Siemens SINAMICS GL150

8.3.5 Ramp-function generator
The ramp-function generator limits the rate at which the setpoint changes when the drive is
accelerating or decelerating. This prevents excessive setpoint step changes from damaging
the drive train. Two ramp function generators are available; these can be selected using
parameters.
To improve the control properties with regard to load surges, set additional rounding times in
the lower and upper speed range.
Setting rounding times has the following advantages:
● It protects mechanical components, such as shafts and couplings.
● It prevents the actual speed value from being overshot when the setpoint is approached,
thereby improving control quality.
The ramp-up and ramp-down times each refer to the maximum speed.
Note
If rounding times are too long, this can cause the setpoint to be overshot if the setpoint is
reduced abruptly during ramp-up.
Rounding is also effective in the zero crossover; When the direction of rotation is reversed, the
ramp-function generator output is reduced to zero via the initial rounding, the ramp-down time
and the final rounding. Then, the newly inverted setpoint will be approached via the initial
rounding, the ramp-up time and the final rounding.
Rounding times that can be set separately are active in the event of a fast stop (OFF3). The
actual ramp-up/ramp-down times increase with active rounding.
8.3.6 Vector control
Vector control has the following advantages:
● Stability vis-à-vis load and setpoint changes
● Short rise times for setpoint changes to facilitate an improved control response
● Short settling times for load changes to facilitate an improved response to disturbances
● Acceleration and braking are possible with the maximum available torque.
● Motor protection due to variable torque limitation in motor and regenerative mode
● Drive and braking torque controlled independently of the speed
These benefits can even be achieved without speed feedback.
You can use vector control with or without an encoder. A speed encoder is only required in the
following cases:
● Maximum speed accuracy is required.
● The most stringent demands on the dynamic response are required.
● Better command behavior is desired.
Operation
8.3 Setpoint channel and closed-loop control
SINAMICS GL150 6SL38555UN113KA0Z
Operating Instructions Rev.201910281450 EXAMPLE 111