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Unidrive M / Unidrive HS Modular Installation Guide

131

Issue Number: 5

6.17 Safe Torque Off (STO)

The Safe Torque Off function provides a means for preventing the drive
from generating torque in the motor, with a very high level of integrity. It
is suitable for incorporation into a safety system for a machine. It is also
suitable for use as a conventional drive enable input.

The safety function is active when the STO input is in the logic-low state
as specified in the control terminal specification. The function is defined
according to EN 61800-5-2 and IEC 61800-5-2 as follows. (In these
standards a drive offering safety-related functions is referred to as a
PDS(SR)):

'Power that can cause rotation (or motion in the case of a linear motor) is
not applied to the motor. The PDS(SR) will not provide energy to the
motor which can generate torque (or force in the case of a linear motor)'

This safety function corresponds to an uncontrolled stop in accordance
with stop category 0 of IEC 60204-1.

The Safe Torque Off function makes use of the special property of an
inverter drive with an induction motor, which is that torque cannot be
generated without the continuous correct active behaviour of the inverter
circuit. All credible faults in the inverter power circuit cause a loss of
torque generation.
The Safe Torque Off function is fail-safe, so when the Safe Torque Off
input is disconnected the drive will not operate the motor, even if a
combination of components within the drive has failed. Most component
failures are revealed by the drive failing to operate. Safe Torque Off is
also independent of the drive firmware. This meets the requirements of
the following standards, for the prevention of operation of the motor.

Machinery Applications

The Safe Torque Off function has been independently assessed by
Notified Body, TüV Rheinland for use as a safety component of a
machine:

Prevention of unintended motor operation: The safety function “Safe
Torque Off” can be used in applications up to Cat 4, PL e according to
EN ISO 13849-1, SIL 3 according to EN 61800-5-2/ EN 62061/ IEC
61508 and in lift applications according to EN 81-1 and EN81-2.

This certificate is available for download from the TüV Rheinland website
at: http://www.tuv.com

Safety Parameters as verified by TüV Rheinland:

According to IEC 61508-1 to 07 / EN 61800-5-2 / EN 62061

According to EN ISO 13849-1

Logic levels comply with IEC 61131-2:2007 for type 1 digital inputs rated
at 24 V. Maximum level for logic low to achieve SIL3 and PL e 5 V and
0.5 mA.

Lift (Elevator) Applications

The Safe Torque Off function has been independently assessed for use
as a safety component in lift (elevator) applications by Notified Body,
TüV Nord:

The Unidrive M drives series with Safe Torque Off (STO) function if
applied according to the "Conditions of application" fulfil the safety
requirements of the standards EN81-1, EN81-2, EN 81-50 and
EN60664-1and are in conformity with all relevant requirements of the
Directive 95/16/EC.

The Safe Torque Off function can be used to eliminate electro-
mechanical contactors, including special safety contactors, which would
otherwise be required for safety applications.
For further information contact the supplier of the drive.

UL Approva

The Safe Torque Off function has been independently assessed by
Underwriters Laboratories (UL). The on-line certification (yellow card)
reference is: FSPC.E171230.

Safety Parameters as verified by UL:

According to IEC 61508-1 to 7

According to EN ISO 13849-1

Type examination
certificate number

Date of issue

Models

01.205/5270.01/14

11-11-2014

M700, M701,
M702, HS70,

HS71, HS72

Type

Value