DinSketchPrepare the line parameters
Determine load current, line length and conductor area. Supply resistance and reactance parameters where the selected model uses them. For AC calculations, confirm power factor and the supply configuration. Supply voltage also allows the drop to be expressed as a percentage.
Read the result in context
Compare the absolute drop in volts and the relative drop in percent. Higher current or greater length generally increases the drop. A larger conductor area reduces resistance. Confirm the circuit model before applying results to a different system.
Check more than voltage drop
An acceptable voltage-drop result does not establish cable thermal capacity, fault disconnection or correct protection. Check ampacity, installation method, temperature and protective-device characteristics separately.
Questions and answers
Why does cable length matter?
Conductor resistance increases with length, affecting the voltage at the load.
Can I size a cable only by voltage drop?
No. Ampacity and protective-device coordination require separate checks.