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

Safety functions 127

Safely-limited speed (SLS)

The SLS prevents the motor from exceeding user-defined speed limits. The drive
limits the motor speed so that it stays between the SLS speed limits.
If the motor speed is above/below the user-defined SLS limit positive/negative when
the SLS function is activated, the motor speed is first decelerated to the required
speed. You can configure the SLS function to use either the time monitoring or ramp
monitoring method when the motor speed is decelerated.
Time monitoring
If the motor speed does not reach the desired SLS speed limit within a given time
(SLS time delay), the FSO starts to monitor the motor speed. If the motor speed is
above/below the SLS trip limit positive/negative, the FSO activates the SSE function
(see section SLS with time monitoring and speed above monitored speed on
page 129).
Ramp monitoring
Ramp monitoring limits are given with five SAR parameters, which define a "window"
within which the motor speed must stay during deceleration (see section Ramp
monitoring on page 51). If the motor speed reaches a ramp monitoring limit, the FSO
module activates the STO function (see section SLS with ramp monitoring and speed
above monitored speed on page 131).
Note: If the SLS monitoring must be activated immediately after the SLS request,
regardless of the current speed, time monitoring with a zero time delay (parameter
SLSx.04) must be used instead of ramp monitoring.
When the SLS monitoring is active, the drive limits the motor speed, but if the motor
speed still reaches the positive or negative SLS trip limit, the FSO module activates
the SSE function (see section SLS trip limit hits on page 133).