Most conveyor VFDs are left at factory settings because the line runs. It runs, but the acceleration is too fast, the overload is too low and the stop is uncontrolled. The result is product shift, nuisance trips and mechanical wear.
Key takeaways
- Enter the motor data before anything else.
- Set acceleration and deceleration for the load, not for the drive.
- Use a controlled stop for conveyors, not a coast stop.
- Set the overload to protect the motor, not to mask a mechanical problem.
1. Motor data
Enter the motor nameplate data: voltage, frequency, current, speed and power. Run the autotune if the drive supports it. A drive that does not know the motor will not control it accurately.
Check the motor connection (star or delta) against the nameplate. A wrong connection will cause the drive to trip or the motor to overheat.
2. Acceleration and deceleration
For a conveyor, the acceleration should be slow enough that the product does not shift or tip. A ramp of 2–5 seconds is typical for a light conveyor; 5–10 seconds for a heavy or loaded conveyor. The deceleration should be similar or slightly longer.
If the product is unstable, use an S-curve ramp to reduce jerk at the start and end of the ramp.
| Parameter | Typical setting | Effect |
|---|---|---|
| Acceleration | 3–5 s | Product stability, current |
| Deceleration | 3–6 s | Product shift, brake wear |
| Overload | 110–120% motor FLA | Motor protection |
| Stop mode | Ramp stop | Controlled stop |
| Skip frequency | Per site | Resonance avoidance |
3. Overload and current limit
Set the overload to the motor's full-load current, not to the drive's maximum. A higher setting will allow the motor to overheat before the drive trips. A lower setting will trip on a normal start.
Set the current limit to about 150% of the motor current for a short time, enough to start a loaded conveyor. If the drive trips on start, check the mechanical load before increasing the limit.
4. Stop mode
Use a ramp stop, not a coast stop. A coast stop lets the load run on, which can cause a jam at the next station or a product collision. For an incline, use a brake motor or a regenerative stop.
For an emergency stop, the drive should stop according to the safety category. A controlled stop may not be appropriate for an E-stop; follow the risk assessment.
5. Skip frequencies
Every structure has a resonant frequency. If the conveyor vibrates at a particular speed, use the skip frequency function to avoid it. Set the skip band around the resonant speed and test at the production speed.
Do not use skip frequencies to mask a mechanical problem such as a bent shaft or a loose mount. Fix the cause first.
6. I/O and controls
Configure the digital inputs for start, stop, fault reset and any safety interlock. Configure the relay output for run and fault. Label the terminals and update the drawing.
If the drive is connected to a PLC, set the communication parameters and test the start/stop and the speed reference before production.
Frequently asked questions
Do I need a VFD on every conveyor?
No. A fixed-speed conveyor can use a direct-on-line starter. A VFD is useful for soft starts, speed matching and energy saving on variable loads.
What causes a VFD to trip on start?
Usually a mechanical load, a wrong motor data setting, too short an acceleration or an overload setting that is too low.
Can a VFD save energy on a conveyor?
Only if the conveyor runs at reduced speed for part of the cycle. A conveyor running at full speed all day will not save much.
For the mechanical checks before VFD setup, see installation and commissioning.
