October 3, 2003 [SolarAccess.com] A new device aims to alleviate some of the stresses that wind turbines are subjected to during prolonged use. Wind blows at variable strengths, shaking the rotor blades and causing frequent variations in the mechanical load. The change in the torque acting on the drive shaft leads to vibrations which can eventually damage the shaft, the shaft couplings and the gear. For this reason, manufacturers and operators of wind turbines need sensor systems to monitor the load and provide advance warning of signs of impending failure. A “watchdog” has been developed by the German Fraunhofer Institute for Industrial Mathematics ITWM in collaboration with a sensor manufacturer, assisted by the Institute for Electrical Machines, Drives and Power Electronics at the University of Dortmund. The sensor makes use of what is known in technical parlance as the magnetostrictive effect: The magnetic properties of the steel components vary according to the applied mechanical forces, such as mechanical torque. The sensor induces a magnetic field, for instance in the rotating shaft. Four coils measure the resulting changes. These data are processed to obtain a measurement of the torsion.