The Siemens SIRIUS 3RB2113-4SB0 is a solid-state overload relay for three-phase motor protection, mounting directly onto a contactor. Its adjustable trip class — selectable between CLASS 5E, 10E, 20E, and 30E — lets you match the thermal curve to the motor start profile: 5E for fast-starting servo or spindle drives, 30E for high-inertia loads like centrifuges or large fans. The relay carries ATEX Ex II (2) GD certification, so it's cleared for use in potentially explosive atmospheres when paired with an appropriate motor and upstream protection.
Fastening method is contactor mounting — the relay clips directly onto the contactor's front face, saving DIN-rail space and keeping the power loop short. No upwards, forwards, backwards, or downwards clearance is required around the relay body; only 6 mm at the side is needed for airflow and wiring access. The 45 mm width and 64 mm height match the standard SIRIUS contactor footprint, so it fits existing panel layouts without re-drilling. Screw-type terminals on both the main current circuit and the auxiliary/control circuit accept solid conductors from 0.5 to 4 mm² (2x 0.5 to 2.5 mm²) or AWG 18-14 for the mains, and 2x AWG 20-14 for the auxiliaries.
Electrical ratings and environment
The auxiliary contact set is rated for switching at several common control voltages: 2 A at 24 V, 4 A at 120 V, 3 A at 230 V, and derated figures for 60 V (0.55 A), 110 V (0.3 A), 125 V (0.3 A), and 220 V (0.11 A). The relay operates across -25 to +60 °C and can be stored or transported from -40 to +80 °C. It withstands 100 % relative humidity during operation and shock loads of 15g for 11 ms. EMC immunity includes burst transients at 2 kV on power ports and 1 kV on signal ports, severity level 3 per IEC 61000-4-4, plus a surge voltage withstand of 6 kV.