The Siemens 3VU2915-0H is a phase separator designed specifically for the 3VU2.1, 3VU2.2, and 3VU2.3 motor-protective circuit-breaker frames. It physically isolates the outgoing power conductors between phases within the enclosure, maintaining the required creepage and clearance distances for the rated voltage class. If you are building or servicing a panel with these breakers, this is the inter-phase barrier that keeps the assembly code-compliant and prevents phase-to-phase tracking.
Integration note
These separators snap into the 3VU2.1, 3VU2.2, or 3VU2.3 breaker base after the power conductors are terminated. They occupy the space between the outgoing terminals and the enclosure wall, so verify that your panel depth and gland-plate clearance accommodate the added projection. No special tooling required — the separator clips into the molded slots on the breaker housing.