3 Phase Voltage Drop Calculator

Compute three phase voltage drop easily. Review losses, resistance, graphs, and exports. Design electrical feeders with confidence using practical input controls.

Use this calculator to estimate three phase voltage drop, receiving voltage, impedance, and feeder loss based on conductor size, temperature, power factor, cable length, reactance, and parallel runs.

Calculator Input

Load Entry Method

Line Voltage (V)

Power Factor

Load Current (A)

Used when direct current entry is selected.

Load Power

Power Unit

Efficiency (%)

Cable Length

Length Unit

Conductor Area (mm²)

Conductor Material

Conductor Temperature (°C)

Reactance (Ω/km)

Parallel Runs per Phase

Example Data Table

System Voltage	Current	Length	Material	Area	Power Factor	Approx. Drop
400 V	80 A	50 m	Copper	25 mm²	0.90	4.6 V
415 V	120 A	80 m	Copper	35 mm²	0.92	8.9 V
480 V	150 A	120 m	Aluminum	70 mm²	0.88	11.2 V

These values are illustrative only. Final design should follow local codes, installation method, cable grouping, harmonic content, and manufacturer data.

Formula Used

Three phase voltage drop:

Vdrop = √3 × I × (R × cosφ + X × sinφ) × L

Where:

I = line current in amperes
R = conductor resistance in Ω/km
X = reactance in Ω/km
cosφ = power factor
sinφ = √(1 − cos²φ)
L = one way cable length in km

Temperature adjusted resistance:

R_T = R₂₀ × [1 + α × (T − 20)]

Resistance at 20°C from conductor area:

R₂₀ = (ρ × 1000) / A

Current from power:

I = P / (√3 × V × cosφ × η)

Estimated power loss:

P_loss = 3 × I² × R_total

How to Use This Calculator

Choose whether you want to enter current directly or derive it from load power.
Enter the three phase line voltage and the expected power factor.
Provide cable length, conductor size, material, operating temperature, and reactance.
Set the number of parallel runs if more than one conductor shares each phase.
Click calculate to view voltage drop, receiving voltage, and estimated power loss.
Use the chart and export buttons to analyze or save the result.

Frequently Asked Questions

1. Why is three phase voltage drop important?

Excessive drop lowers equipment voltage, raises heating, reduces motor torque, and can cause nuisance tripping. It also wastes energy and may violate electrical design limits.

2. Does cable length mean one way or loop length?

This calculator uses one way length for three phase circuits. The equation already accounts for the three phase path, so do not double the entered distance.

3. Why does temperature change the result?

Conductor resistance rises as temperature increases. Higher resistance causes a larger voltage drop and greater power loss, especially on long feeders or heavily loaded circuits.

4. What role does power factor play?

Poorer power factor increases the reactive part of the current. That raises the voltage drop contribution from impedance, so the same feeder can perform worse under inductive loads.

5. Should I use copper or aluminum?

Copper usually gives lower resistance for the same area, while aluminum can reduce cost and weight. Final selection depends on ampacity, termination type, budget, and code requirements.

6. Do parallel runs reduce voltage drop?

Yes. Parallel conductors share current, reducing effective resistance and reactance per phase. That usually lowers voltage drop and power loss when the conductors are properly matched.

7. Is reactance always necessary?

Reactance matters most on longer runs, larger conductors, and lower power factors. For short feeders it may be modest, but including it improves three phase accuracy.

8. Can I use this result for final code compliance?

Use it for planning and checking, then verify against local electrical codes, installation conditions, cable data sheets, correction factors, and engineer approved design assumptions.