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.
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. At 240 V the breaker handles 100 kA, so it's comfortable on 208/240 V systems with high transformer fault current.
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
The main contact terminals accept M4 screws, and the conductor cross-section accommodates 2x (0.5 to 2.5 mm²) solid or stranded. 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.