What it is and what it protects
The Siemens SIRIUS 3RV1021-0FA15 is a motor protection circuit breaker designed for the main current circuit, with a continuous rated current of 0.5 A and a Trip Class 10 characteristic. That Class 10 rating means it will trip within 10 seconds at 7.2× rated current — fast enough to protect a standard induction motor winding from locked-rotor heat buildup, but with enough inrush headroom to avoid nuisance trips on start. At 400 V AC it delivers 100 kA breaking capacity, and that figure holds across the voltage range up to 690 V AC — 100 kA at 240 V, 400 V, 500 V, and 690 V. That is a consistent fault-clearing capability that covers most industrial low-voltage distribution systems without needing an upstream current-limiting device. Phase failure detection is built in, which is the standard for motor-protection breakers in this class. No ground-fault detection here — that is handled separately if your circuit requires it.
Mounting and panel fit
Mounts via screw or snap-on onto a 35 mm DIN rail per DIN EN 50022, in any position. The 45 mm width and 97 mm height are standard for the SIRIUS 3RV2 frame — it occupies one 45 mm module on the rail. Depth is 96 mm from the rail surface to the front of the breaker. IP20 on the front means it is protected against finger contact, but it is not sealed — install inside an enclosure rated for the environment.
Terminal wiring
Main circuit terminals accept solid conductors 2x (0.5... 1.5 mm²) or 2x (0.75... 2.5 mm²), and stranded conductors 2x (1... 2.5 mm²) or 2x (2.5... 6 mm²). AWG equivalents for the main contacts are 2x (14... 10). Auxiliary and control circuit terminals are also screw-type, with the same solid and stranded ranges.