The Siemens 3RA2337-8XB30-1KB4 is a SIRIUS reversing contactor assembly — a factory-wired pair of contactors with mechanical interlock, sized S2, that reverses a three-phase motor by swapping two phases. It ships with two 3RT2037-1KB40 contactors already mounted and interlocked, saving panel-build time over ordering and assembling the pair separately. Rated 30 kW at 400 V AC-3 (the standard motor-switching duty class per IEC 60947-4-1), it handles reversing loads up to that power. At 480 V the thermal current rating is 65 A, and at 690 V it still carries 37 kW — useful for 690 V distribution in mining or marine plants. The coil is 24 V DC, screw-type terminals on both the magnet coil and the main power circuit. The S2 frame keeps the footprint compact: 120 mm wide, 141 mm tall, 130 mm deep — fits a standard 600 mm enclosure depth with room for wiring.
Mounting and clearances — what the panel builder needs
That covers most panel layouts where the contactor needs to sit at an angle for wire routing. Clearance to adjacent components: 10 mm upwards, forwards, downwards, and to the side — zero mm backwards (the back is flush to the DIN rail). That 10 mm gap is the minimum for heat dissipation at full rated current; tighter spacing forces derating. Wire sizes: the main power circuit accepts solid conductors from 1 mm² up to 35 mm² (two per terminal) or one up to 50 mm². Screw terminals throughout — no spring-cage on this variant.