Variable Safely-Limited Speed (Sls) - ABB FSO-21 User Manual

Variable Safely-limited speed (SLS)

This safety function requires that a safety PLC is connected to the FSO module via
the PROFIsafe communication bus. For more information, see chapter PROFIsafe.
The SLS function prevents the motor from exceeding user-defined speed limits. With
the Variable SLS function, the speed limits can be changed on the fly. The speed
limits are controlled from a safety PLC via the PROFIsafe communication bus.
If the motor speed reaches the positive or negative SLS trip limit, the FSO module
activates the SSE function (see section
speed reaches a ramp monitoring limit during deceleration, the FSO module activates
the STO function. If the motor speed reaches a time monitoring limit during
deceleration, the FSO module starts to monitor the speed and if it is above/below the
SLS trip limit positive/negative, the FSO activates the SSE function.
Also a "non-variable" SLS function and the SMS function can be active at the same
time with the Variable SLS function. In this case, the FSO module monitors all limits
and limits the motor speed according to the lowest speed limit.
The safety PLC sends the Variable SLS request to the FSO module in a PROFIsafe
message. The message includes a scaling value as a percentage (%). The scaling
value is used to scale the original SLS and trip limits (SLS4 parameters) to new,
scaled values. The FSO module uses these scaled values until a new scaling value is
received the safety PLC.
The Variable SLS limits cannot be scaled above the SLS4 limits.
In the PROFIsafe message, the bits that are used to configure the Variable SLS
function are:
• Positive_Scaling: defines whether the positive SLS limits are scaled or not.
• Negative_Scaling: defines whether the negative SLS limits are scaled or not.
• Variable_SLS_limit (MSB and LSB): defines the scaling value. For example, if the
value set in Variable_SLS_limit = 5000, the scaling value is 50%.
The same scaling value is applied to both the positive and the negative limits. For
more information, see section
For more information on how the FSO module defines the scaled limits, see section
Defining the scaled SLS4 limit and SLS4 trip limits
SLS trip limit hits
ABB_PS1 profile F-Output user data
Safety functions 137
on page 133). If the motor
on page 167.
on page 303.