
LINE REACTORS
What are AC Line Reactors… An INTRODUCTION:
The Line Reactors are also called as Line Chokes or Inductors; Line reactors are electromagnetic devices which consist of a steel core electrical grade laminations and copper inductor coils. The coil forms a magnetic field as current flows through it, which limits the rate of rise of current.
Reactors are classified as Line (Input) Reactors and Load (Output) reactors.
Line Reactors – connected between AC Line Source and the input of a Variable Frequency Drive (VFD) and protects the drive from tripping nuisance and damages.
Load Reactors on the other hand are used at the load side of a VFD to protect motors if the wiring distance between the VFD and motor is very long (over 100 feet).
BENEFITS OF Line Reactors:
– Impedance at 2%, 3%,4%,5% – Low ripple & Limits inrush Currents – Protection of motor drive electronics – Reduction of main harmonics levels to ~35% – Increased System Performance and Reliability – Improves power factor & Mitigates voltage distortion – Prevention from nuisance tripping caused by power line voltage spikes |

Difference between AC Line Reactors, AC Load Reactors & DC Line/Link Chokes in VFD
- AC Line reactor – installed before the VFD, protects the drive
- AC Load reactor – installed after the VFD, protects the motor
- DC Link reactor – inserted into the DC link of a drive
A Reactor at the Input to reduce Harmonics
WITH NO REACTOR – the three-phase input current may contain as much as 85% or more total harmonic distortion.
WITH AC LINE REACTOR – the peaks of the line current are reduced and somewhat broadened out.
What is Impedance?
Resistance in ohms but also commonly referenced in terms of percent when combined with the system voltage and line current flowing through the reactor.

Line reactors are classified by their percent impedance (denoted as IZ%) which is the voltage drop due to impedance at the rated current expressed as a percent of rated voltage
- 2% Impedance – Line Reactors are usually sufficient to absorb power line spikes and motor current surges. They prevent nuisance tripping of drives or circuit breakers in most applications
- 4% impedance – Line Reactors are best for reducing harmonic currents and frequencies. Use them when you must comply with IEEE 519.
- When higher line disturbances are present 5% impedance reactors may be needed.
- Higher impedance reactor can be used to reduce harmonics even further when the aim is to diminish noise from the motor or to extend motor life