Blind work

The reactive energy or reactive energy is a term of electrical engineering at one with AC it converts supplied electric consumers, the more electrical energy concerns as into useful energy. This occurs when it builds up an electrostatic or electromagnetic field, storing energy and then sending it back to the electricity supplier.

Its symbol is The unit is the var second with the unit symbol vars , the kilovar hour kvarh is preferably used, which corresponds to the kilowatt hour for active energy. ${\ displaystyle W_ {b} {\ text {or}} W_ {Q} \ ,, \; W_ {q} \ ,, \; E_ {b} \ ,, \; E_ {Q} \ ,, \; E_ {q} \ ,.}$

In the case of sinusoidal electrical voltage and current intensity with the period duration or in the case of the displacement reactive power, the (displacement) reactive work transported in the time span is defined by ${\ displaystyle u (t)}$ ${\ displaystyle i (t)}$ ${\ displaystyle T}$ ${\ displaystyle Q}$ ${\ displaystyle t_ {2} -t_ {1}}$

{\ displaystyle W_ {b} = \ int \ limits _ {t_ {1}} ^ {t_ {2}} u \ left (t - {\ frac {T} {4}} \ right) \ i (t) \ \ mathrm {d} t = Q \ cdot (t_ {2} -t_ {1}) \ ,.}

Reactive work is connected to reactive current . Since this loads the supply networks of the network operators without the end customer being supplied with useful energy, it is undesirable. With most electricity supply contracts, certain limits for the maximum reactive power drawn must be adhered to, otherwise higher network usage fees have to be paid. For this purpose, the reactive energy for large-scale customers is measured with special energy meters and, if the permitted limits are exceeded, the excess is charged. Exceeding the permissible displacement reactive power can be counteracted by using systems for reactive power compensation .

In the case of sine values, the active factor , reactive power and active power are in a fixed relationship . ${\ displaystyle \ cos \ varphi}$ ${\ displaystyle Q}$ ${\ displaystyle P}$ ${\ displaystyle \ tan \ varphi = Q / P}$

Examples:

The active factor is greater than 99% if the reactive power is less than 14% of the active power.
The active factor is greater than 93% if the reactive power is less than 39% of the active power.
The active factor is greater than 90% if the reactive power is less than 48% of the active power.

Individual evidence

↑ DIN 40110-1: 1994: "Alternating current quantities"

literature

Réne Flosdorff, Günther Hilgarth: Electrical energy distribution . 4th edition. BG Teubner, 1982, ISBN 3-519-36411-5 .
Günter Springer: Expertise in electrical engineering . 18th edition. Europa-Lehrmittel, Wuppertal 1989, ISBN 3-8085-3018-9 .

[1] DIN 40110-1: 1994: "Alternating current quantities"