BONFIGLIOLI Agile Applications Manual page 22

If the function STO is triggered, the high level controller (PLC) has no more influence on the inverter
release 1 in the frequency inverter. To restart, the inverter release is enabled by the release by the user
or by the superior PLC.
An error inside the STO self-monitoring is identified and can then be repaired (e.g. by replacing of a
unit). Internally in the device the two stop paths are monitored cyclically beginning with the terminal
and ending with the power semiconductor. Both stop paths are designed identically.
One single error will not result in a failure of the safety function.
The test required for monitoring is performed by the frequency inverter automatically. If the test results
negative, the frequency inverter cannot be switched on anymore. Starting is possible again only after
the frequency inverter was completely disconnected from voltage supplies and error has been corrected.
Truth table
In the truth table, the states of the safety-relevant inputs STOA and STOB for activation and deactivation
of the safety function STO are listed.
STOA STOB Description of state
Safety function "Safe Torque Off" (STO) has been triggered. The frequency inverter sig-
0 0
nals no error in STO function. The inverter release is interrupted.
STO is triggered. Monitoring for error in frequency inverter or external circuitry (5-se-
cond monitoring). After 5 seconds, an error is signaled.
0 1
The inverter release is interrupted.
1 0
STO is not triggered. Release for operation.
1 1 Only in this state starting signals are accepted by the frequency inverter and lead to a
switching of the modulation.
5-second monitoring
It will be checked if the two inputs STOA or STOB are switched on within an interval of less than 5 sec
for requesting the release of the frequency inverter output stages.
If function STO is triggered by removing one of the signals from inputs STOA or STOB, the status
changes to "STO triggered" and the output stage is inhibited. In this state the monitoring function
checks, that during the next 5 seconds the second input is switched off. If this has not been done within
5 s after occurrence of this state, an error is triggered (5-second monitoring).
 Different signal states on inputs STOA or STOB start the 5-second monitoring

Within 5 seconds, the same signal must be present of both inputs, otherwise an error will be
signaled (F1205)
If the STO function is triggered on one channel, in the next following 5 s the STO function

must be triggered on both channels.

The error F1205 can be acknowledged using the Fault reset to reset the drive.
Behavior of frequency inverter after start
1 If the inverter release is interrupted, a motor revolving field can no longer be generated in this state.
22
Truth table
AGL-STOV0-01SV0-06 03/18