Input Section
Use the responsive 3-column, 2-column, and 1-column layout across screens.
Formula Used
I = P × 1000 ÷ (V × PF × η)
I = P × 1000 ÷ (√3 × VL × PF × η)
I = S × 1000 ÷ V
I = S × 1000 ÷ (√3 × VL)
Star: IL = IPh
Delta: IL = √3 × IPh
How to Use This Calculator
- Select the calculation mode that matches your project data.
- Choose the connection type for three-phase systems.
- Enter voltage, power, power factor, efficiency, or phase current.
- Set a safety factor for breaker and feeder review.
- Press the calculate button to show the result above the form.
- Review line current, phase current, apparent power, and breaker suggestions.
- Use the CSV and PDF buttons to export the result summary.
- Study the graph to see current sensitivity versus voltage or phase current.
Example Data Table
| Scenario | Method | Voltage (V) | Power / kVA | PF | Efficiency (%) | Current (A) |
|---|---|---|---|---|---|---|
| Lighting feeder | Single-phase real power | 230 | 2.40 kW | 1.00 | 100 | 10.43 |
| Air compressor | Single-phase real power | 240 | 3.20 kW | 0.88 | 92 | 16.47 |
| Process pump | Three-phase real power | 400 | 15.00 kW | 0.86 | 94 | 26.78 |
| Ventilation fan | Three-phase real power | 415 | 22.00 kW | 0.90 | 95 | 35.80 |
| Distribution panel | Three-phase apparent power | 480 | 75.00 kVA | 0.92 | 98 | 90.21 |
Frequently Asked Questions
1. What is line current?
Line current is the current flowing through each supply conductor. In three-phase systems, it may differ from phase current depending on whether the connection is star or delta.
2. When should I use the real power method?
Use the real power method when you know the load power in kilowatts and also have power factor and efficiency. This is common for motors, pumps, fans, and driven equipment.
3. When should I use the apparent power method?
Use the apparent power method when transformer, feeder, or panel demand is already stated in kVA. It gives current directly from voltage without needing power factor for the current formula.
4. Why does delta connection change phase current?
In a delta circuit, line current is √3 times the phase current. In a star circuit, line current equals phase current. This relation is essential for winding and conductor checks.
5. Does this calculator size cables automatically?
No. It estimates current and a breaker target only. Final cable sizing still needs insulation method, ambient temperature, grouping, allowable voltage drop, and local code review.
6. Why is efficiency included?
Efficiency converts useful output power into required electrical input power. Lower efficiency means more input power is needed, which increases the line current for the same output load.
7. Why does current drop when voltage rises?
For a fixed power demand, higher voltage means the same power can be delivered with less current. That is why the graph slopes downward in power-based calculation modes.
8. Can I use a safety factor above 1.25?
Yes. A higher factor can be useful for conservative planning or special loading conditions. However, final protection settings should still follow equipment data and your applicable electrical standard.
Design Notes
This page uses a white theme and keeps all main sections in one vertical flow. The form itself changes to three columns on large screens, two on medium screens, and one on mobile.