Operation Principle; Sls Function; Sls With Speed Below The Monitored Speed - ABB ACS880 User Manual

Operation principle

SLS function

￭
The Safely-limited speed (SLS) function limits the motor speed so that it does not exceed
the user-defined speed limits when the function is active. The user defines the SLS limits
and trip limits. When the user activates the SLS function, the FSO modules send a SLS
request to the inverter units . The inverter units take the SLS parameters into use and control
the motor speed accordingly until the user deactivates the SLS request.
If the motor speed is above the user-defined SLS trip limit when the SLS function is activated,
the drive first decelerates the motor speed to the SLS limit. The FSO module monitors the
deceleration to the required speed with the time or ramp monitoring method.
Note: It is a good practice to define the motor speed reference so that it stays between the
SLS limits in the operating situations when the SLS function is active.
If the motor speed reaches the user-defined SLS trip limit, the FSO module activates the
Safe stop emergency (SSE) function. Depending on parameter settings, the SSE function
activates the inverter unit Safe torque off (STO) immediately, or after a deceleration ramp.
The motor coasts to a stop, or decelerates to zero speed.
There are four separate SLS functions in the FSO module with different parameter settings.
In the examples below, and in the delivered default settings of the +Q966 option, the SLS1
function is used.
For more information, refer to chapter
manual.

SLS with speed below the monitored speed

This time scheme diagram illustrates the operation of the SLS function. The motor speed
is below the monitored speed when the user activates the SLS function.
Motor speed
A
B
1 2
A Safety function response time
B SLS1 limit positive (parameter 200.23)
C SLS1 trip limit positive (parameter SLSx.14)
D Time to zero speed: Time from the STO activation to the moment when the acknowledgment be-
comes allowed (parameter STO.14). You must set this to the estimated time in which the motor
coasts to a stop from the maximum speed. Relevant only if 2b occurs.
Parameter settings
STO.14
D
2b
and the FSO module user's
C
3b 3
Option description 17
Time
SLS request
SLS status &
indication