The Siemens 3RV1021-4BA10-ZW95 is a SIRUS motor protection circuit breaker designed for motor protection in control panels. It combines a circuit breaker and overload relay in one device, providing short-circuit and overload protection for motor circuits. Rated at 20 A continuous current with a CLASS 10 trip class, it's sized for motor loads up to 7.5 kW at 400 V AC-3 duty. That's the figure that governs selectivity coordination in the panel. That prevents single-phasing damage on a three-phase motor.
Any mounting position allowed. Screw-type terminals on the main circuit accept solid or stranded wire: 2x (1 to 2.5 mm²) or 2x (2.5 to 6 mm²), with matching AWG 14 to 10 for the main contacts. The auxiliary switch terminal takes the same range.
Rated for installation altitudes up to 2,000 m without derating. Shock resistance 25g for 11 ms. Power dissipation at rated current is 10.5 W total (3.5 W per pole) in hot operating state. That matters for thermal management inside a sealed enclosure.