CLASS 10 trip curve and motor protection fit
The 3RU1146-4KB0: That's the standard for standard-duty induction motors — pumps, fans, compressors — where the start time stays under 10 seconds. The S3 size matches SIRIUS contactors in the same frame class. Mounting is direct to the contactor — no DIN-rail bracket needed, which saves panel width and wiring labour.
ATEX and coordination — what the approvals mean
ATEX certification DMT 98 ATEX G 001 allows installation in gas-group explosive atmospheres (Zone 1 or Zone 2) when paired with an appropriate contactor and upstream protection. The relay itself is not the isolation device — it's the thermal sensing element inside the motor branch circuit. Short-circuit coordination is defined for gG fuses: Type 2 coordination requires 160 A fuses; Type 1 allows 250 A. This matters when designing selectivity downstream of a feeder breaker — the fuse size determines the let-through energy the relay must survive. Surge voltage withstand is 8 kV, which aligns with IEC 60947-1 overvoltage category III for industrial control panels. No additional surge suppression needed for standard 400 V networks.
Panel fit and wiring constraints
Dimensions are 140 mm deep, 70 mm wide, 120 mm tall. Main circuit terminals accept stranded copper from 10 mm² up to 70 mm² — covers motor leads up to about 160 A full load depending on cable type. Control-circuit terminals take solid 0.5–2.5 mm² or stranded equivalents. Mounting position is flexible: ±135° rotation and ±45° tilt from vertical. This helps when the contactor is mounted on a swing frame or in a tight cabinet where straight vertical isn't possible.
Thermal load and ambient limits
Each pole dissipates 6.3 W at rated current. For a three-pole relay that's 18.9 W total — modest, but add the contactor coil and the combined heat can push a small enclosure past its thermal limit if ventilation is poor. The 100 % relative humidity rating during operation means condensation is tolerated, but the IP20 front face does not protect against hose-down or dripping water — keep it inside the panel.
Auxiliary contact ratings for control circuits
These cover direct PLC inputs or small relay coils without an interposing relay in most 24 VDC or 120 VAC control schemes. At 110 V and 125 V DC the rating drops to 0.22 A; at 220 V DC it's 0.11 A. If the control circuit is DC and above 24 V, check the contact rating against the load — the DC break capacity is significantly lower than AC.
Mechanical robustness for vibrating plant
Shock resistance is 8g for 10 ms. That's adequate for most motor-driven machinery (conveyors, crushers, compressors) but not for high-impact applications like forging presses or drop hammers — those need a separate shock-mounted enclosure.
Compliance documentation
RoHS compliance is confirmed by the substance prohibitance date of 07/01/2006. The IEC 81346-2 reference code F designates the protection function in system schematics. ATEX documentation (DMT 98 ATEX G 001) is available from Siemens for the installation file.