Safe Stop 1 (Ss1); Safe Stop 2 (Ss2) - Siemens SIMATIC S7-1500 Function Manual

Basics
3.11 Safety functions in the drive
3.11.3

Safe Stop 1 (SS1)

The Safe Stop 1 (SS1) safety function brings a drive to standstill quickly and safely via a
drive-internal rapid stop ramp. Safe Torque Off (STO) is activated after standstill. STO
ensures that no torque generating energy acts on a drive. This prevents an unintended
startup of the controller.
You can use the SS1 safety function when a fast stop of the drive with a subsequent
transition to STO is required. SS1 is used, for example, to quickly stop high inertia or brake
drives quickly and safely at high speeds
Behavior with S7-1500 Motion Control
When SS1 is triggered, the drive decelerates at a drive-internal rapid stop ramp and
automatically triggers the Safe Torque Off (STO) safety function.
When SS1 is triggered in the drive, the technology alarm 550 (alarm reaction: Follow-up
setpoint) is output and the actual values supplied by the drive are automatically tracked as
setpoints. The actual values are not monitored at the controller end. When standstill is
achieved, technology alarm 421 is output, and the technology object is disabled (alarm
reaction: Remove enable).
When the SS1 signal is no longer present in the drive, you can enable the technology object
again after the acknowledgment of the alarm.
3.11.4

Safe Stop 2 (SS2)

The Safe Stop 2 (SS2) safety function brings a drive to standstill quickly and safely via a
drive-internal rapid stop ramp. When standstill is achieved, the standstill position is
monitored at the drive end. The drive can deliver full torque to maintain the standstill.
SS2, for example, is used for machine tools.
Behavior with S7-1500 Motion Control
When SS2 is triggered, the drive decelerates at a drive-internal rapid stop ramp. The drive
control monitors the standstill.
When SS2 is triggered in the drive, the technology alarm 550 (alarm reaction: Follow-up
setpoint) is output and the actual values supplied by the drive are automatically tracked as
setpoints. The actual values are not monitored at the controller end.
When the SS2 signal is no longer present in the drive, the drive goes automatically into "read
for operation" mode. The operational readiness of the drive is indicated in the technology
object tags <TO>.StatusDrive.InOperation with TRUE. The technology object is
automatically enabled again after acknowledging the alarm.
34
S7-1500 Motion Control V13 Update 3
Function Manual, 07/2014, A5E03879256-AC