Motor protection circuit breaker, 40 A, Class 10 — SIRIUS 3RV1042-4FA10
The Siemens 3RV1042-4FA10 is a SIRIUS motor protection circuit breaker rated for 40 A continuous current, delivering 18.5 kW at 400 V AC-3. Screw-type box terminals on the main circuit accept solid conductors up to 2x 16 mm² or stranded up to 1x 70 mm² — sized for the 40 A feed without needing lug adapters.
Breaking capacity drops with voltage: 100 kA at 240 V and 400 V AC, then 18 kA at 500 V, and 12 kA at 690 V. For a 400 V panel with a transformer-fed 480 V secondary, the 18 kA figure at 500 V still covers most industrial service-entrance fault levels. The 690 V rating at 12 kA suits 600 V class North American systems or 690 V European IT networks, but verify the available fault current at the point of installation — if it exceeds 12 kA at 690 V, you need upstream current limitation.
Integration notes
Ground fault detection is not included; if GF protection is required, pair this with a separate ground-fault relay and shunt trip. Power dissipation runs 23 W in hot operating state (7.7 W per pole).