ABB FSO-21, User Manual

Page: 339 / 540

Configuration 339
Encoder or FSE failure situations
The STO with speed limit activated SBC function (parameter SBC.11 STO SBC
usage = Speed limit ) requires the exact motor speed, and when this is not available,
the FSO module starts to use the Delayed brake selection (parameter SBC.11 STO
SBC usage = Delayed brake ).
If parameter S_ENCGEN.11 FSE diagnostic failure reaction = STO , the FSO module
goes into the Fail-safe mode and actives the STO with speed limit activated SBC
function with
Delayed brake :
• If parameter SBC.12 STO SBC delay is positive, the FSO activates the SBC
after this time has elapsed from the STO activation.
• If parameter SBC.12 STO SBC delay is negative or zero, the FSO actives the
SBC when the encoder failure occurs.
If parameter S_ENCGEN.11 FSE diagnostic failure reaction = No STO , and there are
no active safety functions, the FSO module sends a warning to the drive. If there are
active safety functions when the FSO module detects the failure, the FSO module
goes into the Fail-safe mode and actives the STO with speed limit activated SBC
function with
Delayed brake (see above).
If parameter S_ENCGEN.11 FSE diagnostic failure reaction = Est switch not active
load , the FSO module continues operation by using the estimated motor speed until
the encoder failure is fixed and the exact motor speed is available again. Note: Safe
speed estimate cannot be used with a DCS880 drive.
• If the encoder failure occurs before the STO function is activated, the FSO
continues operation using the estimated motor speed and activates the STO and
SBC function with
Delayed brake (see section How to configure SBC after STO
on page 333 ) when the STO function request is received.
• If the encoder failure occurs while the STO function is already active, but the STO
SBC speed has not been reached yet, the FSO module starts to use the Delayed
brake and activates the SBC accordingly:
• If parameter SBC.12 STO SBC delay is positive, the FSO activates the SBC
after this time has elapsed from the STO activation.
• If parameter SBC.12 STO SBC delay is negative or zero, the FSO activates
the SBC when the encoder failure occurs.