# Volt amperes

Physical unit
Unit name Volt amperes
Unit symbol ${\ displaystyle \ mathrm {VA}}$ Physical quantity (s) Apparent power
Formula symbol ${\ displaystyle S}$ dimension ${\ displaystyle {\ mathsf {M \; L ^ {2} \; T ^ {- 3}}}}$ system International system of units
In SI units ${\ displaystyle \ mathrm {1 \, VA = 1 \, V \ cdot 1 \, A = 1 \, W}}$ Named after Alessandro Volta , André-Marie Ampère

The volt-ampere with the symbol VA is a legal unit of measurement for the apparent electrical power . It is used for alternating quantities ( alternating voltage , alternating current , also three-phase alternating current ) in electrical power engineering to identify the connected load of electrical machines (such as three-phase motors ) or transformers . ${\ displaystyle S}$ The watt is the general unit of measurement for the physical quantity of power . Volt-amperes for apparent electrical power and Var for reactive electrical power are used as special units (DIN 1301, DIN 1304, DIN 40110).

The unit of apparent power is linked to SI units according to

${\ displaystyle \ left [S \ right] = {\ left [U _ {\ mathrm {eff}} \ right]} _ {\ text {SI}} \ cdot {\ left [I _ {\ mathrm {eff}} \ right]} _ {\ text {SI}} \ to 1 \, \ mathrm {VA} = 1 \, \ mathrm {V} \ cdot 1 \, \ mathrm {A} = 1 \, \ mathrm {W}}$ .

As is usual with units of measurement , prefixes for units of measurement are used to achieve manageable numerical values , such as "kVA" for "kilovolt ampere" (= 1,000 VA) or "MVA" for "megavolt ampere" (= 1,000,000 VA).

## literature

• Karl Küpfmüller, Wolfgang Mathis, Albrecht Reibiger: Theoretical electrical engineering: An introduction . 18th edition. Springer, Berlin, Heidelberg 2008, ISBN 978-3-540-78589-7 .