Arc-wall interaction phenomena immediately after contact separation in magnet-blast interrupters

Arc-wall interaction phenomena without and with a baffle plate arranged next the switching contacts opposite to the direction of arc motion were investigated in a model interrupter. The criterion considered was the time of reduced arc motion immediately after contact separation. Arc current geometry of contacts and walls, contact material (Cu, Ag/C, Ag/SnO/sub 2/, Ag/CdO) and the materials of lateral walls and baffle plates (nongassing and gassing) were varied. Both the changes of the wall characteristics (surface resistance and mass loss or gain) and the mass loss of the contacts caused by temporarily immobile switching arcs were measured additionally. The time of reduced arc motion is often influenced by both wall distance and wall material under unfavourable conditions only, depending also on the contact material. Gassing walls usually inhibit initial arc motion more effectively than non-gassing ones. Increasing arc current generally reduces t/sub ram/ (B/I kept constant). A baffle plate influenced the time of reduced are motion merely under unfavourable conditions when arc motion was slow or uncertain In such cases a baffle plate may accelerate the initial arc motion more or less effectively. The surface resistance of the lateral walls may be reduced by metallization (ceramics) or by carbonization (certain organic materials) during the time of reduced arc motion, depending on both wall and contact materials. Ceramic walls (non-gassing) suffered mass gain due to metallization of the surface, gassing (organic) lateral walls showed mass loss depending on the arc stress. The mass loss of the anode was higher than on cathode, both decreased to merely weak, when a baffle plate was applied.