Product Description:

The BK3120 EtherCAT bus coupler is produced by Beckhoff within the BK EtherCAT Bus Couplers series. It links discrete Beckhoff I/O terminals to an EtherCAT network while forwarding field supply voltage and process data to the attached slices. In automated machinery, the unit serves as the interface between the controller and decentralized sensors or actuators, translating the high-speed serial protocol into the local K-bus format used by the terminal stack.

This coupler supports a line baud rate of 12 Mbaud, matching the EtherCAT physical layer so cyclic data can be exchanged with minimal latency. The fieldbus is accessed through one 9-pin D-sub plug, which simplifies panel layouts because no additional communication sockets are required. Internal electronics are energized from a control cabinet feed of 24 V DC, and under standard loading the unit draws up to 500 mA on that supply rail. To back-feed attached terminal modules, the device sources a K-bus current of 1750 mA, allowing dense assemblies to be powered without auxiliary wiring. Process images up to 128 bytes are exchanged each cycle, providing enough bandwidth for mixed analog and digital channel blocks.

For installations that scale beyond a small I/O island, the head station can address up to 255 downstream terminals while also providing a separate local limit of 64 mechanically linked slices. The power contacts are dimensioned for continuous loads of 10 A at 24 V DC, so high-current actuators can share the same backplane conductors used by sensors. An enclosure rating of IP20 indicates finger protection but requires mounting inside a closed control cabinet. It also has 500 V dielectric strength between the supply and electronics, supports 64 analog or 1020 digital signal points, and recommends a 10 A fuse on the 24 V feed.