ABB FSO-21, User Manual

Page: 48 / 540

48 Overview
available for both safe speed estimate and safety encoder feedback. The mute time
feature can be especially useful with the safe speed estimate because the estimate is
more prone to spurious trips caused by for example rapid changes in motor torque.
The mute time should be set as short as possible.
With safe speed estimate, there are two options to implement the mute time feature in
the FSO. By default, general mute time parameter
FSOGEN.31 is used for all speed
functions. Starting from FSO rev. J, it is also possible to enable function-specific mute
times for limit hit situations with parameters
FSOGEN.38 and FSOGEN.39 . With
safety encoder feedback, the general mute time parameter FSOGEN.31 is always
used. For more information, see section Mute time feature on page 64 .
Overview of safety functions
This section gives a short overview of the safety functions and gives references to the
detailed descriptions. For a description of the dependencies between the safety
functions, see section
Dependencies between safety functions on page 193 .

Safe torque off (STO)
This safety function activates the STO function in the drive, this is, opens the STO
circuit in the drive. The motor coasts to a stop (stop category 0). See section
STO
function on page 68 .
The FSO module activates the STO function and the motor stops, if:
• the motor speed reaches the SAR0, SAR1, or time monitoring (ie, SS1-t) limits, or
• the FSO detects an internal failure, or
• an encoder fault with FSE-31 occurs.

Safe stop 1 (SS1)
This safety function stops the motor safely by ramping down the motor speed to zero
speed (stop category 1). The FSO monitors the stop ramp either with the time or
ramp monitoring method (SS1 function types SS1-t and SS1-r, respectively). See
sections
• SS1 with time monitoring (SS1-t) on page 80 and
• SS1 with ramp monitoring (SS1-r) on page 84 .

Safe stop emergency (SSE)
This safety function stops the motor safely by coasting (stop category 0) or ramping
down (stop category 1) the motor speed to zero speed.