Description Of Functions - Siemens SINAMICS S120 Function Manual

Function modules
7.12 Master/slave function for Active Infeed
In a master/slave infeed, a common current controller cycle is essential, particularly when
infeeds 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 clock cycle for the integrated infeeds must be selected
to implement the "master/slave" function. The sampling time of the analog inputs/outputs is
to be the same as the current controller cycle (e.g. 250 µs). The slave can then use the
analog setpoint every second current controller cycle. with the dead time corresponding to
one clock 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 requirements and the necessity for one
TM31 per CU. This communication method is also more susceptible to EMC-related
problems. It is not absolutely essential to use a higher-level control (e.g. SIMATIC S7) for
this system. Control functions can also be implemented using DCC charts in individual CUs.
7.12.4

Description of functions

Description
The master/slave function module is not implemented in the higher-level control, but directly
in the firmware of the CUs and infeeds. It is signaled by r0108.19=1 (option "Master/slave"
for infeeds selected in STARTER).
The V
Module control are implemented in the function module.
All infeeds must be parameterized in such a way that they are fully functional as both a
master and slave. The infeeds can be switched between master and slave role during
operation. Switchover is handled by a higher-level control according to the setting in
parameter p3513. A master is configured to operate with V
current control, while the slaves operate only with current control (p3513=1). The
Iactive(setp) setpoint is transferred from the master to the slave via the communication links
between the CUs.
If the Active Line Module is used for reactive power compensation with external reactive
current setpoint, then the reactive current setpoint must also be wired for the slave. The
master-to-slave setpoint specifies only the active current.
When Active Line Modules have been deactivated, make sure that the maximum DC link
capacitance C
procedure (danger of overloading the pre-charging resistors).
As of firmware version V2.6, parameter p3422 (C
operation. This means that the closed-loop control can be adjusted directly via this
parameter if the master/slave configuration is changed instead of via the U
340
closed-loop control band and current setpoint via multiplexers of the Active Line
DC-link
for the remaining Active Line Modules is not exceeded during the switch-on
ZK
control (p3513 =0) and
DC-link
capacitance) can be changed during
DC link
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
controller
DC link
Drive functions