Fail-safe drives are characterized by their "integrated safety functions", which they provide to the user as possible responses to safety-relevant events. The most important integrated safety functions available for Siemens drives are described in the following. The functional safety of all of the functions satisfies the requirements defined in Part 5-2 of the international standard IEC 61800 for variable-speed drive systems.

Safe stopping functions

Safe Torque Off (STO)

No wearing parts as a result of electronic shutdown. The converter remains connected to the line and can be fully diagnosed

Safe Stop 1 (SS1)

For machines where a high moment of inertia
must be quickly and safely braked

Safe Stop 2 (SS2)

The axis should be safely stopped, the position maintained and after deselection moved further without a reference point approach

Safe Operating Stop (SOS)

For applications where machine parts must be safely kept at standstill and where a holding torque is required

Safe brake management

Safe Brake Control (SBC)

For applications where a safe position must be maintained even when the motor is in a no-current condition

Safe Brake Test (SBT)

For implementing a safe brake in conjunction with SBC

Functions to safely monitor motion

Safely-Limited Speed (SLS)

For machines where a hazard can occur if a certain speed is exceeded

Safe Speed Monitor (SSM)

Allowing a machine to be entered using safe SSM feedback signal

Safe Direction (SDI)

For machines where material must be cyclically loaded or removed -
or to protect against impermissible direction of rotation

Functions to safely monitor position

Safely-Limited Position (SLP)

For machines where protection areas must be monitored

Safe Position (SP)

For machines where flexible safety functions are required