What it is and what it does
The Siemens 3RU7136-1KB0 is a SIRIUS size S2 thermal overload relay rated at 12.5 A operational current, designed to protect three-phase AC motor circuits up to 690 V at 50/60 Hz by monitoring motor current and tripping on overload — Trip Class 10 means it will trip within 10 seconds at 7.2× the set current, fast enough for standard induction motor starts without nuisance tripping on normal inrush.
Mounting and integration
Mounts directly onto a SIRIUS S2 contactor via the contactor-mounting fastening method — no DIN rail bracket needed for the basic assembly, though the relay itself has IP20 protection on the front and IP00 at the terminals, so it expects to live inside a panel enclosure. The 118 mm depth and 55 mm width match the S2 contactor footprint; spacing of 6 mm to grounded parts at the side is required for clearance.