Siemens SINAMICS S120 Function Manual page 343

Explanation of the function diagram of master/slave infeeds
● Current setpoint interconnection:
● Current setpoint selection:
● Current distribution factor p3516:
● U
Drive functions
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
Parameter p3570 is used to inject the setpoint for the closed-loop current control (active
current setpoint from the master). Using parameter p3513, which can be altered in the
"ready for operation" state, it is possible to switch between master (V
parameter p3513=0) and slave (current control, parameter p3513=1) from the higher-
level control system.
The current setpoint can be selected by means of a control word (XCS) (p3572) using a
multiplexer with 4 inputs (X0 ... X3) (p3571.0 ... p3571.3). This means that the current
setpoint of the new master can be selected when the old master has failed.
The current distribution factor is calculated from the number of active infeeds and their
rated data. The sum of the current distribution factors of all active infeeds must always
equal 100%. When an infeed fails or is activated, this factor must be updated
immediately.
control band:
DC link
In master/slave operation, the Vdc limits can be violated if the load on the DC link
changes abruptly (e.g. load surges or emergency stops). For this reason, the DC link
voltage is monitored on the basis of a V
defines a specific voltage range with hysteresis in parameter p3574.0/1 (upper/lower limit
V voltage band) and p3574.2/3 (hysteresis upper/lower voltage limit). If the DC link
DC-link
voltage exits this voltage range in either direction, a signal is generated and subsequently
evaluated, causing the slave to switch over from current control to V
the DC link voltage returns to within the prescribed limits, the slave is switched back to
current control. The V
DC-link
be activated by the generated signal when necessary.
7.12 Master/slave function for Active Infeed
control band. The V
DC-link
control operates permanently in "standby mode" so that it can
Function modules
control,
DC-link
control band
DC-link
control. When
DC-link
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