Learn Automation with MINATA #38: Commissioning a VFD — From the Nameplate to a Controlled First Run
Commissioning a VFD: From the Nameplate to a Controlled First Run
Setting up a drive is not typing a few numbers and pressing Run. A good commissioning session needs the motor record, a mechanical check, safe limits, a way back if something goes wrong, and a backup of the data. The goal of the first run is modest and specific: the motor turns the right way, at the right speed, against the right load. Optimisation comes after that, not instead of it.
Before you give the run command
- Read the manual for the exact drive model, and the nameplate of the motor actually fitted.
- Confirm the incoming supply, the motor connection, PE, the mechanical condition and the safe area around the machine.
- Uncouple the load or run unloaded if the process allows it.
- Agree how you will stop, who is watching, and what conditions permit a test run at all.
- Save the existing parameter set before you change anything.
Do not insulation-test through a drive that is still connected to the motor unless the manual explicitly allows it. The measurement itself and the order of disconnection both follow the equipment documentation.
A practical order of work
- Enter the motor data correctly: voltage, current, power, frequency and speed.
- Choose the control mode and the source of the command and setpoint, as designed.
- Set the speed limits and the initial ramps conservatively.
- Check the direction of rotation at low speed, with the area clear.
- Raise load and speed gradually, watching current, vibration, temperature and fault status.
- Verify the feedback to PLC and HMI, the normal stop, and whichever safety functions apply.
- Save and name the parameter set that was accepted.
The parameters that get taken lightly
- Ramps: too short trips on overcurrent or makes the mechanism slip; too long and the process no longer keeps up.
- Frequency limits: they keep the mechanism out of speeds it was never built for.
- Automatic restart: only where the risk assessment permits it and the operator has been warned.
- Command source: local keypad, terminals, analogue or fieldbus — it has to agree with what the HMI and PLC expect.
- Braking: a high-inertia load may need a designed braking solution, not an endlessly stretched deceleration ramp.
Control modes: V/f, sensorless vector and closed loop
| Mode | Character | Suits |
|---|
| V/f (scalar) | Simple and stable, weak torque at very low speed | Pumps, fans, light conveyors |
| Sensorless vector | Good torque at low speed, no encoder needed | Heavy conveyors, extruders |
| Closed-loop vector (with encoder) | Accurate torque and speed even near zero | Hoisting, winding, anything needing precise torque |
Conservative starting values for the main parameters
| Parameter | What it does | Risk of getting it wrong |
|---|
| Accel / decel ramp | Time taken to reach speed | Too short trips on overcurrent; too long slows the cycle |
| Current limit | Protects drive and motor | Too low loses torque; too high loses protection |
| Min / max frequency | Blocks forbidden mechanical regions | Ignoring it invites resonance or overspeed |
| Command and setpoint source | Local, terminals, analogue or fieldbus | Inconsistent, and the machine simply ignores the command |
Start with ramps longer than you think you need and a current limit taken from the nameplate, then tighten them once you understand the mechanism. That is safer than setting neat-looking values on day one.
A worked engineering situation
A conveyor motor is set up from its nameplate and first jogged at low speed to confirm direction. The PLC issues Start through the control circuit; the HMI shows the setpoint, the speed feedback and any fault. Once it has run under load, the team adjusts only the ramps, and only within the limits already recorded, then backs up the parameter set together with the machine number and the commissioning date.
The final thresholds have to be approved against the motor, the mechanism, the drive and the manufacturer's instructions.
Parameter handover checklist
- [ ] A photograph of the motor nameplate and a drive backup file both exist.
- [ ] Motor data, control mode and command source are written down.
- [ ] Direction, minimum and maximum speed and the ramps have all been run.
- [ ] The PLC and HMI read real status and real faults.
- [ ] Restart and stop behaviour was tested within a safe scope.
With the drive commissioned, #39 helps you tell the two apart: when a VFD is the right answer, and when the application actually needs a servo.
Read more automation knowledge at MINATA: https://minatavn.com/en/blog/industrial-automation
Previous — #37: The variable frequency drive: principles and limits: https://minatavn.com/en/blog/automation-37-vfd-principles
Next — #39: Servo against VFD: https://minatavn.com/en/blog/automation-39-servo-vs-vfd
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