Safety functions 89
Step Description
1 The SS1 request is received (for example, from the I/O). The FSO starts a counter for
time B. SS1 state indication parameter SS1 output (SS1.21) goes on.
2 After time D has elapsed, the drive starts to ramp down the motor speed. SAR1
parameter 200.112 defines the deceleration ramp.
Note: If parameter 200.112 has value 0, the drive (parameter 23.23) defines the ramp.
3 The motor speed goes below the SBC speed limit (A), the FSO checks the value of
STO SBC delay (parameter SBC.12) and activates the SBC and drive STO functions:
• If the STO SBC delay is positive or zero, the SBC and drive STO functions are
activated at the same time (this case is shown in the figure).
• If the STO SBC delay is negative, the SBC is activated here and the drive STO after
this delay (see section SS1 with speed limit activated SBC, SBC before STO on
page 96).
• STO active indication parameter STO output (STO.21) goes on when STO is
activated.
The FSO starts a counter for time C.
Note: You can define an extra delay (parameter SS1.15) before the FSO activates the
SBC and drive STO functions (not shown in the figure).
3b If the drive has not ramped down fast enough when time B has elapsed, the FSO
activates the STO function. See section Safe torque off (STO) on page 67 for more
information on how to configure the STO function.
4 After time C has elapsed, the FSO defines the motor as stopped, the SS1 completed
output indication (parameter SS1.22) goes on and the acknowledgement becomes
allowed as soon as the SS1 request has been removed (step 5).
5 The SS1 request is removed.
6 After the acknowledgement, the SS1, STO and SBC functions are deactivated and the
control is given back to the drive, which is allowed to modulate again. The indications
SS1 output (SS1.21), SS1 completed output (SS1.22), and STO output (STO.21) go off.
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