We investigated the longitudinal ends' influence on the flux distribution in a permanent-magnet linear synchronous machine with an analytic model and with numeric finite-element methods. We derived a general analytic expression, on closed form, from a linear reluctance model. The model reveals that the flux in a linear machine differs from that in a rotating machine in several aspects. The longitudinal ends introduce a pairwise coupled flux pattern, which will behave differently in circuits with odd or even numbers of magnets. In linear machines with an even number of magnets the pairwise coupled flux will spread throughout the whole machine, whereas in linear machines with an odd number of magnets it will be transformed into an equally distributed flux in the middle. The latter case will give rise to a nonsymmetric air gap flux distribution, where every second pole has larger flux. We confirmed the pairwise coupled flux and the nonsymmetric air gap distribution predicted by the analytic model by finite-element simulations. We noted additional effects when nonlinear behavior of the steel is taken into account. We conclude that saturation counteracts the pairwise coupled flux pattern at the longitudinal ends. Again, a nonsymmetric air gap flux distribution occurs as the pairwise coupled flux is transformed into an equally coupled flux. The pairwise coupling of the flux and the nonsymmetric air gap flux distribution give rise to a number of secondary effects, which we discuss.
|
|
| 15. |
- Danielsson, Oskar, et al.
(författare)
-
Study of a Longitudinal Flux Permanent Magnet Linear Generator for Wave Energy Converters
- 2006
-
Ingår i: International Journal of Energy Research. - : Hindawi Limited. - 0363-907X .- 1099-114X. ; 30:14, s. 1130-1145
-
Tidskriftsartikel (refereegranskat)abstract
- A directly coupled linear permanent magnet generator of longitudinal flux-type is investigated. The generator will be used for power take-off in a wave energy converter. A combined field- and circuit model, solved by a time stepping finite element technique, is used to model and analyse the electromagnetic behaviour of the machine. A large number of simulations form the basis of a design study where the influence of armature current level, number of cables per slot, and pole width is investigated with respect to efficiency, generator size, and the load angle. A case study is performed for a chosen generator design. The electromagnetic behaviour is examined both for nominal load and for overloads. The generator has a nominal output power of 10 kW for a constant piston speed of 0.7 m s(-1). The electromagnetic efficiency at nominal load is 86.0%, the load angle 6.6 degrees, and the power fluctuation 1.3%. At 300% overload the load angle barely exceeds 12 degrees and the cable temperature is below 25 degrees C provided that the stator back is thermally connected to the sea water. The numerical calculations have been verified for small speeds by experiments.
|
|
| 16. |
- Danielsson, Oskar, 1975-
(författare)
-
Wave Energy Conversion : Linear Synchronous Permanent Magnet Generator
- 2006
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis studies the electric aspects of a linear synchronous permanent magnet generator. The generator is designed for use in a wave energy converter, which determines the fundamental requirements of the generator. The electromagnetic properties of the generator are investigated with a finite element based simulation tool. These simulations formed the base of the design and construction of a laboratory prototype. Several experiments where conducted on the prototype generator. The results verify at large the simulation tool. However, a difference between the measured and simulated air gap flux was discovered. This was attributed to the longitudinal ends of the generator, which are ignored in the simulation tool. Experiences from the construction, and further finite element studies, led to a significant change in the support structure of the first offshore prototype generator. A complete wave energy converter was constructed and launched, the 13th of March, on the west coast of Sweden. A study of the load resistance impact on the power absorption has been carried out. An optimal load interval, with regard to power absorption, has been identified. Furthermore, the generator has proofed to withstand short term overload several times larger than the nominal load. Finally, the longitudinal ends’ influence on the flux distribution was investigated with an analytical model, as well as finite element simulations. A possible problem with large induction of eddy currents in the actuator back steel was identified.This work is a part of a larger project, which aims do develop a viable wave energy conversion system.
|
|
| 17. |
- Deglaire, Paul, et al.
(författare)
-
Conformal mapping and efficient boundary element method without, boundary elements for fast vortex particle simulations
- 2008
-
Ingår i: European journal of mechanics. B, Fluids. - : Elsevier BV. - 0997-7546 .- 1873-7390. ; 27:2, s. 150-176
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, a revitalization of conformal mapping methods applied to fluid flows in two dimensions is proposed. The present work addresses several important issues concerning their application for vortex particle flow solvers. Difficulties of past conformal based method are reviewed. One difficulty concerns the ability of a mapping procedure to represent complicated shapes. The present paper improves past algorithms to be able to map new shapes, including multiply connected domains. A new fast procedure allows transferring a set of points in the mapped simplified plane to the complicated domain and vice versa. After a mapping construction, it is demonstrated how basic exact solutions to potential flow problems with vortices can be put in a new form which provides a faster and more accurate computation than with distributed singularity methods.
|
|
| 18. |
|
|
| 19. |
- Engström, Jens, et al.
(författare)
-
Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body
- 2009
-
Ingår i: Journal of Applied Physics. - USA : American Institute of Physics. - 0021-8979 .- 1089-7550. ; 106:6
-
Tidskriftsartikel (refereegranskat)abstract
- The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units.
|
|
| 20. |
|
|
