Siemens SINAMICS S120 Function Manual page 128

Vector control
4.6 Droop
Figure 4-10 Speed controller with droop
The droop function has a torque limiting effect on a drive that is mechanically coupled to a
different speed (e.g. guide roller on a goods train). In this way, a very effective load
distribution can also be realized in connection with the torque setpoint of a leading speed-
controlled drive. In contrast to torque control or load distribution with overriding and
limitation, with the appropriate setting, such a load distribution controls even a smooth
mechanical connection or the case of slipping.
This method is only suitable to a limited extent for drives that are accelerated and braked
with significant changes in speed.
The droop feedback is used, for example, in applications in which two or more motors are
connected mechanically or operate with a common shaft and fulfill the above requirements. It
limits the torque differences that can occur as a result of the mechanical connection between
the motors by modifying the speeds of the individual motors (drive is relieved when the
torque becomes too great).
Prerequisites
● All connected drives must be operated with vector control and speed control (with or
● Only a single common ramp function generator may be used for mechanically coupled
Function diagrams (see SINAMICS S List Manual)
● 6030 Speed setpoint, droop, acceleration model
128
without an encoder).
drives.
Function Manual, (FH1), 07/2007 Edition, 6SL3097-2AB00-0BP4
Drive Functions