What this reversing contactor assembly delivers
The 3RA9012-5AQ16 is a factory-assembled reversing contactor set — two 3-pole contactors mechanically interlocked with a 24 VDC coil, rated 18 A, and carrying 2NO-2NC auxiliary contacts built in. That means a single order code covers the reversing pair plus the aux block, saving panel space and wiring time compared to buying the contactors and interlock kit separately. The 18 A rating at 24 VDC coil voltage fits motor control applications in the fractional-to-small-horsepower range — think conveyors, hoists, or any bidirectional drive where the contactor pair must never close simultaneously. The mechanical interlock between the two contactors prevents both coils from pulling in at once, which is the failure mode that welds a reversing starter.
What the 2NO-2NC aux contacts mean in practice
The integrated auxiliary contact block gives you two normally-open and two normally-closed contacts per the description. That covers the typical feedback signals for a reversing starter: one NO per contactor for run status, one NC per contactor for interlock confirmation back to the PLC, with a spare pair left for external indication or a holding circuit. Because the aux contacts are integral to the assembly, there is no separate block to order, mount, or wire — the DIN-rail footprint stays compact, and the wiring diagram reduces to the coil terminals plus the aux terminal strip. For a panel builder, that is one less line item to manage and one less potential point of assembly error.