Calculator
Choose what to solve, enter known electrical values, then include efficiency, demand, runtime, and energy cost for a broader site power review.
Example Data Table
These sample rows show typical balanced site loads. Values are illustrative for estimating construction power demand and reviewing likely operating ranges.
| Equipment | Connection | Line Voltage (V) | Line Current (A) | Power Factor | Efficiency (%) | Input Power (kW) | Output Power (kW) |
|---|---|---|---|---|---|---|---|
| Tower crane | Wye | 415 | 68 | 0.86 | 92 | 42.03 | 38.67 |
| Dewatering pump | Delta | 415 | 32 | 0.82 | 88 | 18.86 | 16.60 |
| Concrete mixer | Wye | 400 | 24 | 0.80 | 90 | 13.30 | 11.97 |
| Material hoist | Delta | 480 | 54 | 0.89 | 93 | 39.96 | 37.16 |
Formula Used
S (kVA) = √3 × VL × IL ÷ 1000
Pin (kW) = S × PF
Q (kVAR) = √(S² − Pin²)
Pout (kW) = Pin × Efficiency
IL = Pin × 1000 ÷ (√3 × VL × PF)
VL = S × 1000 ÷ (√3 × IL)
Wye: Vphase = VL ÷ √3, Iphase = IL
Delta: Vphase = VL, Iphase = IL ÷ √3
Demand kW = Pin × Demand Factor
Monthly kWh = Demand kW × Hours/Day × Days/Month
How to Use This Calculator
- Select whether you want to solve for power, current, or voltage.
- Choose the connection type as wye or delta.
- Enter known line values using the correct unit selectors.
- Set power factor and efficiency for the connected equipment.
- Add demand factor, operating hours, and energy rate if cost review matters.
- Click Calculate to show results above the form.
- Review the graph, then export the report as CSV or PDF.
FAQs
1. What formula does this calculator use?
It uses the balanced three-phase relation S = √3 × V × I. Real power equals apparent power multiplied by power factor. Output power applies efficiency, and energy cost uses runtime plus demand-adjusted kilowatt input.
2. Should I enter line voltage or phase voltage?
Enter line-to-line voltage. The calculator then derives phase voltage automatically from the selected connection. This keeps feeder, service, and equipment checks aligned with common construction distribution practice.
3. Why does a lower power factor increase current?
For the same real power, a lower power factor means more apparent power is needed. That raises line current, which can increase voltage drop, losses, and equipment sizing requirements.
4. What is the difference between wye and delta here?
The total three-phase power formula stays the same, but phase voltage and phase current change. Wye divides line voltage by √3. Delta divides line current by √3.
5. Why does the calculator ask for efficiency?
Efficiency separates electrical input from useful output. This matters for motors, pumps, hoists, and mixers because equipment output is always lower than electrical power entering the machine.
6. What does demand factor change?
Demand factor reduces input power to a more realistic operating level. It helps estimate site diversity, monthly energy use, and budget exposure when all connected equipment does not run fully at once.
7. Can this calculator size breakers or feeders?
It provides a minimum feeder ampacity using 125% of line current for a quick planning check. Final conductor, breaker, and protection sizing still need code review and local design criteria.
8. Is this suitable for unbalanced systems?
No. It assumes a balanced three-phase load. For unbalanced panels, mixed single-phase circuits, or harmonic-heavy systems, use phase-by-phase analysis and a fuller distribution study.