The ABB 1SDA038306R1 is an undervoltage release purpose-built for the Emax and breaker frames.
Listed as current production. This is an active catalog item, not a phase-out or last-time-buy part. No official successor exists because none is needed — it is the current design.
What the 24V DC rating means in practice
The 24V DC coil is the standard control voltage for most industrial panels — matches PLC digital outputs and 24V power supplies common on DIN-rail. The undervoltage release monitors this bus; if it drops below roughly 70% of nominal (typical dropout), the solenoid releases and the breaker opens mechanically. Because it is a mechanical latch release, not an electronic trip unit, it does not need its own auxiliary power once the breaker is closed. The 24V DC only holds the trip latch; the opening energy comes from the breaker's own spring mechanism.