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M.Ing. / The use of electronically controlled electrical power equipment, specifically power converters, has rapidly increased in recent years. It has subsequently been found that different electrical equipment, placed or working in close proximity, can negatively influences each other's performance. The degradation in performance could be attributed to mutual electromagnetic interference (EMI). Traditional methods of testing conducted EMI usually follow a black box approach with additional filter elements being added to the converter input to bring it within specification. This study focuses on the conducted electromagnetic interference of a specially built experimental boost converter that would typically be used as a preregulator to improve the power factor. The converter circuit was constructed in a number of functional circuit sections in order to assess an individual section's contribution to the emission and propagation of conducted EMI throughout the converter. The operational behaviour of the converter can thus be systematically studied and improved before additional filter components are added. The measurement standards require that conducted EMI measurements are made at the power source input of the equipment under test. These measurement techniques do not allow a systematic tracing of the propagation of conducted EMI throughout a converter circuit. Since no frequency spectrum measurement is available at any other measurement point in the converter. Part of this thesis was thus devoted to the development of an enhancement to current measurement techniques that enables EMI frequency measurements throughout a converter. A special EMI probe was developed for this purpose. Using this EMI probe conducted EMI propagation can be traced from its source throughout a converter to the power input. An analytical analysis of the boost converter's behaviour, with emphasis placed on its switching transients, was initially undertaken. This was continued with PSPICE® circuit simulation. Various aspects of the converters operational behaviour were considered. The simulation results suggested modifications to the converter switch circuit, which would improve the boost converter's conducted EMI characteristics. These were then evaluated with corresponding practical measurements carried out on the boost converter. The practical results confirm that the converters switching behaviour can be directly related to the parasitic and other components. Improvement of the converter switching behaviour lead to an improvement of the conducted EMI emissions of the boost converter.

M.Ing. / This thesis investigates why electromagnetic interference (EMI) and electromagnetic compatibility (EMC) problems exist and how EMI is generated, measured and limited. This investigation is done with reference to power systems and satellite earth stations. To understand the full extend of EMI generation from power systems on satellite earth stations, it was necessary to do a study of EMI, in order to understand EMI in its simplest form. This study consists of the following work: •A background study investigates the components of EMI, how EMI are generated and manifest in electric systems, methods to limit conducted EMI, a theoretical model on how to estimate conducted EMI quantities and EMI measurement techniques. •A conducted EMI model with which the parasitic impedances could be controlled was developed. With this model it could then be determined how conducted EMI would manifest in 3-wire circuit designs and how conducted EMI could be reduced in such circuits. •It was investigated how inductive coupling and capacitive coupling can be reduced. Time and frequency domain measurements were used to investigate the effects of these couplings. It was also of great importance to understand how EMI from measurement set-ups could influence measurements to give inaccurate results. This work investigated how high frequency measurements can be done effectively, how high frequency circuit designs can be improved and how parasitic impedances can be limited in high frequency equipment. •The expected EMI problem at the Klipheuwel wind farm was analysed. Simulations of expected EMI levels, worst case scenarios and measurements taken there showed that no significant EMI are generated from the wind generators and that power systems don’t hold a threat to satellite earth stations, if the necessary precautions are taken.