Danfoss VLT FC 280 Operating Manual page 60

VLT® Midi Drive FC 280
Operating Guide
f
A
1
3
Illustration 32: Safe Stop 1 Time Controlled
A Actual frequency
1 Activation of SS1-t
2 Activation of Safe Torque Off
SS1-t function activates a braking ramp defined from a selected time delay in parameter 42-42 Delay Time, which means the braking
ramp is linear. Select the value of parameter 42-43 Delta T (the percentage of delay time), which is a reasonable tolerance before the
SS1-t time expires.
For SS1-t, ramping down the motor is performed by non-safety components, so it may fail undetected. Therefore, SS1-t cannot be
applied if this failure can cause a dangerous situation in the final application.
The SS1-t function does not monitor the reality of motor's stopping. If any drive's fault occurs before SS1-t time expired, the drive
coasts immediately regardless of the motor speed.
-
Assess the suitability of SS1-t for end application.
Using SS1-t may result in the motor still spinning when the Safe Torque Off is activated. The risk analysis for the machine must
indicate that this behavior can be tolerated. An interlock may be required.
The parameter 42-43 Delta T only provides a time margin with hope of the drive could stop before STO is activated. Too much of
Delta T can bring a steep ramp down curves, which may cause overcurrent and coast the motor.
60 | Danfoss A/S © 2022.02
t
4
2
N O T I C E
N O T I C E
W A R N I N G
N O T I C E
3
Parameter 42-42 Delay Time
4
Parameter 42-43 Delta T
AQ381425076031en-000101 / 130R1223
Safety Functions