The Siemens 3RB1046-2UB0 is a solid-state overload relay rated 15...50 A with a Class 20 trip curve, designed to mount directly onto a contactor. It uses screw connections and is sized as S3, with a manual-automatic reset selector. This is a current-production part, so it's still a standard BOM line item, not a last-time-buy scavenger hunt.
This relay mounts onto the contactor, not on a DIN rail — it's a direct-add-on thermal-magnetic replacement in solid-state form. The screw terminals accept standard power wiring, and the manual-automatic reset selector lets you choose between a latching trip (manual reset) and a self-resetting mode for remote or unattended installations. The S3 footprint is common across the 3RB1 series, so swapping in a different current range later doesn't require re-wiring the contactor.