A Corona Free High Voltage Feedthrough Terminal Design for Electronic Applications

This paper reports the development of an alumina ceramic feedthrough terminal for use on Electronic Components that is corona free to its external flashover voltage. Comparing this flashover voltage to the corona start voltage of similar size conventional terminals, this represents an improvement of more than four to one. The improvement has been gained by shielding the air near the critical mounting flange area with a metalized film on the interior of the ceramic body. The paper describes how this has reduced the system of dielectrics in this critical area to a single dielectric and has minimized the effect of the large difference in dielectric constant between alumina, transformer oil and air. This has been done without a significant increase in the stress carried by the internal insulation. Using this design concept, a 60 KV RMS corona free terminal for use on oil filled components has been designed, tested and is described. A small sulfur hexafluoride filled air-to-air feedthrough terminal, which is corona free to higher than 20 KV RMS and which uses the same principles, is also discussed.