Air-break circuit interrupter having magnetically-assisted arc-dividing electrodes

An air-break circuit interrupter comprising:

• a plurality of stacked plates of insulating material shaped to define therebetween a plurality of shallow arc-extinguishing chambers;
• a plurality of electrodes straddling the lower edge of said plates, respectively, and having a generally U-shaped base portion interconnecting a pair of upwardly diverging flat arcing wings extending in said chambers in such a manner that an arc drawn below said plates transversely thereof may eventually divide into a number of elementary arcs upon contact with the lowermost part of said base portion of said electrodes, the diverging wings of adjacent electrodes extending in each chamber causing the corresponding elementary arc to develop in said chamber in an expanding loop so that the path of the current flowing in said electrodes and in said elementary arcs develops substantially in the form of an expanding helix;
• and
• a plurality, one for each electrode, of inserts of ferromagnetic material sandwiched between the upstanding parts of said U-shaped base portion of said electrodes thereby to enhance the migratory movement of the roots of said elementary arcs attached to said electrodes from said lowermost part along said upstanding parts towards said wings.