What it is and what it does
The Siemens SIRIUS 3RV2021-4FA10-ZW96 is a motor protection circuit breaker designed to protect three-phase induction motors against overload, short-circuit, and phase failure. Its CLASS 10 trip characteristic means it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect standard IEC motor windings during locked-rotor events. The 10 kA breaking capacity at 400 V is the SCCR the breaker can safely interrupt under a bolted fault; if your panel's available fault current exceeds that, you need an upstream current-limiting device.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The 45 mm width is a standard 2-module footprint — it occupies two 22.5 mm slots on the rail, leaving room for auxiliary contact blocks or a separate contactor alongside. Any mounting position is allowed, so you can orient it vertically or horizontally inside the enclosure. Terminal screws on the main circuit are M4, accepting 2x (1…2.5 mm²) or 2x (2.5…10 mm²) solid or stranded copper.
Key ratings at a glance
Phase failure detection is built in — if one phase drops, the breaker trips, preventing single-phasing damage. The rated insulation voltage spans 20…690 V. Ambient operating temperature range is -20…+40 °C; storage and transport range is -50…+80 °C. Clearances: 70 mm above and below, 30 mm to the side, zero forward or backward — useful for panel layout planning.