Siemens SINAMICS S120, Function Manual

Page: 80 / 1094

Extended setpoint channel
3.6 Ramp-function generator
Drive functions
80
Function Manual, 11/2017, 6SL3097-4AB00-0BP5
Standard ramp-function generator tracking
If the load torque exceeds the torque limit of the drive and so causes the actual speed to
diminish, the ramp-function generator output is not tracked to the actual speed value. If the
torque limit is overshot during the ramp-up because the ramp-up time was selected too
small, the effective ramp-up time of the ramp-function generator lengthens.
Result: Once the load torque decreases, the drive accelerates again at the current limit to
the setpoint. The ramp-up is stopped when the torque, power or current limit is reached.
p1145 can be used to set the permitted following error. The speed setpoint is so tracked to
the set permitted following error. The acceleration ramp is flattened. If the torque decreases,
the ramp-up continues on the speed setpoint with a flattened ramp to the torque/current limit.
Figure 3-11 Standard ramp-function generator tracking
At the times t
1
and t
3
, an overload torque M
Ovl
starts to act on the drive in addition to the load
torque M
L
. The torque limit of the drive is exceeded.
For t
1
the drive is being ramped up along specified ramp-function generator ramp. The
additional torque prevents the further acceleration of the motor to the rated speed on the
ramp-function generator ramp.
The ramp-function generator output is tracked to the actual speed value when p1145 > 1
which causes a flattening of the rise ramp for the decrease of M
Ovl
. The drive accelerates
with flattened ramp at the current/torque limit to the speed setpoint (t
2
).
For t
3
, the drive runs with the specified speed setpoint and is already in field weakening. The
additional torque causes the drive to be braked to standstill.
For t
4
, the torque reduces again to M
L
. Because the ramp-function generator output is not
tracked to the actual speed value, the drive now accelerates at the torque/current limit to the
speed setpoint.