Calorimetric apparatus for measurement of power losses in capacitors

A calorimetric apparatus has been designed especially for measurement of losses in capacitors. The original feature of this determination of capacitor losses lies in the use of the isothermal calorimetry and in the measurement of an electrical power and not of a temperature rise. The accuracy of the method is very good and is independent of the value of the capacitor dissipation factor, it is very useful for capacitors with very low losses. The Equivalent Series Resistance of polymer film capacitors, using polypropylene, polycarbonate, and polyethylene terephtalate, have been determined under rated voltage, in the rang 1 kHz-1 MHz, between 220 K and 370 K. The losses in the dielectric material have been separated from the losses in the metallic parts and their variations with temperature and frequency have been studied. Unlike electrical devices, the calorimetric apparatus allows us to carry out measurements of power losses in capacitors used for power electronic application (filtering, decoupling), under non-sinusoidal applied voltages.