Single-Phase vs Three-Phase Power Basics
When this applies
Use this guide when you need fast clarity on balanced three-phase power relationships and where simplified formulas are valid.
Tool to use
Balanced three-phase P, S, and |Q| from line quantities and cos φ.
Open Three-Phase Power Calculator →Steps
- 1Identify the measurement basis: line-to-line voltage and line current for balanced three-phase.
- 2Compute apparent power with S = sqrt(3)*V_LL*I_L.
- 3Compute real power with P = S*cos(phi) and derive reactive magnitude from the power triangle.
- 4State whether values are per-phase or total-system quantities.
- 5Use full phasor and unbalance analysis if system asymmetry is material.
Examples
- Sanity-checking panel loading assumptions during early facility planning.
- Comparing apparent vs real power impact at different power factors.
What to avoid
- Mixing phase and line quantities in one formula.
- Treating cos(phi) as a signed reactive-direction indicator.
- Using balanced formulas for strongly unbalanced loads.
Related tools
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Browse all task guides or see the full list on the Generators & Calculators hub.
FAQ
Does this tell me if loads are leading or lagging?
No. The basic calculator reports reactive magnitude, not sign from full phasor context.
Can I use this for harmonics-heavy systems?
Not as final analysis; harmonics require true power-quality methods.