Description Of Active Cube Safety Function - BONFIGLIOLI ACTIVE CUBE Series Applications Manual

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The frequency inverters of the ACU series of devices feature the integrated safety
function „Safe torque off, STO".
In the case of an error or if requested, the power semiconductors of the frequency
inverter will be switched off. After this, the frequency inverter does not supply energy
to the drive which would cause a revolution or a torque (or a movement or force in
the case of a linear drive). Mains voltage is still present. The function STO can be
used, for example, for safe stopping in the case of a dangerous situation or for main-
tenance work on the machine. If an error occurs, the machine can still be (or remain)
switched off safely.
Unlike shut-down via mains contactors or motor contactors, the integrated safety
function enables easy combination of drives in a machine to form functional groups.
The Safe Torque Off can be limited to certain plant areas in this way. Another advan-
tage is the fact that it is not necessary to wait until the frequency inverter has been
charged and discharged. Thus, readiness of the machine for operation can be res-
tored more quickly. Regular electro mechanic equipment are wearing out – through
the usage of the STO functionality, this kind of equipment is no longer necessary and
maintenance costs can be reduced.
Safe Torque Off:
− Energy supply for the rotary field of the motor is interrupted; the motor coasts to
a standstill
− Used if monitoring for standstill is not required
− Accidental start of the motor is prevented
− No galvanic isolation of motor from frequency inverter DC link
Traditional System
Frequency inverter
K1
Further advantages:
− Contactors on motor side not required, reduced installation
requirements, less components, more space in electrical cab-
inet
− Simple realization with external safety control device
− The drive can be connected to power supply continuously;
communication and parameter configuration of the frequency
inverter are maintained while the torque is disabled.
− Easier machine approval, because the safety function is certi-
fied via a type examination check.
ACU-STOV1-01SV2-03 en
03/11

Description of ACTIVE Cube Safety Function

Mains
M
Integrated System
with ACU and usage of STO
Mains
ACTIVE Cube
with integrated
Safety function
M
Safe Torque Off
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