An introduction to the circuit breaker tripping curve.
So, If I pulled 6Amps through a 6amp circuit breaker will it trip?
If you said yes then you must hang around this site much more frequently.
So when does a circuit breaker trip then?
Truth is that the cb will operate happily continuously at its rated current at the specified temperature.
A circuit breaker will trip at any value HIGHER then its rated current and the higher the fault current the quicker the circuit breaker will trip.
At 115%In it might trip in a half an hour but at fault current 600%In it might trip in 0.1seconds.
In fact the IEC 60 947-2 standard dictates: A circuit breaker with In > 63Amp, pulling 105%In must not trip in 2hours(for In < 63Amp ->1Hour) at 130%In it must trip within 2hours(In<63Amp ->1Hour)
This tripping characteristic is referred to as “The Inverse Proportional tripping curve”.
Hopefully this makes much more sense.
What does this curve look like? nice surprise! – click on pic to open new.
In = The maximum amount of current a circuit breaker can carry, break/make safely otherwise said – what it is designed for.
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