This 3RU2126-4FB0 is a SIRIUS thermal overload relay, size S0, Class 10. It mounts directly onto a contactor – no extra bracket. The integrated auxiliary contacts send a 'Tripped' message back to the PLC or annunciator when the bimetal strips pop the mechanism. That's the note on the line: it's built to signal a fault, not just protect the motor.
Sourcing & lifecycle – still a standard line item
Current lifecycle stage. No end-of-life notice or last-time-buy. Order through standard distribution. The auxiliary contact note 'for message Tripped' means the relay comes with a built-in changeover contact (NO+NC) wired to terminals for remote indication. The screw terminals are sized for 2x 0.5…1.5 mm² or 2x 0.75…2.5 mm² solid/stranded wire. Use a Pozidriv PZ2 screwdriver, shaft diameter 5-6 mm.
Mounting & dimension notes
That's a tidy S0 footprint. Mounts in any position – no derating for side-by-side in open air, but if you pack them tight in a cabinet, watch the ambient inside. The relay compensates for temperature from -40 °C to +60 °C, so it won't nuisance trip on a hot afternoon in a tight panel. Power dissipation per pole is 3.2 W at rated current. For a three-phase motor that's about 9.6 W total – nothing a standard DIN rail enclosure can't shed. Plenty of margin even if the part sits in a cold warehouse before install.