Transformer-protection circuit breaker, 1.25 A, Class 10 — SIRIUS 3RV6411-0KA10
The Siemens 3RV6411-0KA10 is a SIRIUS circuit breaker designed specifically for transformer protection, with a rated operational current of 1.25 A at 400 V AC-3 duty and a thermal-magnetic release (Class 10 overload, magnetic short-circuit trip). Rated for 690 V AC-3 maximum, 50/60 Hz, and 3-pole switching, it handles the inrush characteristic of small transformers without nuisance tripping — the Class 10 curve allows a brief overload window before the thermal element opens. Mounts on 35 mm DIN rail per DIN EN 60715 via screw and snap-on fastening, in any orientation, with 50 mm clearance above and below and 30 mm at the sides for heat dissipation and wiring access.
Sizing and coordination for transformer primary protection
At 1.25 A and Class 10, this breaker is sized for the primary side of control transformers or small power transformers where the inrush peak can exceed the full-load current for a few seconds. The magnetic short-circuit trip clears a hard fault fast, while the thermal element rides through the magnetizing inrush. The 6 W total power loss at rated current is low enough that multiple units can be ganged on a DIN rail without forced cooling, provided the 30 mm side clearance is respected. Compared to the general-purpose 3RV6011-0CA10 (same frame size S00, same 1.25 A rating but Class 10A), the 3RV6411-0KA10's Class 10 curve is slightly slower on overload — a deliberate choice for transformer primary duty where the load is a magnetic circuit, not a motor.
Lifecycle and compliance — active, RoHS-compliant
RoHS compliance date is 05/01/2012, confirming the part meets the EU RoHS substance restrictions effective from that date. REACH and WEEE compliance are standard for the SIRIUS series.
Panel integration — DIN rail, screw terminals, clearances
Snap-on mounting onto 35 mm DIN rail (DIN EN 60715) with screw fastening for vibration resistance. The 45 mm width (3-module) fits standard enclosure cutouts. Screw-type terminals on top and bottom accept 2x (0.75–2.5 mm²) solid/stranded or 2x 4 mm², or AWG 18–12 / 20–16. Tightening torque: 0.8–1.2 N·m. Depth 96 mm, height 97 mm — fits standard 100 mm deep enclosures. Clearances: 50 mm above/below, 30 mm sides, 0 mm forward/backward (no extra space needed beyond the device envelope). Operating temperature -20 to +60 °C, storage -50 to +80 °C, relative humidity 10–95%. Shock rated 25g / 11 ms per IEC 60068-2-27. Installation altitude up to 2000 m.