Motor protection circuit breaker, 1.25 A, 100 kA — SIRIUS 3RV1021-0KA10-ZX95
The Siemens 3RV1021-0KA10-ZX95 is a SIRIUS motor protection circuit breaker rated for 1.25 A continuous current with a 100 kA breaking capacity at 400 V AC — that means it can safely interrupt a fault current up to 100 kA without welding contacts or cascading upstream, which is the full short-circuit rating you'd expect from a motor branch circuit on a 400 V distribution panel. Trip Class 10 means it will trip within 10 seconds at 7.2× rated current, fast enough to protect a standard induction motor from locked-rotor heating. It detects phase failure but not ground fault, so pair it with a separate ground-fault relay if your application requires that. The 3-pole design covers three-phase motor circuits.
Mounting and wiring — DIN rail, screw terminals, 96 mm deep
Mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 50022 — the standard DIN rail found in every industrial panel. Depth is 96 mm, width 45 mm, height 97 mm. Zero clearance needed at the back or sides, so you can pack it tight against other devices. Screw-type terminals on both main and auxiliary circuits accept solid or stranded wire: 2× (1…2.5 mm²) and 2× (2.5…6 mm²) per terminal. AWG equivalents: 2× (14…10) for the main contacts. The IP20 front protection means it's touch-safe but not washdown-rated — keep it inside the enclosure.
Electrical ratings and operating conditions
Rated insulation voltage 690 V. Breaking capacity is 100 kA across the board at 240 V, 400 V, 500 V, and 690 V AC (–) — that's consistent high-fault performance regardless of the supply voltage within that range. Maximum operating frequency in AC-3 duty is 15 operations per hour, so it's sized for motor starting duty, not high-speed cycling. Power dissipation at rated current in hot operating state is 7.25 W total, 2.4 W per pole — factor that into your enclosure thermal budget. Surge voltage resistance rated at 6 000 V. Ambient operating range -20 to +60 °C; storage and transport -50 to +80 °C. Shock resistance 25g / 11 ms. Mounting position any.