8
"Safe Torque Off (STO)" function
8.1
General
•
The "Safe torque off (STO) function in the ZAdynpro product series corresponds to the "Safe torque
off (STO)" stop function in accordance with DIN EN 61800-5-2.
•
Activation of this function ensures that the ZAdynpro cannot supply any energy to the motor which
can cause a torque.
•
The STO function allows the contactors that are usually installed between ZAdynpro and motor in
lifts to be omitted. The requirements in accordance with EN 81-20 section 5.9.2.5.4 d) or section
5.9.3.4.2 d) are ful
fi
lled.
•
The STO function must be taken into consideration in an application-speci
fi
c risk analysis by the
company responsible for the start-up. This company is also responsible for considering other valid
safety regulations as well as the de
fi
nition of the requirements for the component which control the
STO function in compliance with standards.
Danger
There is no active braking when the STO function is activated. The drive stops gradually. This must be
taken into consideration in applications in which there might be a hazard (e.g. by vertical loads). Active
braking must be implemented by additional measures (e.g. by a mechanical motor brake).
8.2
Safety concept
•
The24devices of the ZAdynpro series have two safety-related inputs (two-channel structure). The
drive can only generate a torque when a V switching signal is applied to both of these inputs. When
the two 24V switching signals are switched off, the STO function is activated and the activation of
the switching transistors (IGBTs) is safely prevented.
•
An internal diagnostic unit constantly compares the status of the two switch-off channels (STO_A
and STO_B). If there is an error (unequal activation or an internal hardware defect), the internal
diagnostic unit triggers switch-off of the drive.
•
Both inputs must be activated via two separate relays whose control voltage is supplied at the end
of the electrical safety chain (see Chapter "Safe torque off (STO) function/Principle circuit dia-
gram").
Information
In the version according to the principle circuit diagram, monitoring of the two relays K1/K2 by the lift
control system is not necessary in order to meet the requirements of EN 81-20. The requirements are
met by the internal diagnostic unit.
•
If the contacts are switched differently (e.g. one of the two relays does not open), this will be
detected at the STO inputs by the different signals. In this case the internal diagnostic unit will turn
off safely after a max. 1600 ms. In this case, a reset is only possible by switching the device off and
on again.
•
The status of the STO function can be queried optionally (not safety-related) via the digital output
"STO-Info".
Danger
The connected motor is not separated from the ZAdynpro by activation of the STO function. Therefore,
you must disconnect the ZAdynpro from the supply voltage in order to perform work on the wiring or
the motor. You must waitat least Allow 3 minutes for discharging the intermediate circuit capacitors.
The safe isolation from the supply must be checked using a two-pole voltage detector.
Danger
If the drive is enabled again after being disabled by the STO function, the drive can restart
automatically. If this is not admissible for the application, this must be implemented by external
measures (restart e.g. only after con
fi
rmation).
Original operating instructions
ZAdynpro
–
Part 1
"Safe Torque Off (STO)" function
R-TBA17_01-GB 1837 Index 004
Part.-No. 00163459-GB
44/64
