In order to keep the VFDs protected, businesses may consider installing a line reactor on the input side of the system.
What is a Line Reactor?
A line reactor is a heavy-duty inductor that is designed to absorb short, high-voltage transients that originate from local grids. The electromagnetic unit features a steel or iron core with copper coils. During use, a magnetic field is generated, facilitating current flow. This action limits the rate of current rise. Line reactors can be AC or DC. AC line reactors with 3% or 5% impedance are standard units installed between the power source and the VFD. Line reactors with 3% impedance are suitable for solid-state drives in North America, while units with 5% impedance are used in facilities requiring a higher degree of protection from power disturbances – usually in locations outside of North America. Next, a DC link reactor is a type of line reactor installed in the DC link of the VFD.
For best results, the unit should be secured close to the drive. Moreover, in facilities that utilize several VFDs, a single line reactor per drive should be setup for maximum protection. It is important to highlight that protection is only for the input side or the drive (though its benefits can extend to connected motors). For output protection (motor), a load reactor can be applied to the system.
When to Use a Line Reactor
Businesses that use VFDs to support heavy machinery or sensitive equipment may use line reactors to add an extra layer of protection on the input side of the system. Facilities with power sources that are known to cause voltage spikes or drops, surges, tripping, harmonics (IEEE-519, “Harmonic Control in Electrical Power Systems”) and other forms of power disturbances should consider installing the device. Additionally, a line reactor is recommended for systems that are connected to a supply transformer with a kVA rating that is greater than 10x the kVA rating of the VFD.