The Siemens 3RV2421-1AA10 is a SIRIUS circuit breaker specifically designed for transformer protection, not general motor or cable protection. Its CLASS 10 trip characteristic means it clears faults quickly enough to limit let-through energy to downstream transformers, while the 100 kA breaking capacity at 400 V AC gives it the headroom to handle high-fault utility feeds without cascading upstream. The same 100 kA rating holds at 240 V, 500 V, and 690 V — so the interrupting rating doesn't derate with voltage on this unit, which simplifies coordination studies.
Mounting and fit
Any mounting position is acceptable, so it fits in tight sub-panels or vertical bus stacks. Forwards clearance is 0 mm, so it can sit flush against a panel door or gland plate without needing an air gap.
Trip class and protection logic
Rated for transformer protection, the CLASS 10 trip ensures the breaker opens within 10 seconds at 600% of the thermal setting — fast enough to avoid saturating the transformer core during a bolted fault. No ground fault detection — that's handled separately downstream if needed.
The lifecycle stage is current, meaning Siemens still produces this order code.