Understanding Current Limiting Circuit Breakers

[Pitt123]

Can someone please provide me with an explanation or a reference on how current limiting circuit breakers work.

Some questions I have are what is defined as the current limiting region, and what is the "Let Through Current"?

I saw somewhere that one way these breakers can limit current is by creating an arcing current which acts to create an impdedance in the circuit to lower limit the fault current. I'm not sure if this is indeed how these breakers act.

Also can someone please comment how these breakers would appear on a TCC plot or what effect they would have on the TCC plot and other breakers on the same plot?

 

[richxtlc]

A current limiting circuit breaker is a high speed breaker that can open in 8.3 mS or less, thereby limiting the current through the circuit because it never reaches the peak Short Circuit current.
The let-through current is the current that will actually flow through the circuit. These breakers has special TCCs that show what the let-through current is for an available short circuit current. In the current limiting range, high short circuit current you can see the reduction, in the lower current ranges, the current is about the same as the short circuit current. See this site for more info:
http://www.bussmann.com/library/Docs/UseofLowVoltage.pdf

 

[Pitt123]

A current limiting circuit breaker is a high speed breaker that can open in 8.3 mS or less, thereby limiting the current through the circuit because it never reaches the peak Short Circuit current.
The let-through current is the current that will actually flow through the circuit. These breakers has special TCCs that show what the let-through current is for an available short circuit current. In the current limiting range, high short circuit current you can see the reduction, in the lower current ranges, the current is about the same as the short circuit current. See this site for more info:
http://www.bussmann.com/library/Docs/UseofLowVoltage.pdf

Thanks I will read this article.

Does the avaliable short circuit current vs peak let through curves look the same for breakers as they do for fuses?