What It Is and Where It Fits
The Siemens 3RB2143-4ED0 is a SIRIUS solid-state overload relay for three-phase motor protection. It mounts directly to a contactor (contactor mounting), so it integrates into a motor starter package on a DIN-rail or panel backplate without extra bracketry. Three poles for the main current circuit, with screw-type terminals on the power side and spring-loaded terminals on the auxiliary/control side. The auxiliary terminals accept 2x (0.25–1.5 mm²) solid or finely stranded with ferrule, which covers common control-wiring sizes.
Trip Class Adjustability — What It Means for Motor Protection
Trip class is adjustable across CLASS 5E, 10E, 20E, and 30E. That means you set the maximum time the relay allows locked-rotor current to flow before tripping — 5 seconds for fast protection (e.g., submersible pumps), 30 seconds for high-inertia loads (e.g., centrifuges or large fans). One relay covers multiple motor start profiles, reducing SKUs on the shelf.
Environmental and Electrical Robustness
Rated for 100 % relative humidity during operation, so it handles condensation-prone enclosures without derating. Operating temperature range is -25 to +60 °C, storage/transport from -40 to +80 °C. Shock resistance is 15g / 11 ms, typical for industrial panel vibration. Surge voltage resistance rated at 8 kV, and EMC burst immunity meets IEC 61000-4-4 severity level 3 (2 kV on power ports, 1 kV on signal ports). That means it's unlikely to nuisance-trip from switching transients on the same panel bus.
Compliance and Approvals
Carries ATEX certification PTB 06 ATEX 3001 Ex II (2) GD, so it's approved for use in potentially explosive atmospheres — zone 2 gas and zone 22 dust applications when paired with an appropriate motor. RoHS compliance date is July 1, 2006, covering the EU directive.
Physical Fit and Mounting
Dimensions: 70 mm wide, 106 mm high, 124 mm deep. Mounting position is any orientation. Clearance: 0 mm upwards, forwards, backwards, and downwards — so it can be stacked directly against adjacent devices without air gap. Side clearance is 6 mm, which is typical for finger-duct or wire-bundle routing.