What it is and what it fits
The Siemens 3RB1036-1QB0 is a solid-state overload relay from the SIRIUS 3RB1 series, rated for 6 to 25 A with a Class 10 trip curve. It mounts directly onto a contactor of size S2 using screw connections, and offers both manual and automatic reset modes. The solid-state design means no bimetal drift over time — the trip characteristic stays consistent across the relay's service life, which matters for repeatable motor protection in production lines.
What the ratings mean for fit
The 6 to 25 A range covers common small-to-medium motor sizes on 400 V three-phase systems. Class 10 means the relay trips within 10 seconds at 600% of the set current — fast enough to protect standard squirrel-cage motors during a locked-rotor condition without nuisance tripping on normal starting inrush. The size S2 contactor footprint is the physical interface: this relay bolts onto the contactor's top or side mounting slots, not onto a DIN rail directly. Screw connections mean field wiring with ring or fork terminals; no push-in or spring-cage tooling required.
Deployment context
This relay is designed for panel-mounting as part of a motor starter assembly — the contactor carries the main power, and the 3RB1 provides the overload protection. The manual-automatic reset selector lets the commissioning engineer choose between latching on trip (manual reset) for attended lines or auto-reset for remote/unattended installations. The solid-state output avoids the mechanical wear of a traditional bimetal relay, so it's a good fit for high-cycle applications like conveyors or pumps that cycle frequently.