Trip-signal variant — what the note means
The 3RU2126-4AC0-ZW97 is a SIRIUS size S0 thermal overload relay with an integrated auxiliary contact wired to report a "Tripped" message. Unlike a standard 3RU2 relay where the auxiliary contacts are free for any control logic, this variant dedicates one set to the trip signal — so the PLC or HMI sees a discrete alarm the instant the relay opens on overload, without needing a separate sensing circuit. The trip signal is available at the relay terminals without additional wiring to the contactor auxiliary block.
CLASS 10 trip curve and motor protection
For higher-inertia loads like centrifuges or crushers, a CLASS 20 or CLASS 30 relay would be needed to avoid nuisance trips during start. The thermal bimetallic element compensates for ambient temperature from -40 to +60 °C, so trip accuracy holds in unconditioned enclosures or outdoor cabinets.
Mounting and wiring — contactor snap-on
Fastening method is contactor mounting — the relay snaps directly onto a SIRIUS 3RT2 contactor, eliminating DIN rail space. Dimensions are 84 mm deep × 45 mm wide × 102 mm high, the standard S0 envelope. The auxiliary screw terminals accept a 3.0 × 0.5 mm screwdriver tip. No torque tool needed on the main circuit, which speeds wiring on repetitive panel builds. Power dissipation per pole is 2.7 W — at full load the three poles dissipate about 8.1 W total. In a sealed enclosure with multiple relays ganged, this heat adds up; allow ventilation or derate if ambient exceeds 60 °C.
MTTF at high demand rate is 2,280 years, supporting use in safety circuits up to SIL 2 per IEC 61508 when paired with a suitable contactor.