What it is and what it does
The Siemens 3RV6021-4FA15 is a SIRIUS motor protection circuit breaker, size S0, designed to protect three-phase motor circuits against overload and short circuit. It combines a thermal overload release (CLASS 10 trip curve) with a magnetic short-circuit trip in a single 3-pole device rated 40 A at 690 V. CLASS 10 means the overload relay trips within 10 seconds at 7.2× the current setting — fast enough to protect standard induction motors during a locked-rotor condition without nuisance tripping on normal starting inrush.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, in any orientation. The S0 frame size (45 mm wide, 97 mm tall, 96 mm deep) fits standard motor control center buckets and small panel enclosures. Clearance requirements: 70 mm above and below, 30 mm to the sides, zero forward or backward. Screw-type terminals on both main and auxiliary circuits accept 2×(0.5…1.5 mm²) or 2×(0.75…2.5 mm²) solid/stranded, or AWG equivalents. Main contact torque spec: 2…2.5 N·m.
Electrical and environmental ratings
Rated operational current 40 A at AC-3 duty (motor switching), with a maximum operating frequency of 15 operations per hour at that load. Rated insulation voltage 690 V, surge voltage resistance 6 kV. Power dissipation 14 W typical. Operating temperature range -20 to +40 °C, storage/transport -50 to +80 °C. Relative humidity 10…95 %. Shock rated at 25 g / 11 ms per IEC 60068-2-27.