What this breaker does for a motor circuit
The Siemens 3RV2021-4BA10-ZW96 is a SIRIUS motor protection circuit breaker designed to protect three-phase induction motors against overload, short circuit, and phase failure. Its CLASS 10 trip curve means it disconnects within 10 seconds at 7.2× the thermal setting — fast enough to protect standard squirrel-cage rotors during a locked-rotor event. The breaker also detects phase failure, so a lost phase on the line side won't cook the winding while the motor tries to single-phase run.
Breaking capacity and coordination
Rated short-circuit breaking capacity hits 100 kA at 240 V and 25 kA at 400 V — that's enough to clear a bolted fault on a 400 V distribution board without upstream fuses needing to coordinate. At 690 V the rating drops to 2 kA, so if you're on a 690 V system, verify the available fault current stays under that. The gL/gG fuse backup ratings (63 A at 400 V, 50 A at 500/690 V) give you a clean Type 2 coordination path for contactor combinations.
Panel fit and mounting
Width is 45 mm, depth 97 mm — fits a standard 45 mm slot on a 35 mm DIN rail per DIN EN 60715. Screw and snap-on mounting means you can clip it onto the rail without tools, then secure with the screw if vibration is a concern. Mounting position is any, so vertical, horizontal, or flat — no derating needed for orientation. Clearance: 50 mm above and below, 30 mm at the sides.
Terminals and wiring
Main circuit terminals are M4 screw-type, accepting 2×(1…2.5 mm²) or 2×(2.5…10 mm²) solid or stranded copper. That's enough for a 10 mm² feed to a motor up to about 10 hp at 460/480 V. The screw terminals are standard for panel builders who prefer a positive clamp over spring cages for high-vibration environments.