BK3150 by Beckhoff

The BK3150 is a bus coupler produced by Beckhoff for the BK PROFIBUS Bus Couplers series. Acting as the interface between a PROFIBUS trunk line and a stack of Beckhoff I/O terminals, the unit converts real-time fieldbus telegrams into locally buffered process data so controllers can access mixed signal blocks over a single network link. Within an automation cell, it is installed on a DIN rail beside power supplies and terminal slices, enabling distributed measurement and actuation without requiring separate communication modules.

Communication on the PROFIBUS side is based on RS-485 signaling and reaches a throughput of 12 Mbaud, while telegrams pass through a 9-pin D-sub connector that carries data and provides a shield connection to the cabinet ground. Internally, the coupler can map up to 256 digital inputs and outputs and an additional 128 analog inputs and outputs. These channels are condensed into a memory image that does not exceed 128 bytes, helping maintain predictable PLC task times. The housing measures 44 mm in width, 100 mm in height, and 68 mm in depth, allowing tight side-by-side mounting without exceeding the profile of adjacent terminal blocks.

Field power enters through the left-side contacts with a rated supply of 24 V DC, and the same rail passes power to downstream terminals. During startup, power consumption can momentarily rise to 2.5 times the steady-state draw, so the supply must accommodate the initial surge. Under continuous operation, the electronics draw no more than 320 mA, while the power contacts can carry up to 10 A for connected loads. Functional insulation has a dielectric strength of 500 V, providing electrical separation between the relevant circuits. The enclosure has an IP20 protection rating, which guards against contact with hazardous internal parts and makes the unit suitable for installation inside a closed control cabinet.