SIEMENS The performance of ship-to-shore cranes is often limited by vibrations of the crane structure caused by movements of the crab. Passive oscillation dampers with a seismic mass of approximately 30 tonnes are used nowadays on container gantry cranes but only achieve a limited reduction in vibration. A significantly higher damping, which is more or less adjustable by means of drive parameters, can be achieved using the Siemens power drive damper. The following article by Uwe Ladra and Elmar Schäfers from Siemens AG’s Drive Technologies Division in Erlangen, Germany, describes the systematic development of this active damping system with a linear direct drive in which the damping force is directly generated using a linear motor.