Field testing of a passive electrodynamic brake for wind turbines

Electrodynamic braking is used widely in industry to control the speed of induction machines, but has not been exploited to any large extent on commercial wind turbines. A wind turbine brake is required to control the aerodynamic rotor speed when the wind speed exceeds the turbine´s design limits, to stop the machine for maintenance and in the event of a fault. Conventional wind turbine brake systems use a combination of aerodynamic and mechanical shaft brakes. Electrodynamic brakes offer a highly repeatable braking performance, with no brake component wear and controllable torque. One reason for the limited exploitation of electrodynamic braking in wind turbines is a lack of proven operating experience. This paper presents the results of field tests of a passive electrodynamic brake connected to a 45 kW fixed speed stall regulated wind turbine at a UK wind test site