Types Of Communication - Siemens SINAMICS S120 Function Manual

Function modules
9.9 Master/slave function for Active Infeed
Shutting down an ALM from an operating group
Shutting down an ALM from the group should be realized in the slave state and with OFF2
(pulse inhibit). If a master fails with a fault (OFF2 response, pulse inhibit), one of the slaves
must be immediately switched as master.
Restrictions
● Two masters must not be operated simultaneously in the infeed group.
9.9.3

Types of communication

Description
To implement Master/Slave operation, the CUs must be able to communicate with one another.
The master passes the active current setpoint to the slaves. To optimize V
voltage), the dead times during communication must be kept to a minimum.
PROFIBUS slave-to-slave communication
The data is exchanged directly between the CUs without passing via the DP master. A higher-
level controller (e.g., SIMATIC S7) as the PROFIBUS master is needed as "clock generator" for
this. The minimum PROFIBUS cycle time that can be set depends on the PROFIBUS master
specifications.
Isochronous mode must be set for PROFIBUS. The PROFIBUS cycle time must not exceed 2
ms otherwise the closed-loop control may start to oscillate.
In order to ensure that other infeed units do not switch to fault status when one CU fails, the fault
message F01946 "Link to Publisher disconnected" must be deactivated.
The number "1946" can be set in one of the parameters p2101[0..19] and p2101[x] set to "0" in
order to block fault message F01946. This means that the drive will not shut down when one
slave-to-slave communication node fails.
In a Master/Slave infeed unit, a common current controller cycle is essential, particularly when
infeed units with different outputs are used. If the number of PROFIBUS nodes or drives
increases, this can affect the bus cycle or current controller sampling time.
Communication using an analog setpoint
The analog setpoint between the CUs with Terminal Module 31 (TM31) can also be used as an
alternative to bus communication. The factory setting for the sampling time of analog inputs
and/or outputs is 4 ms (TM31 inputs/outputs sampling time p4099[1/2]). The sampling times
must be an integer multiple of the basic sampling times (r0110). The lowest common
denominator of the current controller cycle for the integrated infeed units must be selected to
implement the "Master/Slave" function. The sampling time of the analog inputs/outputs should
be the set to the same value as the current controller cycle (e.g. 250 µs). The slave can then use
the analog setpoint every second current controller cycle. The dead time is then one cycle.
The advantages of this variant is that the communication system can be configured to be
independent of bus and master.
Disadvantages are the additional hardware wiring and the necessity to use one TM31 per CU.
This communication method is also more susceptible to EMC-related problems. It is not
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dc
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
control (DC-link
Drive functions