Motor protection circuit breaker, 1.25 A, CLASS 10 — SIRIUS 3RV1021-0KA10-ZW97
The Siemens 3RV1021-0KA10-ZW97 is a SIRIUS motor protection circuit breaker rated for 1.25 A continuous current, sized for a 0.37 kW motor at 400 V AC. Its CLASS 10 trip characteristic means it disconnects within 10 seconds at 7.2× the thermal setting — fast enough to protect a standard induction motor from locked-rotor heating without nuisance tripping on normal start-up. Breaking capacity is 100 kA at 400 V AC, which covers most industrial fault levels without needing an upstream current-limiting fuse. The unit also carries 100 kA at 240 V, 500 V, and 690 V AC, so it handles high-fault panels across common voltage tiers. Phase failure detection is built in — if one line drops, the breaker trips, preventing single-phasing damage to the motor. No ground fault detection on this variant.
Mounting and wiring — DIN rail, 45 mm wide, screw terminals
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The 45 mm width fits a standard 9 mm pitch panel layout — five modules wide. Depth is 96 mm, height 97 mm, leaving clearance for adjacent devices and wire bends. No side or backward clearance required. Main circuit terminals accept solid or stranded conductors: 2× (1…2.5 mm²) and 2× (2.5…6 mm²), or AWG 14–10. Screw-type terminals — torque to the manufacturer's spec for reliable connection. No auxiliary contacts included (0 supplied), but an auxiliary switch can be added externally. Rated surge voltage resistance is 6 kV, and the enclosure is IP20 on the front — protected against finger contact but not washdown. Install inside a panel or enclosure rated for the environment.
Environmental and mechanical limits
Operating temperature range is -20 to +60 °C; storage and transport range is -50 to +80 °C. Maximum operating altitude is 2,000 m. Shock resistance is 25 g for 11 ms — suitable for machine-mounted applications with moderate vibration. Mounting position is any orientation, which simplifies panel layout. Mechanical endurance of the main contacts is typically 100,000 operations. Maximum switching rate at AC-3 duty is 15 operations per hour.