Natural Circulating Flow and Winding Cooling Characteristics for A Self-Cooled Transformer Model Cooled by Perfluorocarbon Liquid.

To develop a new type of self-cooled transformer which uses perfluorocarbon liquid as the cooling and insulating medium, natural circulating flow characteristics of the coolant and cooling characteristics of the windings were investigated using a natural circulating loop composed of a two-dimensional winding model and a cooler. The winding model had three different configurations. Each model included model conductors in which thermocouples and thin heater pins were soldered and wrapped in insulating paper. Circulation flow rates, pressure drops and temperatures in the circulating loop and the windings were measured for different coil heat fluxes and different heights of the cooler center from the winding center. From the results, natural circulating flow characteristics of the coolant and its cooling characteristics in the windings were clarified. Furthermore, a computer program was developed to predict flow rates in the circulating loop and temperature rise of the windings. The program could also calculate pressure drops in the windings and cooler. Comparisons were made betweed experimental and calculated results, and the program gave valid predictions of flow rates in the natural circulating loop and temperature rises of coils in windings.