Objective
To manufacture a 10 kW wind turbine utilising a directly coupled slow speed alternator on the turbine main shaft to produce a simple two bearing wind turbine generator capable of delivering alternating current at conventional voltage and frequency for use with readily available appliances. By mounting the wind turbine rotor and the alternator rotor on a common shaft the simplest possible mechanical arrangement is achieved, eliminating gearbox, couplings and auxiliary bearings with the attendant alignment, noise and maintenance problems. A safety brake disc would also be mounted on the common shaft for the dual purpose of control and emergency mechanical braking as a back up to electrodynamic braking through the control system. Control of the wind turbine would utilise techniques and hardware already available.
The innovative part of this project is the utilisation of a slow speed multi pole alternator which will deliver conventional frequency and voltage when directly coupled to the wind turbine rotor. To minimize the excitation demand for the alternator the dominant excitation system will be of a permanent magnet design. The remaining poles will be more conventional electromagnet to allow +/- 10% voltage buck or boost in order to regulate the voltage to maintain a constant output voltage with varying load.
The use of a permanent magnet excitation system avoids the power demand necessary for conventional excitation reducing the losses in such alternators to iron losses and copper losses and since the speed is low, windage losses are negligible so that realizable generation efficiencies of 90% plus are possible in small machines comparable to 70% or so in self excited design. By using both permanent magnet and some 15-20% conventional excitation the overall efficiency will be improved without sacrificing the availability of constant voltage output.
By careful attention to detail the null point of the controlled field can be designed for a specific load to maximize generator efficiency at that load. The fact that a large proportion of the excitation is provided by permanent magnets ensures that excitation cannot fail and electrodynamic braking by connecting a fixed low resistance across the output of the alternator offers a wear free braking system for initial retardation during controlled or emergency stopping of the turbine, reducing wear on the mechanical control and emergency stop braking systems so reducing maintenance requirements and enhancing reliability.
Programme(s)
Topic(s)
Data not availableCall for proposal
Data not availableFunding Scheme
DEM - Demonstration contractsCoordinator
NE46 4TN Hexham
United Kingdom