In this thesis permanent magnet **direct drive generator for power conversion from water currents** is studied. Water currents as a power source involves a number of constrains as well as possibilities, especially when direct drive and permanent magnets are considered. The high power fluxes and low current velocities of a water current, in combination with its natural variations, will affect the way the generator is operated and, flowingly, the appearance of the generator. The work in this thesis can, thus, be categorized into two general topics, generator technology and optimization. Under the first topic, fundamental generator technology is used to increase the efficiency of a water current generator. Under the latter topic, water current generators are optimized to a specific environment. The conclusion drawn from this work is that it is possible to design very low speed direct drive generators with good electromagnetic properties and wide efficiency peak.

*Contents*

Acknowledgments

Introduction

The Resource

Tidal currents

Constant currents

Power Conversion

Design and simulation of electric machines

Method

Mathematical model of a generator

Geometry

Analysis

Summary of Papers

Generator Technology

Paper A: E. Segergren, B. Bolund, H. Bernhoff and M. Leijon, Rotor

Concept Comparison for Underwater Power Generation

Paper B: E. Segergren, K. Nilsson and M. Leijon, Frequency Optimisation With Respect to Weight and Electric Efficiency for

Direct Drive Underwater Power Generator

Paper C: E. Segergren and Mats Leijon, Relation Between Generator Geometry and Resistance in Armature Winding

Paper D: K. Nilsson, E. Segergren, and M. Leijon, Analysis of Low

Speed Permanent Magnetized Generators for use in Marine Current

Speed Permanent Magnetized Generators for use in Marine Current

Power Conversion Optimization

Paper E: K. Nilsson, E. Segergren, and M. Leijon, Simulation of Direct Drive Generators Designed for Underwater Vertical Axis

Turbines Paper F: E. Segergren, K. Nilsson, E. Sjöstedt, J. Sundberg and M.

Leijon, Converting Kinetic Energy in Water Currents Using Direct Drive Generators

Paper G: E. Segergren, K. Nilsson, D.P. Coiro and M. Leijon, Design

of a Very Low Speed PM Generator for the Patented KOBOLD Tidal Current Turbine

Paper H: B. Bolund, K. Thorburn, E. Sjöstedt, M. Eriksson, E.

Segergren and M. Leijon, Upgrading Generators with New Tools and

High Voltage Technology

Paper I: E. Segergren, K. Nilsson and M. Leijon, Permanent

Magnetized Generator for Marine Current Power Conversion – Proposed Experimental Setup

Paper J: Assembly comprising a Water Turbine and a Generator, the

Rotor of which is Direct-Connected to each one of the Blades the Turbine

Summary of Results and Discussion

Generator Technology

Optimization

Conclusions

Suggestions for Future Work

References

Author: Segergren, Erik

Source: Uppsala University Library

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