EMC udgangsfilter for motorstyringer/EMC Output filters for Adjustable Speed Drives

The intensive use of power converters and other non-linear loads in industry and by consumers produce electromagnetic interference (EMI). It is often the case to have very low power sensitive equipment, such as communication receivers, computers, navigation equipment like GPS, medical equipment, near high and medium power converters. In such cases interference often happens with the most unwanted results. The presence of high frequency disturbances in power lines often results in operation failures of electronic equipments that are more and more sensitive because they include microelectronic control systems that work at very low energy levels. The fast switching devices generate high voltage slew rates (dv/dt) and high common-mode voltages, causing some serious problems such as premature winding failures, ground leakage currents, shaft voltages and bearing currents causing the shortening of the bearing's lifetime. One of the solutions for damping these negative effects is the installation of filters at the output of the power converters. The goal of this project is to analyze the use of different types of output filters for power converters and to propose usable and reliable solutions for damping electromagnetic interference. An ideal drive system is targeted which is compatible with all grid systems, has low cost and small size radio-frequency interference (RFI) filters and has no restriction on motor cable length and no screened cables are needed. Such a solution would drastically decrease installation and maintenance costs of adjustable speed electric drives. The project evaluates the state of the art in this area and analyses known solutions for damping electromagnetic interference. An analysis of the usability of the known solutions is made as well. A high-frequency model of the whole electric drive system will be developed. The project will also seek for new possible solutions for damping EMI by using output filters. Different output filter topologies will be developed, simulated and compared. Several different solutions will be considered, like active filters and passive filters. An analysis of the filter'xs impact on the complete drive system will be done and validated also by some practical testing. The performance of the filters will be measured and compared against standards that have to be followed by industry producing power drive systems. All the results will be compiled and the final thesis will be prepared based on these results. The project is supported within the Industrial Fellowship programme by the Danish Academy for Technical Sciences (ATV) and is a result of close co-operation between industry and academia, respectively Danfoss Drives A/S and Aalborg University. (Norbert Hanigovszki, Danfoss Drives A/S, Frede Blaabjerg; Jørn Poulsen, Danfoss Drives A/S)