The Siemens SIRIUS 3RV1021-1FA10-ZW95 is a 3-pole motor protection circuit breaker rated for 5 A continuous current with a Class 10 trip characteristic. It breaks up to 100 kA at 400 V AC, which means it can safely clear a bolted fault on a 400 V line without the upstream breaker needing to trip — that's full selectivity for a motor branch circuit. Phase failure detection is built in, so a single-phased motor won't cook before the overload trips.
Mounting and integration
Snaps onto a 35 mm DIN rail per EN 50022. Screw-type terminals on the main circuit accept 2x (1 to 2.5 mm²) solid or stranded, or 2x (2.5 to 6 mm²) — the same range for both, so no derating when switching between fine-stranded with ferrules and solid. Zero clearance needed at the sides or back; the 45 mm wide footprint leaves room for a contactor alongside in a standard motor starter stack.
What the ratings mean for fit
The 5 A continuous rating at 690 V maximum sets the motor FLA it can protect — size it to the motor nameplate, not the breaker's maximum. The 100 kA breaking capacity at 400 V AC is the interrupting rating; it's high enough for most industrial service-entrance panels without a current-limiting fuse ahead. Trip Class 10 means it will trip within 10 seconds at 7.2× the thermal setting, which keeps the motor winding safe during a stall or jam. The 100,000-cycle mechanical endurance is the rated life of the main contacts under normal switching — expect fewer cycles if it's used as a disconnect under load regularly.