Motor Protection Circuit Breaker for 400 V Panels
The Siemens SIRIUS 3RV2031-4PB15 is a motor protection circuit breaker designed for protecting three-phase induction motors against overload and short-circuit. It is rated for Trip Class 20, meaning it allows a 20-second overload duration at locked-rotor current before tripping — standard for general-purpose conveyors, pumps, and fans that don't need the fast trip of Class 10 or the extended ramp of Class 30. The unit breaks 30 kA at 400 V AC, which is the typical SCCR for a 400 V distribution panel feeding motor starters, and it includes phase failure detection as a built-in function.
Breaking Capacity and Coordination
At 400 V, the 3RV2031-4PB15 delivers 30 kA breaking capacity, which is the common requirement for IEC motor control centers backed by a 400 V transformer. At 240 V it rises to 100 kA, and at 690 V it drops to 2 kA — the voltage-dependent curve is typical for this class. The rated operational voltage spans 20 to 690 V AC, so it covers 400 V and 480 V line-to-line systems without derating the voltage rating. The interrupting rating at 500 V is 5 kA, and at 690 V it is 2 kA, which limits application on 690 V systems to low-fault-current scenarios.
Mounting and Panel Integration
Mounts via screw fixing or snap-on onto 35 mm standard mounting rail per DIN EN 60715. The mounting position is any orientation, which simplifies layout in crowded enclosures. Dimensions are 55 mm wide, 140 mm high, and 149 mm deep — the 55 mm width is a single modular unit, so it occupies one 55 mm slot on the DIN rail. Clearance requirements: 50 mm above and below, 10 mm at the sides. Main contact terminals accept M6 bolts, and the conductor cross-section ranges from 2x 0.5 mm² up to 2x 2.5 mm² solid or stranded.
Switching Frequency and Auxiliary Ratings
Maximum switching frequency under AC-3 and AC-3e duty is 15 operations per hour — adequate for motor start-stop cycles in material handling and conveyor applications, but not for high-speed jogging or reversing. Auxiliary contact ratings: 1 A at 24 V, 0.15 A at 60 V, 0.5 A at 230 V. At 110 V, 125 V, and 220 V the rated current is 0 A, meaning no auxiliary contact is available at those voltages — verify the control voltage before specifying.