Siemens SINAMICS G120 Operating Instructions Manual page 196

Functions
5.12 Safety functions
Permissible control modes for using fail-safe functions
When the above-mentioned conditions are fulfilled, the fail-safe functions can be used for
both V/f control and vector control.
Restrictions regarding SLS and SS1
Safety functions SS1 and SLS must not be used if the motor, after it has been switched-off,
can still be accelerated by the mechanical elements of the connected machine component.
Whether or not a mechanical brake is installed is irrelevant.
Examples:
1. For the hoisting gear of a crane, the suspended load can accelerate the motor as soon as
2. A horizontal conveyor is always braked to a standstill due to friction as soon as the motor
196
CAUTION
the motor is switched-off. In this case, safety functions SS1 and SLS are not permissible.
Even if the mechanical brake of the hoisting gear is generally closed after the motor has
been switched-off, this is of no significance when it comes to the fact that SS1 and SLS
safety functions are prohibited in this application.
is switched-off. In this case, safety functions SS1 and SLS can be used without any
restriction.
CU240S and CU240E Control Units, FW 3.2
Operating Instructions, 03/2009, A5E02440075B AA