What it is and what it does
The Siemens 3RV1373-7GN10 is a SIRIUS molded-case circuit breaker (MCCB) designed specifically for starter combinations — meaning it integrates into motor starter assemblies where the breaker provides branch-circuit protection and the contactor handles switching. It's a 3-pole unit rated 400 A continuous current, with an electronic short-circuit trip that gives you adjustable magnetic pickup, not a fixed thermal-magnetic curve. Breaking capacity is the headline: 120 kA at 400 V AC, 100 kA at 240 V, 85 kA at 500 V, and 70 kA at 690 V. That 120 kA at 400 V means it can safely interrupt a fault current up to 120,000 amps without welding contacts or venting plasma — critical for high-fault panels downstream of a large transformer. The AC-3 motor-switching rating goes up to 690 V, and the maximum operating frequency is 15 operations per hour, so this is a protection device, not a cycling switch.
Mounting and integration
Mounts via screw fixing — no DIN-rail clip on this frame size. Clearance requirements: 0 mm backwards and 0 mm at the side, so you can pack it tight against the back panel and adjacent devices. Overall dimensions are 205 mm high, 140 mm wide, 103.5 mm deep. That 103.5 mm depth is the body only; factor in the screw-terminal projections for the main and auxiliary circuits. Main circuit terminals are screw-type, same for the auxiliary/control circuit. The breaker accepts auxiliary switch add-ons (product extension auxiliary switch: Yes), though this base unit ships with zero built-in auxiliary contacts — 0 NO, 0 NC, 0 changeover. If you need status feedback, order the auxiliary switch block separately and snap it on. IP20 on the front, finger-safe touch protection per the standard. That's fine for an enclosed panel; not rated for washdown or outdoor exposure. Mounting position is any orientation, which helps in tight retrofit layouts.
Environmental and compliance
Operating temperature range is -25 to +60 °C; storage and transport handle -40 to +70 °C. Shock resistance is 12g for 11 ms. Rated voltage range is 20 to 690 V AC, surge voltage resistance rated at 8,000 V.