The Siemens 3RA2337-8XB30-1NB3 is a SIRIUS reversing contactor assembly — a factory-wired pair of contactors with mechanical interlock, ready to reverse a three-phase motor without external wiring of the interlock circuit. It ships with two 3RT2037-1NB30 contactors, one per direction, mechanically interlocked so both cannot close simultaneously. Rated for 30 kW at 400 V AC-3 (the standard motor-switching duty) and 65 A at 480 V, it handles motors up to 50 hp at 460/480 V and 575/600 V. The assembly is sized S2, meaning it fits the standard SIRIUS S2 footprint — 120 mm wide, 141 mm tall, 130 mm deep — and mounts via screw or snap-on onto 35 mm DIN rail.
Clearances: 10 mm upwards, forwards, downwards, and to the side; 0 mm backwards (flush to the panel). Main circuit terminals accept solid conductors: 2x 1–35 mm² or 1x 1–50 mm². Control terminals (coil) accept 2x 0.5–1.5 mm² or 2x 0.75–2.5 mm² solid or stranded. All terminals are screw-type.
The contactors are rated for 10 million mechanical operations typical. Maximum switching frequency under AC-3 duty is 700 operations per hour; the same limit applies under AC-3e. Shock resistance: 12g / 5 ms (AC) and 7g / 10 ms. Coil control voltage is 20–33 V DC. Power factor at 50 Hz is 0.36, at 60 Hz is 0.39.