Voltage Drop Tool
Evaluate voltage drop in DC, single-phase and three-phase circuits using conductor material, cross-section, temperature, cable length and electrical load. Review load-end voltage, percentage drop, resistive losses, permissible limits, recommended conductor size and voltage profiles.
| Distance | Voltage | Drop (V) | Drop (%) |
|---|
Table of Contents
Highlights
- DC, single-phase and three-phase circuit support
- Copper or aluminium with adjustable conductor temperature
- Current, real-power and apparent-power load inputs
- Interactive voltage profile and distance breakdown table
- Voltage-drop limit check, cable loss and suggested size
How Voltage Drop Tool Works?
Current flowing through a conductor produces a voltage reduction because the cable has resistance. The resistance of one conductor is calculated using its cross-sectional area and temperature-adjusted resistivity:
Here, L is one-way conductor length, A is conductor area, and α is the temperature coefficient. At 20 °C, the model uses copper resistivity 0.017241 and aluminium resistivity 0.028264 Ω·mm²/m, with coefficients 0.00393 and 0.00403 per °C respectively.
Voltage drop depends on the supply system. AC calculations include power factor and the user-entered conductor reactance; DC uses resistance alone.
For AC, X is the entered reactance per conductor multiplied by one-way length; sinφ is calculated from the power factor. Current may be entered directly or derived from real power (I = P/(kV cosφ)) or apparent power (I = S/(kV)), where k is 1 for DC and single-phase, or √3 for three-phase. For DC, the real-power formula uses a power factor of 1.
Resistive cable loss is estimated as 2I²R for DC and single-phase, or 3I²R for three-phase. The results include cable-path resistance, power loss, a pass/fail comparison with the chosen percentage limit and the first passing conductor size from the built-in 1–300 mm² standard-size list. The distance table and interactive voltage profile assume a uniform cable and steady current.
Practical Use Cases
Domestic electricians: Examine whether a long single-phase branch circuit is likely to meet a specified voltage-drop limit, and compare conductor sizes before selecting a cable.
Solar and battery installers: Estimate DC voltage reduction between a battery, controller and connected equipment, including the effect of conductor size and operating temperature.
Industrial electrical designers: Investigate three-phase feeder voltage at the load and examine the influence of current, power factor and conductor reactance.
Workshop and facility managers: Compare resistive power losses across cable options when planning supply runs to machinery or other continuous loads.
Students and instructors: Explore how length, material, temperature and circuit configuration alter voltage drop using the plotted voltage profile and distance table.
Accuracy and Limitations
The tool uses fixed 20 °C material resistivities, linear temperature correction, uniform conductors and a steady, balanced load. Its AC formula is an approximate series-impedance voltage-drop expression, not a full phasor power-flow solution; it treats entered power factor as a positive lagging value and does not model leading reactive loads, harmonics, inrush current or changing load current along the run. DC and single-phase calculations assume two conductors, while three-phase assumes a balanced three-conductor circuit. The suggested size is chosen solely by the percentage-drop criterion and non-negative load voltage from a fixed 1–300 mm² list; it does not verify ampacity, protection, thermal installation conditions or applicable wiring regulations.
