Operation of IGBT-Modules in Insulation Liquids - A First Step for Enabling Operation in High Pressure Environments
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- Institutt for elkraftteknikk 
Theory regarding the main components needed in a subsea converter are provided. Focus is spent on the IGBT and pulse testing are described. A safe and fully functional test cell for high voltage single and double pulse tests was constructed and approved for operation by both NTNU and SINTEF Energy Research. A custom wounded air-inductance was constructed at the NTNU-workshop to act as a load for the pulse tests. The insulating liquids MIDEL and Galden are described. Humidity-requirements for the liquids are compared to IEC-standards and chosen at 5% relative humidity in MIDEL and 25% in Galden. Characterization of components and successful high voltage pulse tests was performed. Tests were performed before, during and after liquid exposure. Two IGBTs was tested for a 14 day period, one in MIDEL and one in Galden. Both liquids gave sufficient electrical performance. Galden is regarded as the best filling liquid due to earlier research at SINTEF Energy Research where some material compatibility-issues with MIDEL was found. Modification while constructing the test-cell and during tests are described. Optical communication in MIDEL gave a weakening of the fibre optical-link. In realizing a full size converter with optical communication, it is important to account for these losses when dimensioning the strength of the sender.