SIRIUS motor protection circuit breaker, S0 frame — 3RV2021-4DA20-0BA0
The Siemens 3RV2021-4DA20-0BA0 is a SIRIUS motor protection circuit breaker in the S0 frame size, designed for protecting motor circuits against overload and short circuit. It carries a Trip Class 10 rating, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts. Breaking capacity is 25 kA at 400 VAC and 50 kA at 240 VAC, which covers most industrial panel fault levels up to that range. At 690 VAC the interrupting rating drops to 2 kA, so verify the available fault current if feeding a 690 V motor circuit. Phase failure detection is built in — the breaker will trip on loss of any phase, preventing single-phasing damage to the motor. No ground fault detection on this variant.
Mounting and integration
Mounts via screw fixing or snaps directly onto 35 mm DIN rail per DIN EN 60715. Any mounting position is permitted, so it fits tight enclosures or vertical bus bars. The S0 frame footprint is 45 mm wide × 97 mm deep × 119 mm tall — a standard panel cutout for this class. Clearance requirements: 50 mm above and below, 30 mm to the side, zero forward or backward. Keep that in mind when laying out multiple breakers in a row — the 30 mm side gap is the tightest constraint. Main circuit connections use spring-loaded terminals that accept 2× (1 to 10 mm²) solid or stranded wire. A 3 mm diameter screwdriver shaft is specified for the terminal screws.