Safety functions 125
Step Description
1 The SSE request is received (for example, from the I/O). The FSO starts a counter for
time B. SSE active indication SSE output (SSE.21) goes on.
2 After time D has elapsed, the drive starts to ramp down the motor speed. SAR0
parameter 200.102 defines the deceleration 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 SSE with speed limit activated SBC, SBC before STO on
page 132).
• 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 SSE.16) 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 SSE completed
indication goes on and the acknowledgement becomes allowed as soon as the SSE
request has been removed (step 5).
5 The SSE request is removed.
6 After the acknowledgement, the SSE, STO and SBC functions are deactivated and the
control is given back to the drive, which is allowed to modulate again. The indications
SSE output (SSE.21), SSE completed output (SSE.22), and STO output (STO.21) go
off.
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