SINAMICS S120 Safety Integrated

SINAMICS S120  Safety

Within the SINAMICS drive family, SINAMICS S120 is the drive system for motion control applications.
It has an extensive safety package that helps to protect personnel as well as machines. This safety package is extremely efficient and cost effective as the safety functions are completely integrated into the drive system. Not only this, your machine can be safely and practically operated under all of the relevant operating conditions. For instance, in the setting-up and test modes with the protective door open. The safety functions comply with the requirements laid down in DIN EN 61508 for use up to and including SIL 2 (Safety Integrity Level), Category 3 and PL d (Performance Level) according to DIN EN ISO 13849. As a consequence, the essential requirements relating to functional safety can be simply and cost-effectively implemented.

Included in the function scope are the following, e.g.:

  • Functions for safe stopping

  • Functions for safely monitoring motion

  • Functions for safely monitoring position

  • Functions for safe brake management

Product features

  • Functions to protect personnel and machines

  • Short response times as it is integrated in the drive system

  • Can be used in all operating modes

  • Replaces external electromechanical devices


The safety functions are available in all operating modes and can communicate with the process via safety-relevant input/output signals.
Communication via fieldbus (PROFINET or PROFIBUS) with the safety-related PROFIsafe profile is already possible in the standard version.

The safety functions are commissioned using STARTER.
The partially automated acceptance test for all safety-related functions can be performed with support from STARTER.

SINAMICS S120 has the following safety functions integrated in the drive:

Short description


STO - Safe Torque Off

The torque is safely shut down and prevents an inadvertent restart.
Electronic shutdown, therefore no wearing parts. The drive remains connected to the line supply and can still be fully diagnosed.

SS1 - Safe Stop 1
SS2 - Safe Stop 2

When a monitoring function or a sensor responds (e.g. light barrier) this function safely brings drives to a standstill (zero speed).
SS1 is also suitable for machines with high moments of inertia that must be safely and quickly braked.
Using SS2, for example, an axis can be safely stopped, the standstill position held and when deselected, can continue to be traversed without requiring a reference point approach.

SOS - Safe Operating Stop

Monitors the drives for standstill. The drives remain completely functional in closed-loop position control.
For instance, SOS is suitable for applications where machine parts must be kept safely at standstill, and a holding torque is required.

SBC - Safe Brake Control

A holding brake is controlled through two channels
Suitable for applications where a safe position must be held, even when the motor is in a no-current condition.

SBT - Safe Brake Test

Cyclic test of brakes subject to wear
Suitable to implement a safety-related brake together with SBC.

SLS - Safety Limited Speed

Monitors configurable speed limit values, for example, when setting-up without an agreement button.
SLS is suitable for machines where hazards can occur if a speed is exceeded, for example.

SSM - Safe Speed Monitor

Supplies a safety output signal if the drive speed lies below a configurable limit value.
For instance, using SSM, access to the machine can be enabled using the safety-related feedback signal.

SDI - Safe Direction

Safely monitors whether the permissible motion direction is exited. If this is the case, a parameterizable stop function is activated, e.g. STO.
For instance, SDI is suitable for machines where material must be loaded or removed cyclically.

SLP - Safely Limited Position

This function safely monitors whether a permissible traversing range is exceeded. If this is the case, a programmable stop function is activated, e.g. STO (Safe Torque Off).
SLP is suitable for machines, where protective areas must be monitored, for example. Safety-related software limit switches can be implemented using SLP; this means that mechanical limit switches can be eliminated.

SP - Safe Position

Safe transfer of position actual values of a drive via PROFIsafe for further processing in an F control
SP is suitable for machines where flexible safety functions are required, for instance.

Customer benefits

  • High degree of safety:
    Safety functions are seamlessly implemented in SIL 2 (EN 61508) and PL d (EN ISO 13849-1)

  • High degree of flexibility:
    Practical safety and operator concepts can be realized

  • High degree of cost effectiveness:
    Hardware and installation costs are reduced

  • Higher degree of availability:
    Electromechanical switching elements that are prone to faults are eliminated