Main target of the PERMAGWIT project was the design, manufacturing and testing of an extremely silent, efficient and reliable 1.5MW direct drive generator system for gearless pitch-controlled wind turbines. A prototype of the generator, the electronic power converter and a suitable turbine nacelle should be developed within this project.
The design phase of the generator has been completed successfully:
- Diameter, length and weight are important aspects for transport and erection of the turbine. The generators outer diameter is not bigger than 3.8 m to allow to pass most bridges and tunnels, leading to decreased transportation cost.
- Using an outer rotor concept significantly reduces length and thus weight of the generator because of increased air gap diameter. Furthermore the magnets can easily be cooled naturally by the surrounding wind.
- The generator housing will be a fully-enclosed design in order to prevent insulation problems of the stator winding and corrosion of the permanent magnets. Additionally, noise reduction can be achieved.
- An optimum pole geometry has been elaborated reducing the overall inductance of the generator and thus decreasing the load angle and increasing the power factor.
- A Neodymium-Iron-Boron magnet material was chosen from the state-of-the-art rare earth magnet materials with improved magnetic properties and high chemical stability important for long time reliability.
- Using 690V technology has the advantage of a modular assembly of the converter simplifying manufacturing and maintenance. The generator is not negatively affected and standard components can be used.
- The internal generator voltage (EMF) has been chosen to 570V with contribution to the safety margin occurring at a maximum of 22% over speed.
- Round wire has been chosen due to simplified manufacturing and cost reduction.
- Advantages of water-cooling are that a fully encapsulated generator design can be achieved leading to good corrosion protection. Furthermore it is possible to increase the maximum current in the generator and thus decrease the size of the generator.
- Wind energy production is enlarged due to significantly increased partial load efficiency based on the use of permanent magnets and the omission of a gearbox.
- Weight and cost of the generator active part is reduced due to high utilisation based on detailed optimisations.
- Avoiding the gearbox and applying an advanced rectifier control concept together with low rotor speed will lead to a distinctive decrease of the present noise level at low wind speeds.
- Wind energy production is enlarged due to significantly increased partial load efficiency based on the use of permanent magnets and the omission of a gearbox in combination with thorough optimisations.
Manufacturing of the generator has not been finished due to the missing bearing. However, all parts are in stock at ELINs facilities and ready for use. The converter has not been manufactured, too. Due to the fact that the manufacturing is not finished the major testing could unfortunately not start.