Low Voltage circuit-breaker breaking techniques - Schneider Electric

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It is thus possible to break 100 kA in 2.5 msusing a 250 A circuit-breaker.Excellent electrodynamic withstandThis is aimed at for circuit-breakers equal to orgreater than 800 A.This aim requires compensation ofelectromagnetic forces, which is easier to achievewith simple breaking (diagram 24b) all the moreso since the wide opening (distance betweencontacts) of these larger devices (importance ofconductive parts for high current flow) alsoenables a high arcing voltage (600 to 900 V) tobe obtained.A 3200 A circuit-breaker thus breaks "100 kA" in15 ms (without tripping delay) as well aswithstanding 75 kA for 3 s (see. fig. 30 ).Proven performancesCircuit-breaker performances are evaluated andguaranteed by the carrying out of standardizedtests (refer to IEC 60947-2 and NF C 63-120 ).Thus, with respect to "breaking", tests are usedto verify for example:c endurances under In,c overload endurances (e.g. under 6 In),c breaking capacities by cycles :v O-FO at Icu, ultimate breaking capacity,v or O-FO -FO at Ics, service breaking capacitywith Ics ≤ Icu.Note:The publication of standard IEC 60947-2,dealing with industrial LV circuit-breakers, is thesubject of "Cahier Technique" no. 150 whichcompletes the details given above.arcing horntemporarycontactsarc chute ,,, ,, Ag based maincontacts , ,,,,upperterminal poles shaftactivated by theO-CO mechanism ,,, ,,, lower terminalinsulatingcurrent transformerpole cageconnected toelectronic trip unit Fig. 30: breaking unit of a LV circuit-breaker with excellent electrodynamic withstand (Masterpact - Merlin Gerin). Cahier Technique Schneider Electric no. 154 / p.26
7 ConclusionThe future of the arc?The electric arc continues to be an excellentmeans of breaking with current limitation in lowvoltage.Moreover, low voltage circuit-breakers havebeen considerably enhanced as a result ofdevelopments in know-how, materials and use ofelectronics.For many decades to come, electric circuitprotection will therefore continue to requirecircuit-breakers with «arc control».BibliographyStandardsc IEC 60947-2: Low-voltage switchgear - Part 2:circuit-breakers.c IEC 60050: International electrotechnicalvocabulary.c NF C 63-120 (French Standards): Appareillageà basse tension - 2ème partie : disjoncteurs.Cahiers Techniques Schneider Electricc Development of LV circuit-breakers tostandard IEC 947-2.Cahier Technique no. 150E. BLANCc LV breaking by current limitation.Cahier Technique no. 163P. SCHUELLERc Energy based discrimination for low voltageprotective devices.Cahier Technique no. 167R. MOREL - M. SERPINETCahier Technique Schneider Electric no. 154 / p.27
Page 3 and 4: no. 154LV circuit-breakerbreaking t
Page 5 and 6: LV circuit-breaker breaking techniq
Page 7 and 8: high, but ceases to be of any help
Page 9 and 10: a: composition of the arc columnb1:
Page 11 and 12: 3 Using the arc to break the curren
Page 13 and 14: c if U a = E then Wa/W L0 = 2 only!
Page 15 and 16: 5 Breaking prospective currents (wi
Page 17 and 18: 5.2 Breaking with limitationThe exp
Page 19 and 20: 5.5 In a three-phase AC systemTwo c
Page 21 and 22: 6 The low voltage circuit-breakerA
Page 23 and 24: ⇒The contactsLV circuit-breaker c
Page 25 and 26: ⇒Arcing voltage when splitting oc
Page 27: ,,,-./012345:;c the former, reinfor

Low Voltage circuit-breaker breaking techniques - Schneider Electric

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