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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:uj/uj:3038 |
| Date | 22 August 2012 |
| Creators | Willcock, Peter Richard |
| Source Sets | South African National ETD Portal |
| Detected Language | English |
| Type | Thesis |
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