SERCOS II Bus Coupler BK7520
Power LEDs
Bus Coupler
Input for
power contacts
Power contacts
Fieldbus signal input
Fieldbus signal output
Configuration interface
Baud rate
Transmit intensity
Address selector

BK7520 | SERCOS II Bus Coupler

SERCOSThe BK7520 Bus Coupler connects the SERCOS bus system with the electronic terminal blocks, which can be extended in modular fashion. One unit consists of one Bus Coupler, any number from 1 to 64 terminals and one end terminal. The BK7520 allows, with the K-bus extension technology, the connection of up to 255 Bus Terminals to one Bus Coupler. The Bus Coupler recognizes the connected terminals and automatically generates the affiliations of the inputs/outputs to the bytes of the process image.

SERCOS is a fiber optic bus that was developed for use in drive technology as a digital drive interface for drives. SERCOS is an open fieldbus system, which since 1995 has been subject to the international standard IEC 61491 for numerically controlled machines. It is widely used in the drive technology sector.

The bus consists of a master and of a number of slaves. In SERCOS, most of the slaves are drive amplifiers. The bus topology is a ring system, in which it is possible to operate up to 254 stations. The transmission speed is 2 and 4 Mbaud. The BK7520 supports additionally 8 and 16 Mbaud. There are basically three types of telegrams. The master SYNC telegram is received by all the slaves at the same time, and is used for synchronization. The master data telegram is also received by all the slaves, and contains the cyclic data and the service data. The slaves send their data in what is known as a drive telegram.

Parameterization can also be carried out via the SERCOS interface.

System data BK7520
Number of I/O stations 254
Number of I/O points depending on controller
Data transfer medium 1,000 µm plastic fibre optic
Distance between stations 40 m plastic fibre optic
Data transfer rates 2/4/8/16 Mbaud
Technical data BK7520
Number of Bus Terminals 64 (255 with K-bus extension)
Max. number of bytes fieldbus 254 word I/O for the cyclic interface (depending on the master)
Digital peripheral signals 1,020 inputs/outputs
Analog peripheral signals 254 inputs/outputs
Configuration possibility via KS2000
Data transfer rates 2/4/8/16 Mbaud, adjustable by means of configuration switch
Bus interface FSMA standard, IEC 872-2
Power supply 24 V DC (-15 %/+20 %)
Input current 70 mA + (total K-bus current)/4, 500 mA max.
Starting current 2.5 x continuous current
Recommended fuse ≤ 10 A
Current supply K-bus 1750 mA
Power contacts max. 24 V DC/max. 10 A
Electrical isolation 500 V (power contact/supply voltage/fieldbus)
Weight approx. 170 g
Operating/storage temperature 0…+55 °C/-25…+85 °C
Relative humidity 95 %, no condensation
Vibration/shock resistance conforms to EN 60068-2-6/EN 60068-2-27
EMC immunity/emission conforms to EN 61000-6-2/EN 61000-6-4
Protect. class/installation pos. IP 20/variable
Approvals/markings CE, UL, ATEX
Ex marking II 3 G Ex nA IIC T4 Gc
Accessories/related products  
KS2000 configuration software for extended parameterisation
Cordsets cordsets and connectors
BK7500 SERCOS interface Bus Coupler for up to 64 Bus Terminals
SERCOS For further SERCOS products please see the system overview