VTdrive What is VFD Line Reactor0 pages
WHAT IS A LINE REACTOR?
A 3-phase 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.
Transformer
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Line Reactor (XJ
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Line Current
Loads
Line Reactors are current-limiting 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 (XL) and is calculated as follows:
XL = 2 TT 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 (uH)
-Hx10-6
By inspection of the XL 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 (R-ohms) is very low by design so that the
power losses (watts-l2R) are low.
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