Low Voltage circuit-breaker breaking techniques - Schneider Electric

,,,-./012345:;c the former, reinforced by use of energydiscrimination (refer to "Cahier Technique" no.167) is obtained with A category circuit-breakersas in standard IEC 60947-2. These circuitbreakershave to break the fault current veryquickly and considerably limit short-circuitcurrents.c the latter is achieved with B category circuitbreakers.These circuit-breakers, normally themain ones, have to withstand the flow of steadystatefault currents and therefore need anexcellent electrodynamic withstand.Excellent short-circuit current limitation(also refer to "Cahier Technique" no. 163)This is particularly aimed at for circuit-breakersless than or equal to 630 A.These circuit-breakers develop an arcing voltageof 600 to 900 V in small volumes. It is easier toobtain this voltage using double breakingsystems (by combining the diagrams in figures25b and 26b) and by implementing a rotatingtype moving contact which has the addedadvantage of simplifying production of onebreaking unit per pole (see fig. 29 ). ,, ,, upper connectionarc chuteablative part , moving contactenclosurebar ,, ,,,magnetic circuitconnection trip unit Fig. 29: breaking unit of a rotating contact LV circuit-breaker (Compact NS - Merlin Gerin). ?HIJK ## $$ %% && '' (( )) *+,-./0'' ()*+,-- 22 3355678 $$$ %%% &&&(( )) ** ++ ,,-- 444 555 .. /01 99 :: ;; >ABCDEFG// 00 11 22 33Cahier Technique Schneider Electric no. 154 / p.25