What it is and what it does
The Siemens 3RV2021-1GA20-ZX95 is a SIRIUS motor protection circuit breaker — a combined disconnecting and overload protective device for three-phase induction motors. It's designed for the main current circuit of a motor branch, providing short-circuit and overload protection in one package. Rated for 100 kA breaking capacity at 400 V AC, it can safely interrupt a fault current up to that level without the upstream breaker needing to clear it — that's the SCCR (short-circuit current rating) that governs panel coordination. At 480 V AC it still holds 100 kA; at 690 V AC it's rated 4 kA. The Class 10 trip curve means it will disconnect within 10 seconds at 7.2× the thermal setting — the standard for standard-duty motor starting where the inrush doesn't linger. Phase failure detection is built in, so a lost phase on the line side won't let the motor single-phase to destruction.
Mounting and panel fit
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715. The 45 mm width and 97 mm depth fit standard motor starter assemblies. Mounting position is any. Clearance requirements: 50 mm above and below, 30 mm to the side, zero forward or backward. That's tight enough for dense panels but the 50 mm vertical gap matters for heat dissipation from the bimetal trip element.
Termination and wiring
Spring-loaded terminals on the main current circuit accept 2× (1 to 10 mm²) solid or stranded wire. No screw torque to verify — just strip and push. That saves a few minutes per termination on a multi-motor panel.
Lifecycle and sourcing
Current production — no end-of-life notice. This is the standard SIRIUS 3RV2 generation. Sourced and quoted to order against an RFQ through independent distribution.