Estimate a rough current-density cable area, review length-related reflected-wave concern, and compare shielded versus unshielded planning choices.
This VFD cable sizing tool is a planning guide only. Final drive-to-motor cable selection must follow the drive manufacturer, motor insulation rating, EMC requirements, allowable cable length, and local code rules.
A variable frequency drive changes the way a motor cable behaves. The fast switching edges from the drive can increase common-mode noise, reflected-wave stress, and insulation stress, especially on longer cable runs. Because of that, VFD cable sizing is not only about current; cable type and distance matter too.
This VFD cable sizing tool uses motor current, cable length, carrier frequency, and cable type to produce a rough planning estimate and installation warnings. It is aimed at industrial electricians, maintenance teams, and engineers who need a quick field-friendly check before a more detailed design review.
It is particularly useful for deciding when shielded cable should be preferred and when a long drive-to-motor cable may justify a dv/dt filter or sine filter.
| Variable | Meaning | Unit |
|---|---|---|
| Ifull-load | Motor full load current | A |
| Idesign | Motor current after design margin | A |
| A | Estimated conductor area | mm2 |
| Carrier frequency | Drive PWM switching frequency | kHz |
| Cable length | Drive-to-motor cable distance | m |
Motor current is entered in amperes, cable length in meters, and carrier frequency in kilohertz. The output gives a rough current-density area estimate in square millimeters plus practical comments on shielding and long-cable behavior.
Motor current = 42 A, cable length = 35 m, carrier frequency = 4 kHz, shielded cable, margin = 125%.
Design current = 52.5 A
Using a planning current density of 5 A/mm2 gives a rough area estimate of 10.5 mm2.
A standard cable size above that value may be considered only after manufacturer cable and ampacity checks.
Motor current = 28 A, cable length = 120 m, carrier frequency = 12 kHz, unshielded cable, margin = 125%.
Design current = 35 A
The length and switching speed push the installation into a higher reflected-wave concern range.
A shielded cable and output filter review would be recommended.
This calculator uses a rule-of-thumb engineering approach rather than a manufacturer-specific model. Real VFD cable choice depends on drive insulation class, dv/dt limits, grounding method, EMC compliance requirements, cable construction, and the recommendations from the drive supplier. Use this page as a quick planning and troubleshooting tool, then verify the final installation against the actual equipment documentation.