What it is and where it lands
The Siemens 3RV2021-4BA10-ZW97 is a SIRIUS motor protection circuit breaker designed for motor protection duty. It snaps onto a 35 mm DIN rail per DIN EN 60715 and accepts screw-type terminals for the main current circuit. The 45 mm width and 97 mm depth fit standard panel layouts without crowding adjacent devices.
Key ratings and what they mean for fit
Trip Class 10 means the breaker trips within 10 seconds at 7.2× the thermal setting — the standard for standard-duty motor starting where the load doesn't hang on the acceleration curve. Phase failure detection is built in, so a lost phase on a three-phase motor will trip the breaker rather than letting the motor single-phase and burn. Breaking capacity runs 100 kA at 240 V, 25 kA at 400 V, 5 kA at 500 V, and 2 kA at 690 V — enough for most industrial distribution panels with a transformer-fed 400 V bus. The gL/gG fuse backup ratings at 400 V (63 A), 500 V (50 A), and 690 V (50 A) tell you the maximum upstream fuse that still lets the breaker clear a fault within its rated short-circuit capacity.
Panel integration notes
Mounting position is any orientation, which simplifies layout in a crowded enclosure. The 45 mm width matches the standard 45 mm grid of most DIN-rail terminal blocks and contactors, so it aligns cleanly in a row. Clearance requirements: 50 mm above and below, 30 mm to the side, 0 mm forward and backward — the forward zero means it can sit flush against a gland plate or backplane without derating. Terminal capacity accepts 2×(1…2.5 mm²) or 2×(2.5…10 mm²) solid or stranded, with M4 main contact screws.