Current Limiting MCB's

Maybe on paper. However, as the devices get fuller with  electronics, current transformers and so on, the space for decent arc traps and big springs needed to stretch  & kill an arc fast gets taken up. 
It is harder to dump the same energy in what is in effect a smaller space, so the margin of being better than the absolute minimum required may not be exactly the same. Rather like the 9mm wide MCBs that came and went a few years ago and never seemed to touch the sides, where the PSSC was a bit doubtful. Looking the other way there is a very good reason that MCCBs etc for big fault currents are made as larger sized lumps.

Remember things like this being the device of the future but not actually available ?

To be fair they do claim to have made one that manages 6KA now and I guess the live and neutral breaking RCBOs are similar in terms of contact size and swing to a half size MCB.

Mike.

Maybe on paper. However, as the devices get fuller with  electronics, current transformers and so on, the space for decent arc traps and big springs needed to stretch  & kill an arc fast gets taken up. 
It is harder to dump the same energy in what is in effect a smaller space, so the margin of being better than the absolute minimum required may not be exactly the same. Rather like the 9mm wide MCBs that came and went a few years ago and never seemed to touch the sides, where the PSSC was a bit doubtful. Looking the other way there is a very good reason that MCCBs etc for big fault currents are made as larger sized lumps.

Remember things like this being the device of the future but not actually available ?

To be fair they do claim to have made one that manages 6KA now and I guess the live and neutral breaking RCBOs are similar in terms of contact size and swing to a half size MCB.

Mike.