What is the difference between real, reactive, and apparent power?

Real power (W/kW) does useful work. Reactive power (VAR/kVAR) oscillates between source and load (inductors/capacitors), doing no net work but requiring current. Apparent power (VA/kVA) = magnitude of complex power S = P + jQ.

Why do motors have low power factor?

Induction motors draw lagging reactive current for magnetizing the stator core. At full load PF ≈ 0.85-0.90. At partial load PF drops to 0.5-0.7. This requires oversized transformers and cables.

What power factor do utilities require?

Most utilities require PF ≥ 0.85 lagging, some require 0.90-0.95. Below threshold, reactive energy surcharges apply (typically £0.01-0.03/kVARh). Large industrial facilities pay significant penalties for low PF.

AC Power Calculator (Real, Reactive, Apparent)

Calculate real power P = V·I·cosφ (kW), reactive power Q = V·I·sinφ (kVAR), apparent power S = V·I (kVA). Power triangle: S² = P² + Q². Power factor PF = P/S = cosφ.

2D stress state at a point. All stresses in MPa.

σx — Normal Stress X (MPa)

σy — Normal Stress Y (MPa)

τxy — Shear Stress (MPa)

⚙ Mechanical Note: Results are based on standard textbook formulas and ISO/AASHTO references. Always verify critical designs with applicable codes (ISO 898, AASHTO 1993, AISC, Eurocode 3) and a qualified engineer.

How to Use

Enter the values for the patient or scenario you are assessing. Calculate real power P = V·I·cosφ (kW), reactive power Q = V·I·sinφ (kVAR), apparent power S = V·I (kVA). Power triangle: S² = P² + Q². Power factor PF = P/S = cosφ. Use the ac power result to inform your clinical assessment.

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AC Power Calculator (Real, Reactive, Apparent)

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Frequently Asked Questions

What is the difference between real, reactive, and apparent power?

Why do motors have low power factor?

What power factor do utilities require?