Kilovars

Kilovars (kVAr) are the unit of reactive power in alternating-current electrical systems. Reactive power accounts for the portion of electrical power that flows back and forth between source and load to sustain electric and magnetic fields; it does not perform useful work but is necessary for the operation of inductive devices such as motors and transformers. One kilovar equals 1000 volt-ampere reactive (VAR).

Reactive power is distinct from real power (kilowatts, kW) and apparent power (kilovolt-amperes, kVA). They relate through the power triangle: S^2 = P^2 + Q^2, with S in kVA, P in kW, and Q in kVAr. The power factor is cos(phi) = P/S, and Q = S sin(phi).

The sign of reactive power indicates load type: inductive loads produce positive Q, while capacitive loads produce negative Q.

Measurement and applications: Power meters measure kW, kVA, and kVAr to assess power quality and determine the need for correction. Utilities may impose penalties for low power factor. Capacitor banks or other devices can supply leading reactive power to improve the power factor, reducing currents and losses in feeders.

Kilovars are most relevant in industrial and distribution contexts with large inductive loads; understanding kVAr helps in sizing compensation equipment and designing efficient electrical systems. See also reactive power, power factor, capacitor bank.