ABB ACS880 Series Manual page 24

24 Option description
Value of parameter SLSx.05
SLS ramp modoff reaction
Modoff delay time
Monitoring active
Monitoring active and modoff
delay time
Monitoring and modoff delay
time disabled
1) Time monitoring: The time monitoring counter does not increase when the drive is not modulating. If modulation does not
return, SLS indicates safe state after coast time defined by parameter STO.14 has elapsed. If modulation returns within
the specified time:
• with the motor speed below the SLS trip limit at that time, SLS monitoring starts and the SLS output indicates a safe
state
• with the motor speed above the SLS trip limit at that time, the drive trips because of a SLS trip limit hit.
Note: When encoder feedback is used, parameters SLSx.05 and SLSx.06 have no effect.
Example 1: Modoff delay time – modulation returns before modoff delay
In this example, parameter SLSx.05 is set to Modoff delay time. The time diagram below
describes the operation of the SLS function when modulation is lost during the deceleration
ramp, and the modulation returns before the modoff delay time has run out.
Motor speed
A
A SAR1 ramp monitoring
B Actual motor speed (coasting after modoff)
C SLS trip limit
D SLS limit
When modulation is lost
Ramp monitoring (SAR1) is disabled,
Time monitoring is suspended.
Last valid speed frozen and used.
Last valid speed frozen and used.
Ramp monitoring (SAR1) is disabled,
Time monitoring is suspended.
A
B
When modulation comes back
Ramp monitoring (SAR1) is restarted,
1)
Time monitoring is continued.
New speed taken into use.
New speed taken into use.
Ramp monitoring (SAR1) is restarted,
1)
Time monitoring is continued.
C
D
SLS request
SAR1 monitoring
Drive modulation
SLSx.06 Modoff
delay time monitoring
SLS monitoring
SLS indication
1)
1)
Time