Direction Reversal Without Changing The Setpoint - Siemens SINAMICS S120 Function Manual

Basic functions

8.10 Direction reversal without changing the setpoint

8.10 Direction reversal without changing the setpoint
Function description
Excessively high torque due to an inappropriate phase sequence of the motor after direction
reversal
If a drive is synchronized to the line supply, when the direction is reversed, high torques can
be generated when connecting to the line supply if the phase sequence of the line voltage
does not match the phase sequence of the rotating motor. This high torque can destroy the
coupling between the motor and load and therefore result in death or severe injury.
● As a consequence, for this constellation, check the phase sequence of the VSM wiring and
NOTICE
Uncontrollable acceleration of the drive with an external speed actual value
When using an external speed actual value for the speed controller via p1440, positive
feedback can occur in the speed control loop. As a consequence, the drive accelerates up to
its speed limit and can be damaged.
● When using external speed actual values for the speed controller, additionally change its
Note
Position reference is lost at direction reversal
If direction reversal is configured in the data set configurations (e.g. p1821[0] = 0 and p1821[1]
= 1), when the function module "Basic positioner" or "Position control" is activated, the absolute
adjustment is reset after each data set changeover (p2507), as the position reference is lost
when the direction of rotation is switched over.
The direction of rotation of the motor can be reversed using the direction reversal via p1821
without having to change the motor rotating field by interchanging two phases at the motor and
having to invert the encoder signals using p0410. The direction reversal via p1821 can be
detected as a result of the motor direction of rotation. The speed setpoint and actual value,
torque setpoint and actual value and also the relative position change remain unchanged. The
direction change can be identified as a result of the phase voltage (r0089). When the direction
reverses, then the absolute position reference is also lost.
For vector control, in addition, the output direction of rotation of the converter can be reversed
using p1820. This means that the rotating field can be changed without having to interchange
326
WARNING
correct if necessary.
polarity when reversing the direction of rotation (p1821 = 1).
Function Manual, 06/2019, 6SL3097-5AB00-0BP2
Drive functions