Operability of Metallized Polypropylene Capacitors under High Pressure

In a research project sponsored by 10 industry partners and the Research Council of Norway, theoretical and experimental work has been done for providing fundamental knowledge to support realization of reliable Pressure Tolerant Power Electronic (PTPE) components and circuits for operation at sea depths down to 3000m. The ambition is to locate the complete power circuit including switching devices like IGBTs, IGBT drivers, capacitors, magnetic components, and various sensors in a pressurized liquid environment, while the main converter control electronics is assumed to be encapsulated in one bar environment. The present paper reports the results from experiments for evaluating pressure tolerance for metallized polypropylene (PP) DC capacitors. Challenges regarding exposure to a pressurized liquid environment and the experimental methods for assessing these challenges are discussed. The interim conclusions from the experiments are presented. The main conclusion from live experiments with the metallized film capacitors in pressure vessels up to 300bar is that pressure tolerant operation is feasible; however, the important property of self-healing is negatively affected.