THE BREAKDOWN PROCESS OF SYNTACTIC FOAM UNDER AC STRESS AT CRYOGENIC TEMPERATURE

Liquid nitrogen (LN2) based insulation systems for superconducting power components are state of the art, but electrically feature some disadvantages. One disadvantage is the significant reduction of the breakdown field strength, if thermal bubble formation within the LN2 occurs during operation. This paper deals with syntactic foam as a solid insulation composite, which can be an alternative to LN2 based insulation systems for superconducting power components. Syntactic foam consists of a polymeric matrix and embedded hollow microspheres with mean diameters of several 10 µm. The embedded hollow microspheres feature a reduced thermal contraction, a lower density and a lower relative permittivity compared to the pure matrix material. Several syntactic foams are investigated regarding their…