Enter Electrical Values
Use current mode for readings. Use known power mode for nameplate values.
Example Data Table
| Input | Example value | Purpose |
|---|---|---|
| Three phase line voltage | 415 V | Supply line-to-line voltage |
| Three phase line current | 12 A | Measured balanced line current |
| Source power factor | 0.85 | Converts apparent power into real power |
| Demand factor | 90% | Allows for expected operating load |
| Conversion efficiency | 95% | Allows for estimated system losses |
| Target single phase voltage | 230 V | Used for equivalent current |
| Target single phase power factor | 0.90 | Used for output apparent power |
Formula Used
The calculator uses balanced three phase relationships. Voltage is line-to-line voltage. Current is line current.
S is apparent power in VA. P is real power in W. PF, demand factor, and efficiency use decimal values in the formulas.
How to Use This Calculator
- Choose the input method that matches your available electrical data.
- Enter line-to-line voltage and either current or known three phase power.
- Enter realistic power factor, demand, and efficiency values.
- Enter the planned single phase voltage and expected power factor.
- Set a breaker margin and daily operating hours.
- Press the calculation button and review the result above the form.
- Use the export buttons to retain a planning summary.
Planning Three Phase and Single Phase Power
Three Phase and Single Phase Power
Three phase systems are common in workshops, factories, and large buildings. Single phase circuits serve many smaller tools, appliances, and control loads. A conversion calculation helps compare these supply arrangements. It does not replace approved electrical design. It gives a practical estimate before selecting equipment.
Reading the Input Values
The calculator begins with line-to-line voltage and line current. For balanced three phase loads, apparent power uses the square root of three. Real power also uses the power factor. Power factor shows how effectively current becomes useful work. Motors, transformers, and inductive loads often have lower power factors.
Allowing for Demand and Losses
Demand factor adjusts the result for expected operating load. A motor may not run at its full rating all day. Efficiency then estimates losses in conversion equipment, cables, and transformers. The remaining real power becomes the usable single phase output estimate. Use conservative values where load information is uncertain.
Current and Protection Planning
The selected single phase voltage determines equivalent current. Lower voltage requires more current for the same power. Higher current needs larger conductors, breakers, and connectors. The calculator also applies a configurable breaker margin. Local rules, ambient temperature, installation method, and motor starting current can change the final choice.
Checking Phase Balance
Balanced current is an important assumption. Three phase systems can become unbalanced. Uneven phase loading may cause neutral current, voltage drop, overheating, or poor motor performance. Do not use a single calculated result to ignore a measured imbalance. Correct serious imbalance before adding more loads.
Choosing the Right Method
Use known power mode when a nameplate gives kW, kVA, VA, or watts. Use voltage and current mode when meter readings are available. Enter the correct power factor for apparent-power inputs. Confirm whether the stated voltage is line-to-line. Most three phase nameplates use line voltage. Do not enter phase-to-neutral voltage unless the equipment documentation requires it.
Using the Result Safely
The output supports budgeting, preliminary sizing, and simple comparisons. It cannot make a three phase motor run directly from a single phase supply. That task may need a properly rated variable-frequency drive, phase converter, or replacement motor. Sensitive equipment also needs compatible voltage, frequency, grounding, and protection. Ask a qualified electrician to review final installation choices. Keep measurements, nameplate data, and calculated assumptions with the project records.
Final Circuit Checks
Before using any calculated amperage, inspect the full circuit path. Check supply capacity, conductor insulation, terminal ratings, disconnects, and earthing arrangements. Consider voltage drop across long cable runs. Consider harmonics when electronic drives or rectifiers are present. Provide separate allowance for startup current where motors, compressors, or pumps are involved. Record the assumptions used in the estimate. Clear records make later checks faster and reduce avoidable changes during installation. Confirm supply limits, generator ratings, and duty cycles before relying fully on it.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates usable single phase power, apparent power, current, daily energy, and a planning breaker value from three phase data. It assumes a balanced source and the stated input conditions.
2. Why is the square root of three used?
Balanced three phase apparent power uses √3 × line voltage × line current. The relationship reflects the phase displacement between the three conductors in a balanced system.
3. What is the difference between kW and kVA?
kW is real power that performs useful work. kVA is apparent power. Power factor links them. For a given kVA value, lower power factor produces lower kW.
4. Which voltage should I enter?
Enter the three phase line-to-line voltage. This is often the value printed on equipment nameplates. Use the target single phase voltage for the output side.
5. Can this run a three phase motor from single phase?
No. The calculation compares equivalent power and current. Running a three phase motor from single phase normally needs suitable conversion equipment or a replacement motor.
6. What efficiency should I use?
Use the documented efficiency of the converter or transformer when available. For early planning, choose a conservative estimate and confirm it with the equipment manufacturer.
7. What does demand factor change?
Demand factor reduces the calculation to expected operating load. It is useful when connected equipment is not expected to run at full output at the same time.
8. Is the suggested breaker rating final?
No. It is a planning reference only. Final breaker selection also depends on cable rating, load type, startup current, coordination, installation method, and local electrical requirements.
9. Can I use unbalanced measurements?
Use separate measurements and professional review for unbalanced systems. This calculator uses a balanced-load assumption, so one average current value can hide a serious phase imbalance.
10. Why does lower single phase voltage increase current?
Power equals voltage times current times power factor. When required power stays constant, a lower voltage needs more current to deliver the same output.
11. Should I install equipment using this result alone?
Always verify local rules before installing any electrical equipment.