Calculator Inputs
Load Current Chart
Example Data Table
| Case | System | Voltage | Input | PF | Efficiency | Approx. Current |
|---|---|---|---|---|---|---|
| Office Lighting Panel | Single Phase | 230 V | 2.5 kW | 0.95 | 98% | 11.66 A |
| Workshop Motor | Three Phase | 415 V | 7.5 kW | 0.86 | 92% | 13.57 A |
| Battery Charging Bank | DC | 48 V | 1.2 kW | 1.00 | 94% | 26.60 A |
| Small HVAC Unit | Single Phase | 240 V | 3.8 kVA | 0.90 | 96% | 15.83 A |
Formula Used
DC load current: I = P / (V × η)
Single-phase AC load current: I = P / (V × PF × η)
Three-phase AC load current: I = P / (√3 × V × PF × η)
From apparent power, single-phase: I = S / V
From apparent power, three-phase: I = S / (√3 × V)
In these formulas, I is current in amperes, P is real power in watts, S is apparent power in volt-amperes, V is voltage, PF is power factor, and η is efficiency as a decimal. Demand and safety factors further adjust the design current.
How to Use This Calculator
- Select the system type: single-phase AC, three-phase AC, or DC.
- Choose whether you want to calculate from kW, W, kVA, VA, or a known current.
- Enter the operating voltage for the load.
- Type the power value or entered base current.
- Set power factor, efficiency, demand factor, and safety factor.
- Click Calculate Load Current to display results above the form.
- Review the current values, breaker estimate, and chart.
- Use the download buttons to save results in CSV or PDF format.
FAQs
1. What does load current mean?
Load current is the electrical current a device or circuit draws during operation. It helps engineers size conductors, protective devices, and power supplies more accurately.
2. Why is power factor important in AC calculations?
Power factor affects how much current an AC load needs for the same real power. Lower power factor increases current and can require larger cables and protection.
3. Why does three-phase current use √3?
Three-phase line calculations include √3 because line voltage and phase relationships differ from single-phase systems. It converts line values into the correct current relationship.
4. What is the difference between demand factor and safety factor?
Demand factor reduces current to expected simultaneous usage. Safety factor increases design current to provide installation margin and more conservative equipment selection.
5. Can I use this for breaker sizing?
This tool gives a practical breaker estimate, not a code decision. Final breaker size should follow local electrical standards, conductor limits, ambient conditions, and load characteristics.
6. Should efficiency be included for all loads?
Efficiency matters when input current is based on delivered output power. For direct apparent power entries, current already reflects input conditions more closely.
7. Is this calculator useful for DC systems?
Yes. DC current is calculated more simply because power factor is not used. The tool still lets you include efficiency, demand, and safety adjustments.
8. What voltage should I enter for three-phase systems?
Enter the line-to-line voltage commonly used in three-phase system design, such as 400 V or 415 V, unless your analysis specifically requires another value.