Siemens SINAMICS S120 Function Manual page 213

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Advantages of the controlled operation down to f = 0 Hz

Closed-loop operation to approx. 0 Hz (can be set using parameter p1755) and the

possibility to start or reverse at 0 Hz directly in closed-loop operation (can be set using

parameter p1750) result in the following benefits:

● No changeover operation required within closed-loop control (bumpless behavior, no

frequency dips, no discontinuities in the torque).

● Closed-loop speed control without encoder down to and including 0 Hz

● Passive loads down to a frequency of 0 Hz

● Steady-state closed-loop speed control down to approx. 0 Hz possible

● Higher dynamic performance when compared to open-loop controlled operation

If, in the closed-loop controlled mode, start from 0 Hz or reversing takes longer than 2 s, or the

time set in p1758 - then the system automatically changes over from closed-loop controlled into

open-loop controlled operation.

Operation in encoderless torque control only makes sense if, in the speed range below the

changeover speed of the motor model (p1755), the setpoint torque is greater than the load

torque. The drive must be able to follow the setpoint and the associated setpoint speed (p1499,

Passive loads

In the closed-loop controlled mode, for passive loads, induction motors can be operated under

steady-state conditions down to 0 Hz (standstill) without changing over into the open-loop

controlled mode.

Make the following settings for this:

1. Set p0500 = 2 (technological application = passive loads for encoderless control to f = 0).

2. Set p0578 = 1 (calculate technology-dependent parameters).

The following parameters are then set automatically:

– p1574 = 2 V for induction motors

– p1574 = 4 V for separately excited synchronous motors

– p1750.2 = 1, closed-loop operation down to 0 Hz for passive loads

– p1802 = 4 SVM/FLB without overcontrol

– p1803 = 106% (factory setting)

Drive functions

Function Manual, 06/2019, 6SL3097-5AB00-0BP2

6.2 Vector control without encoder (SLVC)

Vector control