Fuse in series with a breaker

[calabala]

Can anybody tell me why I do find in many designs a fuse in series with a circuit breaker? Is there many reasons to do that for protection?

 

[SteveWag]

Fuses may be faster and provide protection for semiconductors, or may be used for current limiting to protect the breaker contacts.
Steve

 

[jraef]

The most common reasons are either the current limiting effect because of high available fault current capacity upstream of the breaker, or because you have sensitive electronic devices such as SCRs or maybe diode bridges and the clearing time for a circuit breaker would allow collateral damage. If the fuses are labeled as "semiconductor fuses", then it is the latter.

 

[calabala]

Thanks SteveWag and Jraef for your fast answers!