Definition

Noun: - A unit of apparent power in an alternating current (AC) circuit: A volt-ampere (VA) is a unit of measurement for apparent electrical power. It is equal to the product of the root-mean-square (RMS) voltage in volts and the RMS current in amperes in an AC circuit, without considering the phase difference between them.

Usage Examples

• Noun:
  • The transformer is rated at 500 volt-amperes to handle the load.
  • To size the uninterruptible power supply (UPS), you must calculate the total volt-ampere requirement of all connected devices.

Advanced Usage

• Distinction from Watt: The volt-ampere measures "apparent power," while the watt measures "real power." In AC circuits with reactive components (like motors or transformers), the current and voltage waveforms can be out of phase. The real power (watts) is the volt-ampere value multiplied by the power factor (a number between 0 and 1).
  • A device might draw 1000 volt-amperes but only consume 800 watts of real power, indicating a power factor of 0.8.

Variants and Related Words

• VA: The standard abbreviation for volt-ampere.
• Kilovolt-ampere (kVA): A unit equal to 1,000 volt-amperes, commonly used for larger equipment like generators and transformers.
  • The backup generator has a capacity of 50 kVA.

Synonyms

• Apparent power: This is the technical term for what the volt-ampere unit measures.

Noun

1. a unit of electrical power in an AC circuit equal to the power dissipated when 1 volt produces a current of 1 ampere