Low Voltage circuit-breaker breaking techniques - Schneider Electric

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Lexiconα: closing voltage angle.category (of a circuit-breaker): defined bystandard IEC 947.2.A = circuit-breaker not delayed on opening inshort-circuit conditions;B = circuit-breaker delayed on opening in shortcircuit< Icw conditions.E: DC rated voltage, AC peak voltage.ϕ: voltage/current phase angle.i, (i 0): current at an instant t, (at an instant t 0).i a: arcing current at an instant t.î c: broken peak current.Icc: short-circuit current.Ics: rated service breaking capacity (expressedin kA or in % of Icu).Icu: rated short-circuit ultimate breakingcapacity.Icw: rated acceptable short current.In: rated current in steady state, Ar.m.s.Ip: prospective current.Is: overload current.r: generator impedance.R, L, C: total components of broken circuit.rating (of a circuit-breaker): rated current valueof the circuit-breaker, defined by the maximumsetting of the trip unit (electronic or thermaloverload protection).size (of a circuit-breaker): the highest ratingaccepted by a circuit-breaker case. It is therated current of the device.t, (t 0): time (initial instant).t a: arcing time.τ: time constant (τ = L / R).u: voltage at an instant t.u a: arcing voltage at an instant t.U a: stabilised arcing voltage.U AC: Anode-Cathode voltage of eachelementary arc.Ud+, Ud-: regeneration characteristics.Un: rated voltage in AC, V r.m.s.Ur: recovery voltage.Wa: arcing energy.W L0: initial inductive energy for i = i 0.ω: AC pulsation(ω =2πf= 2π/T).Cahier Technique Schneider Electric no. 154 / p.2
LV circuit-breaker breaking techniquesThis Cahier Technique aims to:c define the currents to break in LV installations;c explain a phenomenon which occurs whenever a circuit is opened: theelectric arc;c theoretically analyse the breaking of various currents by the arc placed inthe extinguishing condition;c describe breaking devices and in particular circuit-breakers from atechnological standpoint.Contents1 Introduction 1.1 Definition of currents to break p. 42 The electric arc 2.1 Its formation conditions p. 62.2 Its physical properties p. 62.3 Its electrical properties p. 62.4 Its extinguishing conditions p. 73 Using the arc to break the current p. 94 Breaking steady-state currents 4.1 In DC supply p. 104.2 In AC single-phase supply p. 114.3 In AC three-phase supply p. 125 Breaking prospective currents 5.1 Definitions p. 13(with limitation)5.2 Breaking with limitation p. 165.3 Under DC voltage p. 165.4 Under single-phase AC voltage p. 165.5 Under three-phase AC voltage p. 175.6 The breaking parameters p. 175.7 Fuse breaking technique p. 186 The low voltage circuit-breaker 6.1 Its functions p. 196.2 Its technologies p. 206.3 Its performances p. 247 Conclusion p. 27Bibliography p. 27Cahier Technique Schneider Electric no. 154 / p.3
Page 3: no. 154LV circuit-breakerbreaking t
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 and 28: ,,,-./012345:;c the former, reinfor
Page 29: 7 ConclusionThe future of the arc?T

Low Voltage circuit-breaker breaking techniques - Schneider Electric

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