Siemens SINAMICS S120 Function Manual page 301

In the following cases, when a DDS switch takes place, the current actual position value
becomes invalid (p2521 = 0) and the reference point (r2684.11 = 0) is reset.
● The EDS that is effective for the position control changes.
● The encoder assignment changes (p2502).
● The mechanical relationships change (p2503...p2506)
With absolute encoders, the status of the adjustment (p2507) is also reset, if the same
absolute encoder is selected for the position control although the mechanical relationships
have changed (p2503 ... p2506).
In operating mode, a fault message (F07494) is also generated.
The following table contains a few examples for data set switching. The initial data set is
always DDS0.
Table 7- 6 DDS switchover without load gear position tracking
DDS p186 p187
(MDS) (encoder_1)
0 0 EDS0
1 0 EDS0
2 0 EDS0
Drive functions
Function Manual, (FH1), 10/2008, 6SL3097-2AB00-0BP5
p188 p189
(encoder_2) (encoder_3)
EDS1 EDS2
EDS1 EDS2
EDS1 EDS2
Encoder Mechanic Load gear
for al position
position condition tracking
control s
p2502 p2504/
p2505/
p2506 or
p2503
encoder_ xxx disabled
1
encoder_ xxx disabled
1
encoder_ yyy disabled
1
Function modules
7.9 Basic positioner
Switchover response
---
Switchover during pulse
inhibit or operation has no
effect
Pulse inhibit: Position
actual value conditioning is
newly initiated and
1)
reference bit is reset.
2)
Operation:
Fault message is
generated. Position actual
value conditioning is newly
initiated and reference bit
1)
is reset.
2)
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