Fundamental characteristics of circuit breaker – Schneider Electric (Compact NSX – New breed of circuit breakers)The fundamental characteristics of a circuit breaker are:Its rated voltage UeIts rated current InIts tripping current level adjustment ranges for overload protection (Ir or Irth) and for short circuit protection (Im) NOTE: Current-level setting values which refer to the currentoperated thermal and “instantaneous” magnetic tripping devices for over-load and short circuit protection.Its short circuit current breaking rating (Icu for industrial CBs; Icn for domestictype CBs).Rated operational voltage (Ue)This is the voltage at which the circuit breaker has been designed to operate, in normal (undisturbed) conditions. Other values of voltage are also assigned to the circuit breaker, corresponding to disturbed conditions.TopRated current (In)This is the maximum value of current that a circuit breaker, fitted with a specified overcurrent tripping relay, can carry indefinitely at an ambient temperature stated by the manufacturer, without exceeding the specified temperature limits of the current carrying parts. ExampleA circuit breaker rated at In = 125A for an ambient temperature of 40 °C will be equipped with a suitably calibrated overcurrent tripping relay (set at 125 A).
