Emax Low voltage air circuit-breakers - ABB Download Center

Construction characteristicsUtilization category1Selective and current-limiting circuit-breakersSelective (non current-limiting) circuit-breakers are classifiedin class B (according to the IEC 60947-2 Standard). It is importantto know their Icw values in relation to any possible delayedtrips in the event of short-circuits.The current-limiting circuit-breakers E2L and E3L belong toclass A. The short-time withstand current Icw is not very importantfor these circuit-breakers, and is necessarily low due to theoperating principle on which they are based. The fact that theybelong to class A does not preclude the possibility of obtainingthe necessary selectivity (e.g. current-type or time-type selectivity).The special advantages of current-limiting circuit-breakersshould also be underlined. In fact, they make it possible to:– significantly reduce the peak current in relation to the prospectivevalue;– drastically limit specific let-through energy.The resulting benefits include:– reduced electrodynamic stresses;– reduced thermal stresses;– savings on the sizing of cables and busbars;– the possibility of coordinating with other circuit-breakers inthe series for back-up or discrimination.987 6b 6a987 6Caption10111SDC200023F0001Selective circuit-breakerE1 B-N, E2 B-N-S, E3 N-S-H-V,E4 S-H-V, E6 H-V5b5a243110111SDC200024F0001Current-limiting circuit-breakerE2 L, E3 L524311 Sheet steel supportingstructure2 Current transformer forprotection trip unit3 Pole group insulating box4 Horizontal rear terminals5-5a Plates for fixed maincontacts5b Plates for fixed arcingcontacts6-6a Plates for main movingcontacts6b Plates for moving arcingcontacts7 Arcing chamber8 Terminal box for fixedversion - Sliding contactsfor withdrawable version9 Protection trip unit10 Circuit-breaker closing andopening control11 Closing springs1/8ABB SACE