What it is and what it does
The Siemens SIRIUS 3RV1011-0KA10-ZW96 is a motor protection circuit breaker designed to protect three-phase motors against overload and short-circuit. It sits between the contactor and the supply in a motor starter assembly, combining the overload relay and short-circuit protection in one device. The Class 10 trip characteristic means it will disconnect within 10 seconds at 7.2× the thermal setting current — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starting current.
Interrupting capacity — the real-world breaker
This breaker carries a 100 kA interrupting capacity at 240 V, 400 V, and 500 V — that is the fault current it can safely clear without welding contacts or rupturing the case. At 690 V the rating drops to 2 kA, so verify the available fault current at the point of installation if your line runs at 690 V. The high SCCR at the common 400 V industrial level means it can be used downstream of a transformer without needing a current-limiting fuse in most panels.
Phase failure detection — why it matters
Phase failure detection is built in. If one supply phase drops out, the breaker trips — preventing single-phasing, which draws high current in the remaining windings and burns a motor fast. This is a standard feature on SIRIUS motor-protective breakers, not an option card.
Mounting and panel fit
Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715. The 45 mm width (three module spaces) and 75 mm depth leave room for adjacent contactors and terminals. Any mounting position is allowed. The screw-type terminals for the main circuit accept 2×(0.5…1.5 mm²) or 2×(0.75…2.5 mm²) solid or stranded — common for motor feeds up to the rated current. Clearance: 20 mm above and below, 9 mm to the side, zero forward and backward.