2.11 Safety Instructions on Function „Safe Torque Off“ (STO)
The function “Safe Torque Off” (STO) is a functional safety provision, i.e. it protects
staff from damage, provided that projecting, installation and operation are performed
properly. This function does not disconnect the plant from power supply.
To disconnect the plant from power supply (for example for service purposes) an
“Emergency Stop” circuit according to EN 60204 has to be installed.
For maintenance work, a provision must be provided for disconnecting the plant from
power supply.
WARNING
Improper installation of the safety technique can cause an uncontrolled starting of the
drive. This may cause death, serious injuries and significant material damage.
Safety functions may only be installed and commissioned by qualified staff.
The STO function is not suitable for emergency switch off as per EN 60204. An emer-
gency switch off 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 uncon-
trolled starting of the drive.
The drive is started again when the function STO is no longer triggered. In order to
comply with EN 60204, it must be ensured by taking external measures that the dr
does not start without prior confirmation.
Without a mechanical brake, the drive might 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 control by STO, ac-
cess 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
assessment. BONFIGLIOLI VECTRON recommen
ds that the check is performed after
one year, at the latest.
The STO function is one fault fail-
safe. No single fault or component failure can cause
a disabled drive to produce motor shaft torque. Only in extremely unlike combinations
of component faults the motor shaft could move jerky with sudden acceleration (max-
imum 180°/number of pole pairs, for example jerky movement of 90° for 4-pole mo-
tor, 180°/2) and produce torque. It must be checked if this behavior can cause a
dangerous machine movement.
If
the STO function is used, the special safety, installation and instructions on use
instructions shall be complied with.
Comply with the Application manual „Safe Torque Off STO“, especially when the de-
scribed safety relevant function is used.
06/13 Operating Instructions ACU 23
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