kVA Calculator

Modern calculation of electrical rated power from current and voltage

Calculation

Rated Power Calculator

Calculate the rated power in kVA from the current in amperes and the voltage in volts. Choose between 1-phase and 3-phase calculation.

Result
Rated power:

Worth Knowing

What is kVA?

kVA (Kilovoltampere) is the unit for electrical apparent power. It indicates the product of voltage and current, regardless of the phase shift.

1-phase vs. 3-phase
1 Phase:
P = U × I
Household appliances
Lighting
3 Phases:
P = √3 × U × I
Industrial motors
Large consumers
Basic Formulas
1 Phase: \[P = U \times I\]
3 Phases: \[P = \sqrt{3} \times U \times I\]
√3 ≈ 1.732
Units

VA: Voltampere (apparent power)
kVA: Kilovoltampere (1 kVA = 1000 VA)
Difference to Watt: Does not consider phase shift

Rated Power Formulas

The rated power in VA (Voltampere) is calculated from the current and voltage. In 3-phase systems, the factor √3 is additionally considered, since three phases are offset by 120°.

1-Phase System

\[P_{VA} = U \times I\]
Example:

Given: U = 230V, I = 10A

\[P = 230 \times 10 = 2300\text{ VA} = \color{blue}{2.3\text{ kVA}}\]
Application:
  • Household appliances
  • Lighting
  • Small electrical devices
  • Single-phase motors

3-Phase System

\[P_{VA} = \sqrt{3} \times U \times I\]
Example:

Given: U = 230V, I = 10A

\[P = 1.732 \times 230 \times 10 = 3983.6\text{ VA} = \color{blue}{3.98\text{ kVA}}\]
Application:
  • Industrial motors
  • Large consumers
  • Three-phase machines
  • Industrial plants

Apparent Power vs. Active Power

Apparent Power (VA)

Definition: Product of voltage and current

\[S = U \times I\]

Use: Dimensioning of transformers, generators and cables

Active Power (W)

Definition: Actually consumed power

\[P = U \times I \times \cos(\phi)\]

Use: Energy consumption, electricity bill, heat generation

Practical Applications

Device/Application Voltage Current (approx.) Power (kVA) Phases
Household outlet 230V 16A 3.68 kVA 1
Electric stove 400V 16A 11.09 kVA 3
Small motor 400V 2A 1.39 kVA 3
Large motor (5kW) 400V 10A 6.93 kVA 3
Welding machine 400V 32A 22.18 kVA 3
Important Notes
  • In 3-phase systems, the voltage is usually the line-to-line voltage (e.g. 400V)
  • The factor √3 ≈ 1.732 applies to symmetrical 3-phase systems
  • The apparent power (VA) is always greater than or equal to the active power (W)
  • For purely resistive loads VA = W (cos φ = 1)
  • For inductive loads VA > W (cos φ < 1)
Dimensioning
Transformers:
• Design according to apparent power (kVA)
• Consider peak loads
• Include safety factor
Cables:
• Cross-section according to current
• Consider voltage drop
• Observe thermal load

Is this page helpful?            
Thank you for your feedback!

Sorry about that

How can we improve it?


Simple electrical functions

Watt from Ampere, Volt  •  VA from Ampere, Volt  •  Ampere from Watt, Volt  •  Speaker wire resistance  •