The main objective of this thesis is study the overall performance of extremely low speed direct drive permanent magnet generators for energy conversion from marine and tidal currents. Different factors involved with the modelling of these generators as well as their electro-magnetic modelling making use of the finite element simulations are provided. To do a detailed researh, a 5 kW model generator was built in accordance with finite element based simulations. A number of tests had been performed on the model generator. The experimental outcome was weighed against the corresponding case simulations on the developed generator. The variations between the end result is forecasted by the simulations and those predicted by the measurements had been under 10%. We have investigated the part and overload performance of the generator and it is found from both simulations and measurements that the generator is in the position to efficiently operate at different speeds. The tests on the experimental generator were done for speeds ranging between 2 and 16 rpm as well as for load variations of 0.5 to 2 per unit. Throughout this dissertation it is shown that it is feasible to develop a very low speed direct drive generator for virtually any marine current site which is good for projects planning to create a technical and economical viable marine current energy conversion system.
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Contents
Introduction
Marine Current Energy
The Marine Current Energy Conversion System Studied in this Thesis
Vertical Axis Turbines
Direct Drive Permanent Magnet Generators
Outline of the Thesis
Resource and Technology
Marine Currents
Tidal Currents
Ocean Currents
Other Currents
Potential for Energy Extraction
Technology Assessment
Different Approaches for Marine Current Energy Conversion
Prototypes
Generator Theory and Modelling
Generator Theory in General
Power Angle
Permanent Magnet Excitation Systems
Armature Winding
Generator Losses and Efficiency
Detailed Generator Modelling
Finite Element Modelling
Boundary Conditions
Permanent Magnet Modelling
Thermal Modelling
Simulation Procedure
Electromagnetic Forces in PM Generators
Numerical Methods to Calculate EM Forces
Magnetic Circuit Approach for Modelling the Magnetic Forces
Design of the Experimental Generator
Design Considerations
Armature Winding
Stator Dimensions
Rotor Design
Summary of the Machine Design Parameters for Construction
The Experimental Setup
Generator Performance Analysis
Experiments: Analysis and Results
Preparatory Measurements
No Load Analysis
Load Analysis
Conclusions………
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Source: Uppsala University Library