The Siemens 3RU1146-4KB0-ZX95 is a SIRIUS-brand thermal overload relay in the S3 frame size, designed to protect motors against overcurrent and phase failure by tracking the thermal load through a bimetallic strip. It mounts directly onto a SIRIUS contactor (contactor mounting per), saving DIN-rail space and keeping the power loop short.
The CLASS 10 trip characteristic is the headline spec here. For a motor that takes, say, 6 seconds to accelerate past locked-rotor current, CLASS 10 gives you margin; CLASS 20 would let the motor cook longer, CLASS 5 might trip on a healthy start. Match the trip class to your motor's acceleration time and service factor — this one suits standard general-purpose motors on pumps, fans, and conveyors. Physical fit: 120 mm high, 70 mm wide, 140 mm deep. Mounting clearance: 0 mm upwards, forwards, and backwards, 6 mm at the side. That zero-clearance top and bottom means you can stack contactors and overloads without wasting vertical panel space. Main circuit accepts stranded 2x (10…50 mm²) or solid 10…70 mm²; auxiliary side takes solid 2x (0.5…1.5 mm²) or 2x (0.75…2.5 mm²). AWG equivalents: main 2x (10…1/0) stranded, 1x (10…2/0) solid; auxiliary 2x (20…16) and 2x (18…14). That covers most motor power wiring up to about 30-40 hp at 480 V. Auxiliary contact ratings: 1 A at 24 V, 3 A at 120 V, 2 A at 230 V, 1 A at 400 V. Also rated at 0.22 A for 110 V and 125 V, and 0.11 A at 220 V. These are the normally-open and normally-closed signal contacts that tell the PLC or starter coil whether the relay has tripped. Environmental: IP20 on the front — protected against finger contact, not water. That's standard for inside a cabinet. Operating temperature -20 to +70 °C, storage and transport -55 to +80 °C. Shock rated 8g for 10 ms. Mounting position: vertical surface, rotatable ±135° or tiltable ±45° front/back.
This relay lives inside motor starter assemblies in industrial control panels — protecting three-phase induction motors on pumps, fans, compressors, conveyors, and mixers. The ATEX certification (DMT 98 ATEX G 001,) means it's also approved for use in potentially explosive atmospheres (Zone 1 or Zone 2 gas groups), provided the rest of the starter assembly meets the installation rules. The 100 % relative humidity rating suits it for humid environments like washdown areas or outdoor cabinets, as long as the enclosure keeps direct water off the IP20 front.
ATEX certification (DMT 98 ATEX G 001,) for explosive atmospheres. Substance prohibitance date 07/01/2006 aligns with RoHS compliance — the relay meets the RoHS directive effective that date. Surge voltage resistance rated at 8 kV for insulation coordination per IEC 60947. Protection class IP20 on the front. The SIRIUS series carries UL, CSA, and CE markings standard; specific approvals for this variant should be verified on the nameplate or Siemens declaration.
Integration note
Mounts directly onto a SIRIUS contactor — no DIN rail needed for the overload itself, it clips onto the contactor's output side. The contactor carries the power wiring; the overload's main terminals connect to the motor leads. For standalone mounting, a separate adapter base is available from Siemens. The screw terminals are standard for panel builders: strip, torque, label. No push-in or spring-cage on this variant — factor in screwdriver time.