Influence of the shape of silver contacts on the spatial distribution of spectral intensity of a breaking arc

In a DC 50V/3.3 A circuit, the spatial distributions of the spectral intens ities of breaking arcs near the cathode for silver contacts were measured o n the contact surfaces of three different shapes: flat and spherical (1 mm radius and 2 mm radius) and the are temperature and the metal-vapor quantit y were calculated from the spectral intensities. The influence of the conta ct shape on the are temperature and the metal-vapor quantity were also exam ined, as well as the are tracks on the contact surfaces and the gain and lo ss of the contacts. Findings show the distributions of spectral intensities are non-symmetrical from the beginning to the extinction of the breaking a re for the flat contact: However, they are symmetrical in the latter half o f the breaking in spite of the number of breaking area and the shape of con tact surface for the spherical contact. The relationship between the area o f the are tracks on the cathode and the shape of contact surface is the sam e as the relationship between the existent areas of measured spectra and th e shape of the contact surface. For the spherical contacts, the are tempera ture and the metal-vapor quantity are affected a little by the radius of th e curved of contact surface and the number of breaking arcs. However, the l onger the are duration, the higher the metal-vapor quantity is in the latte r period of the breaking are. For the flat contacts, the metal-vapor quanti ty is lower than those for the spherical contacts. The gain and loss of the contacts are less and the are duration is shorter for the flat contact tha n for the spherical contact.