Application and selection overview
Key parameters for selecting a VFD by motor current, load, supply, control and environment.
Key parameters to confirm
| Item | Information to provide |
|---|---|
| Motor data | Rated power, voltage, current, frequency, speed, efficiency and winding connection. |
| Power supply | Input voltage, phase, frequency, expected variation and available short-circuit capacity. |
| Load profile | Variable-torque fan or pump, or constant-torque/heavy-duty conveyor, hoist or extrusion duty. |
| Control requirements | Start/stop method, speed reference, feedback, communication protocol and safety functions. |
| Installation | Panel or wall mounting, temperature, altitude, dust, humidity, enclosure and cooling. |
RFQ checklist
- Provide motor and existing drive nameplate photographs.
- State minimum and maximum speed, acceleration/deceleration time and starts per hour.
- List braking resistor, encoder, filter, reactor and communication options.
- Confirm cabinet space, cooling method and applicable electrical standards.
Common mistakes and risks
- Sizing only by motor power and ignoring rated current and overload curves.
- Using a light-duty fan/pump rating for a heavy constant-torque load.
- Ignoring long motor cables, harmonics, EMC or regenerative braking requirements.
Frequently asked questions
Can a VFD be added to an old motor?
Insulation, cooling, bearing currents, minimum speed and cable length must be reviewed; an output filter or separate fan may be required.
Is a larger drive always safer?
Excessive oversizing increases cost and can reduce current-measurement and protection effectiveness. Select by current, overload and derating.
Can an obsolete drive be replaced directly?
Mechanical size, terminals, parameters, communications, programs and safety functions must be compared, not just power.
Next step
Send the brand, complete drive model, motor nameplate, load type, control method, quantity and destination so compatibility and required options can be checked.
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