Smooth Start Function
The Smooth Start function allows the starting comfort to be improved in applications with high stiction.
The Smooth Start function provides an extra ramp at the start of travel before accelerating to the provided speed reference form the controller.
As stated above Smooth Start should be used at a low speed value to overcome any stiction. Below is an example scope trace on how Smooth Start should look in an elevator application.
Smooth Start should only be used for a short time to improve starting performance. By adding a extra ramp before the normal travel curve you will feel reduced vibrations and a better quality start in stiff applications with high stiction.
Figure 11. Smooth Start Example Scope  Smooth Start does not need any Digital Inputs to activate and is solely done through the parametrisation steps above. | Figure 12. Smooth Start Timing Diagram  Smooth Start does to replace the normal S-Ramp but instead adds an extra one. Once Smooth Start finishes the standard acceleration parameters are used. |
Smooth Start is disabled by default and needs to be enabled. To do this follow the step by step guide below.
Setup drive following the standard commissioning procedure.
Set the Smooth Start time in P9-08. This will be the period that the drive runs at Smooth Start Speed for.
Then set the Smooth Start Speed in P9-09. This will be the speed that the drive will initially accelerate to.
Note
Both Steps 3 and 4 must be completed for Smooth Start to be active if either parameters mentioned have a value = 0, then Smooth Start will be disabled.
Once Smooth Start is active set them ramp time in P9-10. This will be the time it takes to accelerate from 0 to your chosen speed set in P9-09.
Below shows the conditions for Smooth Start to be active. If these conditions are not met then the travel profile will not include the Smooth Start Ramp.
Smooth Start does not have a dedicated enable setting from the Digital Inputs and is solely done through paramaterisation by giving both P9-08 and P9-09 values > 0.
Parameter Number | Parameter Name | Units | Default | Available Settings | Access | Change During Run | Scaling | Size (Bytes) | CAN Register | CAN Sub Index | Modbus Register |
|---|---|---|---|---|---|---|---|---|---|---|---|
P9-08 | Smooth Start Time | sec | 0.0s | 0.0 ... 5.0s | RW | Y | 1 = 0.1 s | 1 | 238Ch | 0 | 908 |
P9-09 | Smooth Start Speed | Hz / rpm / ft/s / m/s | 0.00Hz | 0.00 ... P8-01 | RW | Y | 1 = 0.01Hz | 2 | 238Dh | 0 | 909 |
P9-10 | Smooth Start Ramp Time | sec | 0.50s | 0.00 ... 600.00s | RW | Y | 1 = 0.01 s | 2 | 238Eh | 0 | 910 |
Sets the time that the Smooth Start Function is active for once the drive reaches the speed set in P9-09.
Must have a value > 0 for Smooth Start to be active.
Sets the target speed for the drive during the Smooth Start Function.
Must have a value > 0 for Smooth Start to be active.
Sets the ramp time to reach the target speed set in P9-09.