WHAT IS A LINE REACTOR?
A 3phase Line Reactor is a set of three (3) coils (also known as windings, chokes or inductors) in one assembly. It is a series device, which means it is connected in the supply line such that all line current flows through the reactor, as shown below.
Line Reactors are currentlimiting devices and oppose rapid changes in current because of their impedance. They hold down any spikes of current and limit any peak currents. This resistance to change is measured in ohms as the Line Reactor's AC impedance (X_{L}) and is calculated as follows:
X_{L} = 2 π f L (ohms), where:
f = frequency
harmonic frequency examples:
Harmonic (60 Hz)

Frequency (Hz)

5th

300

7th

420

11th

660

L = reactor inductancein henries (H), millihenries (mH)  H x 10^{3}, microhenries (µH)  H x 10^{6}
By inspection of the X_{L} formula, the Line Reactor is directly proportional to the frequency (f) and the inductance (L). That is, if the impedance of a Line Reactor is 10 ohms at 60 Hz, then at the 5th harmonic (300 Hz) the impedance is 50 ohms. If the inductance (L) is increased, then the impedance will increase proportionally.
This increase in Line Reactor impedance will reduce the current in the line. The higher the frequency (Hertz), the lower the current. A Line Reactor's DC resistance (Rohms) is very low by design so that the power losses (wattsI^{2}R) are low.
Line Reactors are rated by % impedance, voltage and current. However, they are sized by % impedance, voltage and motor horsepower. The motor horsepower determines the necessary current rating for the Line Reactor.
Line Reactors are rated by impedance, voltage and current.
 Impedance (% impedance of load Z)
The load impedance (Z) is calculated by this formula:
Z = V/I, whereZ = load impedance(ohms), V = line voltage(volts), andI = line current(amps)
This percent of load impedance also determines the voltage drop across the Line Reactor. For example, a 5% Line Reactor would have a 5% voltage drop.
 Voltage rating
Since a Line Reactor is a currentsensitive device, the voltage rating is needed for dielectric concerns as a maximum voltage and horsepower. It is also used to determine the current rating when given only voltage and horsepower.
 Current rating (amperes)
This is the current required by the load(s). It is total current flowing to the load(s) and through the reactor. This current is measured in amperes (amps).