Safety Instructions On Function "Safe Torque Off" (Sto) - BONFIGLIOLI Agile Applications Manual

3 Safety Instructions on Function "Safe Torque Off" (STO)

The function „Safe Torque Off" (STO) is a functional safety feature, i.e. it protects staff from damage,
provided that projecting, installation and operation are performed properly. This function does not dis-
connect the plant from power supply.
In order to disconnect the plant from power supply (e.g. for maintenance work), an "Emergency Stop"
provision as per EN 60204 must be installed.
WARNING
Uncontrolled Starting
Improper installation of the safety circuitry may result in uncontrolled starting of the
drive. This may cause death, serious injuries and significant material damage.
Safety functions may only be installed and commissioned by skilled personnel.
The STO function is not suitable for emergency stop as per EN 60204. An emergency
stop can be realized by installing a mains contactor.
An emergency stop according to EN 60204 must be functioning in all operation modes of
the frequency inverter. Resetting of an emergency stop must not result in uncontrolled
starting of the drive.
The drive is started again when the function STO is no longer required. In order to comply
with EN 60204, it must be ensured by taking external measures that the drive does not
start without prior confirmation.
Without a mechanical brake, the drive will not stop immediately but coast to a standstill.
If this may result in personal or material damage, additional safety measures must be
taken.
 If persons may be endangered after disconnection of the motor power supply by
STO, access to the hazard areas must be prevented until the drive has stopped.
 Check the safety function at regular intervals according to the results of your risk
analysis. Bonfiglioli Vectron MDS GmbH recommends that the check be performed
after one year, at the latest.
The STO function is fail-safe for one fault. However, on rare occasions, the occurrence of
component defects may cause jerking of the motor shaft (max. 180°/pole pair, e. g. jerk
by 90° with 4-pole motor, 180°/2).
 Check if this causes a dangerous movement of the machine.
 If the STO function is used, the special safety, installation and instructions on use
instructions shall be complied with.
WARNING
Dangerous voltage!
The safety function "Safe Torque Off" may only be used if mechanical work is to be
performed on the driven machines, not for work on live components.
After disconnection of an external DC 24 V power supply, the DC link of the frequency
inverter is still connected to mains supply.
Even if power supply to the motor is disconnected, and the motor is coasting to a standstill
or has already stopped, high voltages may still be present on the motor terminals.
Before working (e. g. maintenance) on live parts, the plant must always be disconnected
from mains supply (main switch). This must be documented on the plant.
When the function "Safe Torque Off" is triggered, the motor is not isolated from the DC
link of the frequency inverter. High voltage levels may be present at the motor.
 Do not touch live terminals.
The application manual "Safe Torque Off STO" must be complied with, particularly if the
safety function described there is used.
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