Two-Channel Monitoring - BONFIGLIOLI Vectron ACTIVE CUBE Applications Manual

Triggering of function "Safe Torque Off"
Safe Torque Off can be achieved by:
− Intentional triggering during operation in order to stop a drive and safely prevent restarting, e.g.
for maintenance work on a machine.
− Triggering by actuation of an emergency stop switch or monitoring of protective systems, e.g.
safety door.
− Detection of an error. The drive may only start again after the error has been acknowledged and
eliminated.
Detection of an error through self-diagnosis
Application example:
The danger zone near a transport conveyor is monitored by a light grid. If anybody enters the danger
zone, the light grid is interrupted. The DC 24 V supply for the digital inputs STO of the function „Safe
Torque Off" is switched off and the frequency inverter output stage is disabled. The drive coasts to a
standstill. Disconnection from mains supply is not necessary. Communication via field bus or address-
ing via the terminals is still possible. An external brake which stops the motor can be addressed.
6.1

Two-Channel Monitoring

The STO function (Safe torque off) is realized via two channels in the frequency inverter (redundant
design). Via two redundant monitored stop paths with no-voltage release (STOA and STOB), the fre-
quency inverter is switched off safely even if an error occurs and the control voltage fails at the same
time. Thus, the drive is stopped safely if an error occurs. An error is identified and can then be re-
paired (e.g. by replacing of a unit). Triggering can be effected, for example, via a two-channel contac-
tor control with two release circuits and redundant disconnection of the main current or via a sensor
or emergency stop switch with two contacts and separate cable routing to the evaluation unit.
The stop paths are monitored cyclically every 32 ms. Both stop paths are designed identically.
Via the digital inputs S1IND (STOA) and S7IND (STOB), two DC 24 V control voltages of a protection
device are applied. If the protection device is actuated, the control voltages are interrupted and the
pulse block is activated; energy supply to the motor is switched off. Disconnection is effected at a
delay of less than 10 ms.
If the function STO is triggered, the overriding controller has no more influence on the pulse block
the frequency inverter. To restart, the pulse block has to be reset and a release commanded by the
operator or the superior PLC.
One single error will not result in a failure of the safety function.
1
If the pulse block is set, the controller release is reset. If the pulse block is set, no motor revolving
field is generated.
22
Actuation of safety relay
Safe Torque Off
1
in
ACU-STOV1-01SV2-04 en
09/14