Three Phase Electrical Load Calculator
Calculate Active Power (kW), Apparent Power (kVA), and Reactive Power (kVAR) for three-phase systems.
Calculation Results
Understanding Three-Phase Load Calculations
Three-phase electrical systems are the standard for power distribution and industrial equipment worldwide. Calculating the load accurately is critical for sizing circuit breakers, conductors, and transformers correctly.
The Three-Phase Power Formula
In a balanced three-phase system, the total power is not simply voltage multiplied by current. We must account for the square root of three (approximately 1.732) because the phases are offset by 120 degrees.
- VL-L: Line-to-Line Voltage.
- I: Current in Amperes (per phase).
- PF: Power Factor (the ratio of real power to apparent power).
- √3: Constant for 3-phase systems (approx. 1.732).
Real, Apparent, and Reactive Power
When dealing with AC (Alternating Current) three-phase loads, there are three types of power to consider:
- Real Power (kW): The actual work being performed (heat, motion).
- Apparent Power (kVA): The total power flowing through the circuit. This is what you size your wires and transformers for.
- Reactive Power (kVAR): Power that bounces back and forth between the source and load (stored in magnetic or electric fields).
Practical Example
Imagine an industrial motor running on a 480V three-phase supply. If the motor draws 50 Amps and has a power factor of 0.85, the calculation would be:
Calculation: 1.732 × 480V × 50A × 0.85 = 35,332 Watts or 35.33 kW.
The apparent power (kVA) would be: 1.732 × 480V × 50A = 41,568 VA or 41.57 kVA.
Why the Power Factor Matters
A low power factor means you are drawing more current than necessary to do the same amount of work. This leads to inefficiency and potentially higher utility costs. Most industrial facilities aim for a power factor above 0.90 or 0.95.