What are Parameters of the Circuit Breakers?

There are different essential parameters of the circuit breakers which necessary to understand. Furthermore, These parameters we often see marked on circuit breakers.

The characteristics of circuit breakers mainly include: rated voltage Ue; rated current In; overload protection (Ir or Irth) and short-circuit protection (Im) trip current setting range; rated short-circuit breaking current (industrial circuit breaker Icu; household circuit breaker Icn) )

Operating Voltage (Ue)

It is the voltage at which any circuit breaker is designed under normal conditions.

Rated current (In)

This is the maximum value of current that a circuit-breaker, can carry indefinitely at an ambient temperature designed by the manufacturer, without any interruption.

Read Also: How to Read Nameplate of MCB (Miniature Circuit Breaker)?

However, These are the parameters which need to understand by every electrical engineer.

Overload Trip (Ir) Setting:

It is used for the continuous ampere rating according to current. Moreover, It has different set of multiples in the adjustable knob ranging from 0.4 to 1 of nominal or rated current of circuit breaker which can be represented by In.

Figure 1: Parameters setting knobs
Figure 1: Parameters setting knobs


Ir= multiple *In.


Let suppose we have a circuit breaker having rating of 2000 A which has a current load of 1000A so we will set it 1000A by moving the knob at 0.5 which means

Ir= 0.5*2000
Ir = 1000A

Hence, After exceeding 1000A of load it will trip the Circuit Breaker and will disconnect the load.

Short-circuit relay trip current setting value (Im):

The short-circuit trip relay (instantaneous or short delay) is used to quickly trip the circuit breaker when a high fault current value occurs, and its trip limit Im.

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