Operation
Step
Initial status: The drive is in operation and the motor is
not
running.
The user activates the Prevention of unexpected start-up function by switching off the POUS switch
[S].
1
The POUS safety relay [A65] switches off the XSTO inputs IN1 and IN2 of the inverter control unit
[A41]. The STO is now activated.
2
The drive indicates the status. See section Activating the safety function.
The POUS indication lamp [P] switches on.
3
The motor coasts to zero speed (if running) and the drive cannot start the motor while STO is active.
4
Normal operation resumes after the user:
5
• switches on the POUS switch [S]
• resets the drive (if the drive tripped on a fault)
• makes sure that the drive has received the start signal (depends on the configuration, see the
firmware manual).
Fault reaction function
Definition:
A safety function requires a “fault reaction function” that attempts to initiate a
safe state if the safety function's diagnostics detect a fault within the hardware/software that
performs the safety function.
The fault reaction function of the POUS safety relay trips the system if it detects a failure
(short circuit between signals, open circuits, redundancy fault when the POUS switch is
pressed) in the safety circuit consisting of, for example, POUS activation button and the
contacts wired to it.
The fault reaction function shifts the system immediately into safe state by switching on the
POUS command, activating the STO function, and keeping safe state activated and the
POUS indication lamp on until the detected fault has been fixed and safety function has
been reset.
The STO function has its own internal fault diagnostics and fault reaction function.
Parameter settings
■
Drive parameter settings
The parameter setting in ACS880 primary control program:
Description
Default value
Name
No.
Selects which indications are given when one or both Safe
torque off (STO) signals are switched off or lost.
Warning/Warning
STO indication
run/stop
31.22
Warning/Warning
is the recommended setting.
■
Additional parameter settings for ACS880-07 drives, frames nxDXT +
nxR8i and ACS880-17/17LC/37/37LC drives, frames nxR8i + nxR8i
Note:
ACS880 primary control program controls the inverter unit by default. There are
dedicated control units for the supply and inverter units.
The supply unit parameter settings in the ACS880 supply control programs:
Option description 17