What's with the minimum voltage rating on *some* IEC 60947-2 MCBs?

Question

It seems that some, albeit not all, miniature circuit breakers have a minimum voltage rating under the IEC 60947-2 scheme (often 12VAC/DC). For instance, see the Sprecher/Schuh L8 series (PDF page 8) as compared to, say, a Schneider Electric Multi9 C60SP which has no documented minimum voltage rating under IEC 60947-2 (I'm using the C60SP here as it's UL1077/IEC, like the Sprecher/Schuh L8, but the C60BP UL489/IEC breaker lacks a minimum voltage rating as well.)

Why is this? Is this a limitation of testing, or of certain breaker designs compared to others, or of the external environs?

Answer 1

My interpretation is that there is no minimum voltage and thus not stated but like all contacts >2A there ought to be a minimum current for contact wetting or if non gold alloy plated.

The suitability for low voltage however is usually the over current ratio threshold for a rapid trip.

The Schneider specs of 5x breaker current are similar to the type B MCB’s in this regard as specified suitable for low voltage type PLC’s.

Being thermal-magnetic breakers they have a tighter tolerance for slow over-current from a thermal trigger and a wider over-current spec for more rapid magnetic response.