Page 2 - B_ELSB_Cat_2022_01_MCBs

1/2 ELECTRICAL INSTALL ATION SOLUTIONS FOR BUILDINGS - TECHNICAL DETAILS 9AKK 107991 A8329
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MCBs technical details
Definitions according to standards for miniature circuit breakers

Rated insulation voltage (Ui) according IEC/EN 60664-1: IEC/EN 60947-2
Root mean square (R.M.S.) withstand voltage value assigned This part of the IEC/EN 60947 applies to circuit-breakers,
by the manufacturer to the equipment or to a part of it, the main contacts of which are intended to be connected to
characterizing the specified (long-term) withstand capabil- circuits, the rated voltage of which does not exceed 1.000
ity of its insulation. V a.c. or 1.500 V d.c..
It applies whatever the rated currents, the method of
NOTE: construction or the proposed applications of the circuit-
The rated insulation voltage is not necessarily equal to the rated voltage of
the equipment which is primarily related to functional performance. breakers may be.
The circuit-breakers are designed for use by instructed
IEC/EN 60898-1 people.
Miniature Circuit Breakers according IEC/EN 60898-1 are
intended for the protection against overcurrents of wiring Rated ultimate short-circuit breaking capacity Icu
installations of buildings and similar applications; they are The rated ultimate short-circuit breaking capacity of
designed for use by uninstructed people and for not being a circuit-breaker is the value of ultimate short-circuit
maintained. This part of IEC/EN 60898 applies for a.c. air- breaking capacity assigned to that circuit-breaker by the
break circuit-breakers for operation at 50 Hz or 60 Hz, manufacturer for the corresponding rated operational
having a rated voltage not exceeding 440 V (between voltage. It is expressed as the value of the prospective
phases), a rated current not exceeding 125 A and a rated breaking current, in kA (r.m.s. value of the a.c. component
short-circuit capacity not exceeding 25.000 A. in the case of a.c.).
As far as possible, it is in line with the requirements
contained in IEC/EN 60947-2. The sequence of operations shall be: O – t – CO.*

Rated short-circuit capacity (Icn) Rated service short-circuit breaking capacity Ics
The rated short-circuit capacity of a circuit-breaker is the The rated service short-circuit breaking capacity of a circuit-
value of the ultimate short-circuit breaking capacity breaker is the value of service short-circuit breaking
assigned to that circuit-breaker by the manufacturer. capacity assigned to that circuit-breaker by the
The sequence of operations shall be: O – t – CO.* manufacturer for the corresponding rated operational
voltage. It is expressed as a value of prospective breaking
Service short-circuit capacity (Ics) current, in kA, corresponding to one of the specified
A circuit-breaker having a given rated short-circuit percentages of the rated ultimate short-circuit breaking
capacity has a corresponding fixed service short-circuit capacity and rounded up to the nearest whole number.
capacity (Ics). This is therefore generally not indicated. It may be expressed as a % of Icu (for example Ics = 25 % Icu).

Rated operational voltage (Un) The sequence of operations shall be: O – t – CO – t – CO.*
The rated voltage of a circuit-breaker is the value of voltage,
assigned by the manufacturer, to which its performance * The following symbols are used for defining
(particularly the short-circuit performance) is referred. the sequence of operatons:
The same circuit-breaker may be assigned a number of rated O represents an opening operation.
voltages and associated rated short-circuit capacities. CO represents a closing operation followed by an auto-
matic opening.
2The voltage which appears across the terminals of a pole of t represents the time interval between two short-cir-
a circuit-breaker after the breaking of the current. cuit operations.
The value of the power frequency recovery voltage shall be
equal to 110 % of the rated voltage of the circuit-breaker un-
der test.