Power Calculator

Electrical power is the rate at which electrical energy is transferred or converted, measured in watts (W). Understanding power calculations is fundamental for system sizing, equipment selection, energy cost analysis, and safety assessment in electrical engineering.

DC vs AC Power: In DC circuits, power is simply $P = V \times I$, with all power performing useful work. AC circuits have three power components: real power (watts) that does work, reactive power (VAR) for magnetic fields, and apparent power (VA) that equipment must handle. The power triangle relates these: $S^2 = P^2 + Q^2$, where power factor (PF) = $P/S$ determines efficiency.

Why It Matters: Power calculations determine equipment ratings (transformers, cables, breakers), predict energy costs (kWh consumption plus demand charges), ensure safety (managing $I^2R$ heat dissipation), and identify efficiency improvements. A 100kW load at 0.8 PF requires 125kVA capacity—25% more infrastructure than ideal.

Load Characteristics: Resistive loads (heaters, incandescent lights) have $PF = 1.0$ with $P = V^2/R$. Inductive loads (motors, transformers) have $PF < 1.0$ with lagging current. Capacitive loads provide power factor correction. Nonlinear loads (VFDs, LED drivers) create harmonics requiring special analysis.

Three-Phase Systems: Industrial standard delivering $\sqrt{3}$ (1.732) times more power than single-phase for the same current. Power is constant rather than pulsating. Common voltages: 208V, 400V, 480V line-to-line. Formula: $P = \sqrt{3} \times V_{L} \times I_{L} \times PF$ for balanced loads.

Standards Reference: IEEE 141 for industrial power systems, IEC 60038 for standard voltages, NEC Article 220 for load calculations.