. The Bell System technical journal . it used in most of thiswork. All coils used have air cores. When the contacts are closed, a steady state current lo = E/R isestablished in the circuit. At the first physical separation between thecontacts, the circuit current will charge the capacitance C causing a^oltage rise at the contacts at an initial rate of lo/C. In the meantime,the separation between the contacts will increase. The first breakdownwill occur when the voltage across the contacts first reaches or exceedsthe arc initiation voltage corresponding to the separation attained, theatmosphere
. The Bell System technical journal . it used in most of thiswork. All coils used have air cores. When the contacts are closed, a steady state current lo = E/R isestablished in the circuit. At the first physical separation between thecontacts, the circuit current will charge the capacitance C causing a^oltage rise at the contacts at an initial rate of lo/C. In the meantime,the separation between the contacts will increase. The first breakdownwill occur when the voltage across the contacts first reaches or exceedsthe arc initiation voltage corresponding to the separation attained, theatmosphere in^ol^■ed and the contact surface condition. Fig. 2 representsdiagrammatically the occurrence of the first discharge, abc is the arcinitiation voltage versus separation line for a normal contact. The COIL CABLE E^ JL _L CONTACT I (a, ^ ^ I L R I I ^WT^ vVv 1 ^WO^ 1 E^ ^C CONTACT ^ . O . - . - Fig. 1 — (a) Tjpical relay circuit in i)racticc. (b) Linear circuit used in thisstud3\ 538 THE BELL SYSTEM TECHNICAL JOURNAL, MAY 1954. CONTACT SEPARATION Fig. 2 — Initiation of the first arc between contacts on break of an inductivecircuit. portion be corresponds to the sparking potentials in the atmosphere,ab corresponds to the range of small separations, of the order of or lessthan the mean free path of an electron in the atmosphere, where the arcis initiated by field emission through the influence of surface contamin-tions or films. As was shown in Reference 2, when the cathode surfacewas carefully cleaned, the constant field line was not obtained and thearc was initiated at the minimum sparking potential of the occurred on the sides of the contacts along a path much longer thanthe minimum separation between the contacts.* Lines 0-1 and 0-2 represent the voltage rise at the contact with smalland large shunt capacities. Points 1 and 2 are the respective first dis-charge points. In the first case, the arc is initiated at a smaller separationand higher field strength
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Keywords: ., bookcentury1900, bookdecade1920, booksubjecttechnology, bookyear1
