Formula Used
Wye voltage: VL = √3 × VPhase
Wye phase voltage: VPhase = VL / √3
Delta voltage: VL = VPhase
Apparent power: S = √3 × VL × I / 1000
Real power: P = √3 × VL × I × PF × efficiency / 1000
Current: I = P × 1000 / (√3 × VL × PF × efficiency)
Voltage drop: VD = √3 × I × (R cos φ + X sin φ) × length
Voltage unbalance: Unbalance% = maximum deviation from average / average × 100
How to Use This Calculator
Choose the calculation target first. Select wye or delta connection. Enter known voltage, current, power, power factor, and efficiency values. Add cable data if voltage drop is needed. Enter three measured line voltages for unbalance checking. Press calculate. The result appears above the form.
Example Data Table
| Case |
Connection |
VL |
I |
PF |
Main Result |
| Motor feeder |
Wye |
480 V |
25 A |
0.86 |
20.78 kVA, 17.87 kW |
| Panel check |
Wye |
415 V |
38 A |
0.90 |
27.32 kVA, 24.59 kW |
| Delta load |
Delta |
208 V |
18 A |
0.82 |
6.49 kVA, 5.32 kW |
| Unbalance check |
Measured |
481, 476, 484 V |
-- |
-- |
Average and unbalance percent |
Three Phase Voltage Calculation Guide
Three phase systems carry power through three alternating conductors. Each phase is separated by 120 electrical degrees. This spacing keeps total power smoother than a single phase supply. It also allows motors to start with better torque and less vibration.
Line Voltage And Phase Voltage
Line voltage is measured between two line conductors. Phase voltage is measured across one phase winding or one line and neutral point. In a wye connection, line voltage equals phase voltage multiplied by the square root of three. In a delta connection, line voltage equals phase voltage. This difference is important when selecting insulation, drives, breakers, and transformer taps.
Power, Current, And Power Factor
Three phase power uses voltage, current, and power factor together. Apparent power is measured in kVA. Real power is measured in kW. Reactive power is measured in kVAr. A low power factor increases current for the same useful load. Higher current may raise cable loss, heat, and voltage drop.
Voltage Drop And Unbalance
Long conductors create voltage drop. The calculator estimates drop from current, cable length, resistance, reactance, and load power factor. It then shows the percentage drop against line voltage. Voltage unbalance compares the average of three line readings with the largest deviation. Even small unbalance can heat three phase motors. Check supply terminals before blaming equipment.
Engineering Use
This tool is useful for panels, pumps, compressors, heaters, generators, and transformer checks. It supports wye and delta relationships. It can solve missing voltage, current, kVA, or kW when enough data is entered. It also gives phase impedance when phase voltage and current are available. Use nameplate values for planning. Use measured values for troubleshooting.
Good Practice
Always confirm units before entering data. Enter line voltage as volts between phases. Enter current as line current in amperes. Use decimal power factor, such as 0.85. Enter efficiency as a decimal when motor output power is used. Keep records with the export buttons. Compare results with local codes and manufacturer data before final design.
Document every assumption in the report. Note ambient conditions, cable routing, load type, and duty cycle. These notes make later maintenance easier. They also help reviewers spot unsafe margins before final installation approval.
FAQs
What is three phase line voltage?
Line voltage is the voltage measured between any two line conductors. It is commonly used for panel ratings, motor nameplates, breaker selection, and feeder calculations.
What is phase voltage in a wye system?
In a wye system, phase voltage is measured from line to neutral. It equals line voltage divided by the square root of three.
Is delta phase voltage different from line voltage?
No. In a delta connection, each phase winding is connected across two lines. Therefore phase voltage and line voltage are the same.
How do I calculate three phase current?
Use current equals power times 1000 divided by square root of three, line voltage, power factor, and efficiency. Use kW for power.
Why is power factor important?
Power factor shows how effectively current produces real work. Lower power factor increases current, cable heating, voltage drop, and apparent power demand.
What is acceptable voltage unbalance?
Many motor applications prefer very low unbalance. Even small unbalance can increase motor heating. Always compare with equipment limits and local standards.
Can this calculator estimate voltage drop?
Yes. Enter current, length, resistance, reactance, line voltage, and power factor. The calculator estimates voltage drop and percentage drop.
Can I export the calculation?
Yes. After pressing calculate, use the CSV or PDF buttons. They download the current result, formulas, and notes.