What it is and what it does
The Siemens 3RU7136-4QB0 is a SIRIUS S2-size thermal overload relay rated for 57 A operational current, protecting three-phase motor circuits up to 690 V AC/DC. Its Class 10 trip characteristic means it will trip within 10 seconds under a locked-rotor condition at the rated current — fast enough to protect standard induction motors without nuisance tripping on normal start-up transients. It mounts directly onto a compatible S2 contactor (no separate DIN-rail bracket needed), saving panel space and simplifying wiring. The screw-type main terminals accept 2x (0.75...2.5 mm²) solid or stranded wire, torqued to 3...4.5 N·m.
Key ratings in context
The 57 A rating is the continuous operational current for AC motor duty. That number, not a higher short-time rating, is what governs the motor FLA it can protect — size the overload for the motor nameplate amps, not the relay's maximum. The 17.1 W typical power loss at rated current means it stays cool enough in a standard IP20 enclosure, but if you're stacking relays side-by-side in a confined panel, check the 6 mm side spacing requirement to grounded parts. Auxiliary contacts handle 3 A at 24 V and 2 A at 230 V, with a DC-13 rating of 1 A at 24 V for solenoid loads. The 6 kV surge voltage resistance (rated impulse withstand) means it can handle typical industrial transients without flashover.
Where it goes and how it fits
This is a contactor-mount overload relay for the SIRIUS S2 platform. It bolts directly onto the output side of a matching S2 contactor (e.g., 3RT7036 series) — no extra wiring between contactor and overload. The assembly then mounts on a DIN rail or panel via the contactor's base. The relay body measures 55 mm wide, 105 mm tall, and 118 mm deep, so it fits standard 600 mm deep enclosures with room for wiring ducts. Mounting position is flexible: vertical surface with ±135° rotation or ±45° tilt front-to-back. Ambient operating range is -20 to +55 °C, with 0...90 % relative humidity (non-condensing). The front face carries an IP20 rating (finger-safe), while the terminal area is IP00 — keep live parts clear of grounded metal.