The Siemens 3RU6126-1KB0 is a SIRIUS thermal overload relay sized for motor protection in the 9–12.5 A adjustable range, Trip Class 10, meaning it trips within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts. Rated for 690 V insulation class with a 6 kV surge withstand, it handles standard 400/480 V motor circuits with headroom to spare.
Fastens directly to the contactor via the provided clip — no additional bracket. Side spacing to grounded parts needs 6 mm minimum for heat dissipation. Main circuit wiring accepts 2×(0.5–1.5 mm²) or 2×(0.75–2.5 mm²) solid/stranded, or AWG 16–12 / 14–8. Auxiliary contacts take 2×(0.5–1.5 mm²) or 2×(0.75–2.5 mm²) as well. Tightening torque for main terminals is 2–2.5 N·m.
Relative humidity tolerance is 0–90% non-condensing.