DC breaking tests up to 55 kA in a single vacuum interrupter

DC current breaking tests were carried out on several vacuum circuit-breakers during the design of the energy transfer units for the RFX fusion experiment. The tests were performed with a synthetic circuit able to reproduce the expected stresses on the switching element during the breaking phase. The performance of a prototype for a medium-voltage AC switch with a self-produced axial magnetic field is discussed. The interrupter was found capable of breaking currents up to 55 kA with a recovery voltage greater than 35 kV and high values of di/dt in a large range of arcing times