Motor protection circuit breaker for 5 A loads
The Siemens SIRIUS 3RV1021-1FA15 is a motor protection circuit breaker rated for a continuous current of 5 A, designed to protect induction motors up to 1.5 kW at 400 V AC. Its CLASS 10 trip class means it will trip within 10 seconds at 7.2× rated current — fast enough to protect standard squirrel-cage motors during a stall or locked-rotor event without nuisance tripping on normal starting inrush. Phase failure detection is built in, so a lost phase on the line side will trip the breaker and prevent single-phasing damage to the motor. The breaker mounts on 35 mm DIN rail per DIN EN 50022 using either the integrated snap-on clips or screws through the mounting base. Zero clearance is required at the sides and rear (0 mm backwards, 0 mm at the side), so it can be packed tightly against other devices in a panel without derating — useful when filling a high-density motor control centre row.
Breaking capacity and selectivity
The 3RV1021-1FA15 delivers 100 kA breaking capacity at 240 V, 400 V, and 500 V AC — sufficient for most industrial installations with high fault current potential. At 690 V AC the breaking capacity drops to 6 kA, so in 690 V systems it must be coordinated with an upstream backup fuse or circuit breaker that limits let-through energy. The rated insulation voltage is 690 V, and the surge voltage resistance is 6 000 V, confirming suitability for 400/480 V panels with margin.
Auxiliary contacts and control wiring
The breaker accepts a factory-fitted or field-installable auxiliary switch (transverse design) that extends the product's functionality for remote status indication. The auxiliary contact ratings are 1 A at 24 V, 0.5 A at 230 V, and 0.15 A at 60 V — these are the maximum switching currents for the auxiliary circuit, not the main motor circuit. Screw terminals are used for both the main power circuit and the auxiliary/control circuit. Solid wire sizes accepted are 2× (0.5 to 1.5 mm²) and 2× (0.75 to 2.5 mm²); stranded wire sizes are 2× (1 to 2.5 mm²) and 2× (2.5 to 6 mm²).