KVA Calculator
Free calculate apparent power in kilovolt-amperes (kva) from voltage and current for single-phase and three-phase systems.
Input Parameters
Line-to-line for three-phase, line-to-neutral for single-phase
Results
Enter values to calculate
What is KVA?
KVA (kilovolt-amperes) is a unit of apparent power in AC electrical systems. It represents the product of voltage and current, regardless of the phase relationship between them.
Apparent power (kVA) is different from real power (kW). Real power is the actual power consumed, while apparent power includes both real power and reactive power. The ratio is the power factor: PF = kW/kVA.
KVA is crucial for sizing transformers, generators, and electrical equipment. Equipment must be rated for apparent power, not just real power, to handle the total current flow.
KVA Formulas
Single-Phase
Three-Phase
How to Calculate KVA
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1
Identify system type
Determine if it's single-phase or three-phase.
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2
Measure voltage and current
For three-phase, use line-to-line voltage. For single-phase, use line-to-neutral voltage.
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3
Apply the formula
Single-phase: kVA = (V×I)/1000. Three-phase: kVA = (√3×V×I)/1000.
Practical Examples
Example 1: Single-Phase
A single-phase system has 240 V and 20 A. Calculate kVA.
Solution:
kVA = (V × I) / 1000 = (240 V × 20 A) / 1000
kVA = 4.8 kVA
Example 2: Three-Phase
A three-phase system has 480 V line-to-line and 50 A. Calculate kVA.
Solution:
kVA = (√3 × V × I) / 1000 = (1.732 × 480 × 50) / 1000
kVA = 41.57 kVA
Applications
Transformer Sizing
Determining the required kVA rating for transformers to handle the load's apparent power requirements.
Generator Selection
Sizing generators and backup power systems based on total apparent power demand.
Electrical Design
Calculating total load, sizing conductors, and designing electrical distribution systems.
Power Factor Correction
Understanding the relationship between kVA (apparent), kW (real), and kVAR (reactive) power.
Frequently Asked Questions
What is the difference between kVA and kW?
kVA is apparent power (V×I), while kW is real power (actual work done). kW = kVA × power factor. For resistive loads (PF=1), kVA = kW.
Why is √3 used for three-phase?
In three-phase systems, the line-to-line voltage is √3 times the line-to-neutral voltage. The √3 factor accounts for the 120° phase difference between phases.
What is power factor?
Power factor (PF) = kW/kVA, ranging from 0 to 1. It represents the ratio of real power to apparent power. PF < 1 indicates reactive power (inductive or capacitive loads).
Why size equipment by kVA, not kW?
Equipment must handle the total current (determined by kVA), not just the real power. Transformers and generators are rated in kVA to account for both real and reactive power.
How do I convert kVA to amperage?
For single-phase: I = (kVA × 1000) / V. For three-phase: I = (kVA × 1000) / (√3 × V). This gives the current for a given apparent power.