Design of a measuring system to analyze the power transmission in the slip ring system in double fed induction generators (DFIG)

Large percentages of wind power plants are using double-fed induction generators (DFIG). The slip ring apparatus in DFIGs is used to transfer the rotor current from the rotating to the static part of the generator. During transfer of current, micro brush fires occur in contact area, caused by the separation of brush and slip ring. As a result of the discharge of electric arc energy, temperature rises in area of contact. This phenomenon is largely influenced by the electromagnetic forces, the radial eccentricity, the electro-hydrodynamic and the mechanical forces. In addition, the increased temperature in the contact area influences the wear of graphite brushes. To investigate these influences in our slip ring apparatus on the exciting of the micro brush fires, a Field Programmable Gate Array (FPGA)-based measuring system and software is designed. This system helps us to gauge the relevant measured variables and to characterize the micro brush fires. The measurement system communicates with the computer via the programs (C⁺⁺ and Labview). The C⁺⁺-program is used to transfer the data via the Universal Serial Port (USB). The program Labview communicates with the C⁺⁺-part via TCP-IP to configure the FPGA and to visualize these data.