Speed Controller - Siemens SINAMICS S120 Function Manual

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Operating Modes
Vector control
3.2.3

Speed controller

Both closed-loop control procedures with and without an encoder (VC, SLVC) have
the same speed controller structure, which contains the following components:
S PI controller
S Speed controller pre-control
S Droop function
The total of the output variables result in the torque setpoint, which is reduced to
the permissible magnitude by means of the torque setpoint limitation.
Speed controller
The speed controller receives its setpoint (r0062) from the setpoint channel and its
actual value (r0063) either directly from the speed sensor (control with sensor
(VC)) or indirectly via the motor model (control without sensor (SLVC)). The sy-
stem deviation is increased by the PI controller and, in conjunction with the pre-
control, results in the torque setpoint.
When the load torque increases, the speed setpoint is reduced proportionately
when the droop function is active, which means that the single drive within a group
(two or more mechanically connected motors) is relieved when the torque beco-
mes too great.
Closed-loop
speed control
r
0062
r
1084
Speed Setpoint
r
0063
Actual speed
*)
Only active if pre-control is active
(p1496 > 0)
Fig. 3-28
Speed controller
The optimum speed controller setting can be determined via the automatic speed
controller optimization function (p1900 = 1, rotating measurement) (see also:
Subsection 3.2.11).
3-126
Droop
injection
Pre-control
K
T
p
n
*)
PI speed
controller
T
i
r
1508
r
1482
r
1538
r
[0]
1547
r
[1]
1547
r
1539
T
K
i
p
p
p
SLVC:
1452
1470
p
p
VC:
1442
1460
© Siemens AG 2006 All Rights Reserved
SINAMICS S120 Function Manual, 03/2006 Edition
r
0079
Torque
setpoint
T
n
p
1472
p
1462

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