ABB FSO-21, User Manual

Page: 162 / 540

162 Safety functions
Step Description
1 The SLS request is received. The motor speed is above the SLS trip limit positive (A).
The drive starts to ramp down the motor speed.
The FSO starts the counter for the SLS time delay (C) (parameter
SLSx.04 ).
The drive (parameter 23.13 or 23.15) defines the deceleration ramp until the speed
reaches the SLS limit.
2 The drive trips on a fault, there is a drive power loss, or user stops the drive by coast
stop.
STO.14 delay starts.
As the modulation is lost, FSO's safe speed estimation is stopped and it starts to use
the last speed information that it had before the modulation was lost.
3 Modulation of the drive has not returned and the safe speed estimation with the last
valid speed information of the motor speed is above the SLS trip limit after the SLS time
delay has elapsed. FSO module activates the SSE function. SSE function triggers STO
function because the modulation is lost and it cannot activate any deceleration ramp in
this case. For more information, see section
SLS trip limit hits on page 167 .
If the modulation returns before the last valid speed estimation of FSO has hit the SLS
time delay limit, the drive will continue the deceleration until SLS monitoring or time
monitoring limit is reached. If the motor speed is above the SLS trip limit after the SLS
time delay has elapsed, the FSO module activates the SSE function.
4 If modulation does not return, SLS indication goes on after STO.14 delay has elapsed.