Formula and Method
For DC and single-phase circuits, Vd = 2 x I x rho x L / S. For three-phase circuits, Vd = sqrt(3) x I x rho x L / S.
Assumptions
- Approximate conductor resistivity at normal temperature
- Reactance and installation temperature effects are not included
- One-way length is used
Important Warnings
- Use project voltage-drop limits and local electrical code for final design.
- Long runs, high temperature, and grouped cables need additional derating.
FAQ
Why does the tool ask for one-way length?
The formula adds the return path internally for DC and single-phase circuits. Enter the physical one-way cable run.
Does this replace a full cable sizing calculation?
No. It checks voltage drop only. You still need ampacity, protection coordination, installation method, and fault-current checks.