Design and evaluation of performance tester for yaw brakes in wind turbines

In this study, a new type of test equipment is proposed to verify the performance of yaw brakes. A Nacelle, one of the wind turbine unit, rotates every 15 minutes to adjust its position to perpendicular to the blowing wind, which is known for yawing motion. The nacelle contains a main shaft, a gear box, and a generator, so that the size and weight are huge. A yaw brake system is the main device to stop the rotating nacelle during the yawing motion. A big disc of which the diameter is about 2 meters and several brakes are installed at the bottom part of the nacelle. Due to the difficulty of the size, the performance test for the yaw brake is very difficult. New tester is designed using a partial disk to simulate the disk brakes in the nacelle, as well as the application of braking force by a hydraulic actuator located at double the radius of the disk in order to reduce the hydraulic power. The stresses and strains are calculated through CAE analysis, and the values are compared with those from strain gage tests. After verifying the performance of the tester and testing two kinds of brake pads, it is found that alumina and chromite increase the friction coefficients but produce vibration and sound noise.