Screening test of relays used under pressurized sulfur hexafluoride (SF)

Kutsukake, Kenichi ; Matsuda, Makoto  ; Hanashima, Susumu; Obara, Kenjiro*

Many measurement and control equipment is installed inside of a high voltage terminal of the JAEA-Tokai tandem accelerator and operated under pressurized sulfur hexafluoride (SF) of 0.5 MPa. This screening test has been carried out to select a relay, which is usable under the SF for turn on and off a power supply of the devices, from commercial relays used in the atmospheric condition. Four kinds of relay were tested: electromechanical relay (EMR), magnet contactor (MAG), solid-state relay (SSR) and hybrid relay (HYB). Temperature of the relay, change of appearance of the relay including contact surface using the SEM and EDS were measured and observed. The EMR and the MAG showed irregular contact because of the sulfide or fluoride, and these compounds which are formed by chemical reaction between metals and sulfur or hydrogen fluoride due to dissociation of SF in electric arcs. Solid-state relay and hybrid relay are available in the pressurized SF of 0.5 MPa.