A frequency converter coverts mains current into 3-phase AC current with variable frequency. If one wants to operate a document shredder with a brushless DC motor, the only option is to convert the AC mains current to DC current. A document shredder needs a particularly efficient and powerful motor to supply the cutter with sufficient energy. The motor can be regulated continuously across the entire speed range. In addition to the frequency converter, the device developed by Kontron Electronics includes a Touch Panel that serves as operating and parameter controller.