Line reactors are commonly used in adjustable speed drive
applications to improve power quality. They are connected in series with the input
terminals of the drive to serve multiple functions.
1) suppress
voltage transients enabling drives with a dc bus capacitor to ride thru some
system voltage disturbances, minimize O/V nuisance tripping, protect diodes
from transients, protect dc bus capacitor,
2) Increase
effective input impedance resulting in lower drive input harmonic current
distortion and system voltage distortion, reduce true rms current, improve
total (true) power factor.
5% effective impedance (at full
load) yields about 35% THD-I, 3% impedance at full load results in about 45%
THD-i. Note: a drive system with a 5% impedance line reactor, operating at 60%
of reactor current rating will look like a 3% impedance reactor.
