The Siemens SIRIUS 3RV2021-4AA15-ZW97 is a motor protection circuit breaker designed for Class 10 trip characteristics, meaning it disconnects within 10 seconds at 7.2x the thermal setting — fast enough to protect standard induction motors during locked-rotor events without nuisance tripping on normal starts. It carries a 16 A rated current at both 480 V and 600 V, and delivers a 25 kA breaking capacity at 400 V, so it can safely interrupt high-fault currents in a motor branch circuit without upstream fuses needing to clear first. Phase failure detection is built in, which is critical for three-phase motor protection: if one phase drops out, the breaker trips before the motor overheats from single-phasing. Mounting is straightforward: screw and snap-on onto 35 mm DIN rail per DIN EN 60715, in any orientation. The 45 mm width matches the standard SIRIUS compact footprint, so it fits alongside contactors in a motor starter combo without extra panel space. Clearance requirements are 50 mm above and below, 30 mm to the side, and zero forward or backward — meaning it can be mounted flush against a backplate or enclosure door.
Breaking capacity and fuse coordination
The 3RV2021-4AA15-ZW97 is rated for use with upstream gL/gG fuses up to 63 A at 400 V, 50 A at 500 V, and 40 A at 690 V. This lets the panel designer coordinate the breaker with a single set of line-side fuses across multiple motor branches — the breaker's own interrupting rating (25 kA at 400 V) covers most industrial service-entrance fault levels without requiring a current-limiting fuse ahead of it. At 240 V the breaker handles 100 kA, so it's comfortable on 208/240 V systems with high transformer fault current.
Auxiliary contact ratings
The integrated auxiliary contact is rated 1 A at 24 V, 0.5 A at 120/125/230 V, and 0.15 A at 60 V. These are the switching capacities for the built-in signal contact — useful for feeding a PLC input or a status lamp. The 1 A at 24 V DC is enough for most 24 VDC control circuits, but at 60 V the contact derates sharply to 0.15 A, so don't plan on switching a 60 VDC solenoid directly through it.
Environmental and wiring
Operating temperature range is -20 to +60 °C, storage and transport -50 to +80 °C. The main contact terminals accept M4 screws, and the conductor cross-section accommodates 2x (0.5 to 2.5 mm²) solid or stranded. The product lifecycle status is current, so this is a standard catalog item — not a phase-out or last-time-buy. For compliance documentation, the SIRIUS series carries the usual Siemens declarations (CE, UL, CSA, IEC 60947), though specific cert numbers are not in this listing.