Product identity and motor protection rating
The Siemens 3RV1021-0KA15-ZW98 is a SIRIUS motor protection circuit breaker designed for motor protection duty. It carries a continuous current rating of 1.25 A and a rated motor power of 0.37 kW at 400 V AC, making it suited for small induction motors — fractional-horsepower pumps, fans, or conveyor drives in a control panel. Trip class is CLASS 10, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect a standard squirrel-cage motor during a locked-rotor event without nuisance tripping on normal starts. Phase failure detection is built in, so a single-phase condition on a three-phase motor will trigger a trip — a critical feature for preventing single-phasing damage on delta-connected loads.
Breaking capacity and fault interruption
This breaker delivers 100 kA breaking capacity at 240 V, 400 V, 500 V, and 690 V AC (–). That is a high-fault rating for a 1.25 A device — it can interrupt a bolted fault up to 100 kA without welding contacts or cascading failure upstream. In a panel with a high-available-fault transformer, this lets you avoid a larger upstream breaker. Rated insulation voltage is 690 V, and the maximum operating voltage for AC-3 motor switching is also 690 V. The auxiliary switch contacts are rated 1 A at 24 V, 0.5 A at 230 V, and 0.15 A at 60 V — enough for a PLC digital input or a status lamp.
Mounting and integration
Mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 50022. The 45 mm width and 97 mm height fit a standard 45 mm-wide DIN-rail slot — one module wide. Depth is 96 mm, so it clears a 100 mm-deep enclosure. IP20 on the front means finger-safe but not washdown; keep it inside a closed panel. Terminals are screw-type for the main current circuit. Solid wire sizes accepted: 2× (0.5–1.5 mm²) and 2× (0.75–2.5 mm²); stranded: 2× (1–2.5 mm²) and 2× (2.5–6 mm²). No special ferrules needed, but the 2.5 mm² upper end on stranded matches standard motor leads up to 2.5 mm². Mounting position is any, and zero clearance is required at the sides or rear — you can pack breakers side-by-side without derating for heat buildup.
Environmental and lifecycle
Operating temperature -20 to +60 °C; storage and transport -50 to +80 °C. Shock resistance 25 g for 11 ms. Maximum altitude 2,000 m.