Electrical Breakdown Characteristics of Supercritical Trifluoroiodomethane-Carbon Dioxide (CF3I-CO2) Mixtures

Supercritical fluids (SCFs), as a new type of dielectric medium, combine highly desirable properties of gaseous and liquid dielectrics, most notably: low viscosity, high heat transfer capability, and high dielectric strength. This paper, for the first time, reports the results of breakdown experiments on the mixture of trifluoroiodomethane (CF3I) and carbon dioxide (CO 2 ) under the supercritical conditions. Experiments were conducted in a 0.1 mm gap under a uniform electric field. The state of substance during experiments was obtained by the calculation from the equation of state (EoS), and by evaluating the optical appearance. The experiment result shows a dielectric strength of the supercritical CF 3 I-CO 2 mixture at an average of 278 kV/mm with a 10% CF 3 I mass fraction. Our experiments also suggest that the dielectric behavior of this supercritical CF 3 I-CO 2 mixture manifests a discontinuity of the dielectric strength near the critical point. This paper indicates the suitability of using supercritical CF 3 I-CO 2 mixture for high power density applications.