What the 50 A AC-3 rating means for your motor branch
The 3RV5331-4HC10 is a SIRIUS circuit breaker sized for starter combinations — the branch protection and disconnect for a motor control center or individual starter bucket. Its headline number is 50 A operational current at AC-3 duty, 400 V. AC-3 is the standard motor-switching category: starting, stopping, and running a squirrel-cage induction motor under full load. So this breaker carries a motor branch up to 50 A steady-state, which for a 400 V three-phase supply translates to roughly 30 kW of connected motor load. The instantaneous short-circuit trip is fixed at 650 A — that's the magnetic element that clears a bolted fault before the overload relay sees it. That 650 A threshold is set at the factory; it's not field-adjustable, so verify your motor's locked-rotor current stays below it to avoid nuisance trips on start.
The S2 frame measures 55 mm wide, 140 mm high, 149 mm deep. Clearance requirements: 50 mm above and below, 30 mm to the sides, 140 mm forward — no clearance needed behind the DIN rail (–). That forward clearance is the space for the box-type screw terminals, which accept 2 x 0.75–25 mm² solid or stranded, or 1 x 0.75–35 mm². Terminal torque spec is 3–4.5 N·m. Mounting position is any, which helps in tight enclosures where the rail is vertical or horizontal.
Operating ambient -20 to +60 °C; transport/storage -50 to +80 °C. Relative humidity 10–95% during operation. Shock resistance 25 g / 11 ms per IEC 60068-2-27. Installation altitude up to 2000 m above sea level. Rated impulse withstand voltage 6 kV. The part carries a substance prohibitance date of 07/01/2006, consistent with RoHS compliance.