Utveckling av mätsystem för termisk studie av transformator

Abstract: The main limiting factor with respect to continuous power handling in electrical machines and transformersis the temperature rise in the windings. Thermal models are therefore a valuable tool in thedesign process to be able to predict the operational temperature at certain operating points. To beable to construct such models, an accurate measurement system is needed to obtain the temperaturein several positions over the test object.This report describes the construction, calibration and evaluation of such a system. The systemhas eight channels where each channel is made up by of resistance thermometers, wheatstone bridgeswith amplification and separate data handling process. All testing are done on an ETD ferrite corewith only one winding connected to a DC voltage supply. As a part of the objective of this report, theresults from the measurements shall then be analysed to obtain thermal properties for the test object.Regarding accuracy, the system performs well and the temperatures registered can be trusted. Dueto very similar temperature levels in windings, they can be modelled as one part. The most importantthermal resistance is between the surface of the object to the ambient air. A simple model is thenconstructed and tested.