VI. Hollow Hub & Spinner with Pitch System

Different from many other systems, the electrical pitch control motors are attached to the outside of the cast iron hub, between the hub and the spinner. The room in the hub is thus easily accessible and nearly empty and allows the repair and replacement of the motors. The pitch controller boxes are also not placed into the hub or between hub and spinner, but are located on the inside of the generator stator, where the battery packs for emergency power supply of the DC motors are also located.
The pitch control system allows the individual regulation of each blade for optimum uplift, and the turning of the blades out of the wind in case of a typhoon or because of network demands. A secondary bolt-type locking system can then secure the blades in this position, together with a large disc brake which also sits in the generator. As in nearly all modern turbines, the AV 928 – 2.5 MW is an upwind design with the hub in front of the tower.