Motor protection circuit breaker, size S0
Siemens SIRIUS 3RV2021-4FA10-0BA0 is a motor protection circuit breaker in size S0, with Class 10 trip protection. The interrupting ratings are what you need for coordination studies: 100 kA at 240 V, 10 kA at 400 V, 3 kA at 500 V, and 2 kA at 690 V. That 10 kA at 400 V covers most industrial panelboard fault levels without needing upstream current-limiting fuses. Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, in any position. Width is 45 mm.
Panel integration and wiring
Dimensions: 97 mm deep, 45 mm wide, 97 mm tall. The S0 frame accepts screw-type terminals sized for 2×(1…2.5 mm²) or 2×(2.5…10 mm²) solid or stranded copper. Terminal screws are M4, requiring a Pozidriv size 2 tip or a 5–6 mm diameter screwdriver shaft. Clearance requirements: 70 mm upward and downward, 30 mm at the sides, zero forward or backward. The gG fuse backup ratings at 400 V, 500 V, and 690 V are all 63 A — consistent across the voltage range. Rated operational voltage covers 20…690 V. Ambient operating temperature range is -50 to +40 °C; storage and transport range extends to +80 °C. Maximum switching frequency at AC-3 duty is 15 operations per hour.
Protection features
Phase failure detection is built in — the breaker will trip on loss of any phase, preventing single-phasing damage to the motor. Ground fault detection is not integrated; that requires an external module or a separate ground-fault relay.