Ss2 (Extended Functions) - Siemens SINAMICS S120 Commissioning Manual

4.10.4.5

SS2 (extended functions)

The "Safe Stop 2" ("SS2") function is used to brake the motor safely along the OFF3
deceleration ramp (p1135) with subsequent transition to the "SOS" state (see Chapter "Safe
Operating Stop (SOS) (Page 239)") after the delay time expires (p9552). The delay time set
must allow the drive to brake to a standstill from every speed of the operating process within
this time. The standstill tolerance (p9530) may not be violated after this time. After braking,
the drives remain in speed control mode with the speed setpoint n = 0. The full torque is
available. The default setpoint (e.g. from the setpoint channel, or from a higher-level
controller) remains inhibited as long as "SS2" is selected.
Note
Interruption of the ramp function with OFF3
Activating SS2 can mean that the higher-level controller (PLC, motion controller) which
specifies the speed setpoint, interrupts the ramp function (e.g. with OFF2). The device
behaves in this way as a result of a fault response triggered by OFF3 activation. This fault
response must be avoided by assigning appropriate parameters or configurations.
Differences between "Safe Stop 2 with OFF3" and "SS2 with external stop (SS2E)"
The following differences exist:
● If SS2 with external stop is selected, the drive does not brake the motor autonomously
but follows the defined speed setpoint.
● During the delay time p9553, the brake ramp (SBR) and the acceleration (SAM) are not
monitored and there is no standstill detection.
● SOS becomes active after the delay time p9553 has expired.
If the SS2E function is active, the higher-level controller must define the speed setpoint
such that the motor is stopped no later than after the delay time p9553 has expired.
● To enable "Safe Stop 2 with external stop", set the "SS2E enable" switch to "Connection".
● The PROFIsafe control word S_STW2.28 selects the SS2E function. PROFIsafe
S_STW2.28 is contained in telegrams 31, 901, 902, and 903.
● The PROFIsafe status word S_ZSW2.28 indicates whether the SS2E function is active.
The PROFIsafe status word S_ZSW2.28 is contained in telegrams 31, 901, 902, and 903.
The associated diagnostics parameter is r9722.28.
In the "Safety Info Channel," status word S_ZSW3B.11 indicates whether the SS2E
function is active. The associated diagnostic parameter is r10234.11.
The diagnostic parameters p9722.28 and p10234.11 are also set during an internal
STOP D.
Commissioning with Startdrive
Commissioning Manual, 11/2017, 6SL3097-4AA10-0BP1
Commissioning
4.10 Safety Integrated commissioning
241