An electrical reactor is an inductor designed to add impedance to an AC circuit. By resisting changes in current, it can help limit current, reduce the effect of electrical disturbances, or moderate voltage changes, depending on where it is installed. A line reactor is installed on the input side of a variable frequency drive (VFD), while a load reactor is installed between the drive and its motor. The right choice depends primarily on whether the concern is the incoming power supply or the drive’s output cable and motor circuit.
Click here to get more.
An electrical reactor is a passive inductive component, typically made with a winding around a magnetic core. Its inductance opposes changes in current, and its effect depends on the circuit’s frequency, current, and system configuration. Reactors are used in power systems and motor-drive applications for functions such as current limiting, filtering, and controlling electrical transients.
In a VFD installation, a reactor adds impedance at a selected point in the circuit. On the input side, it can help moderate current changes associated with disturbances or drive operation; on the output side, it can help reduce the severity of voltage transitions reaching the motor. A reactor is not the same as a harmonic filter, surge protector, or dv/dt filter, even though it may contribute to system-level mitigation.
Performance depends on the reactor’s electrical rating and the surrounding equipment. For example, a common design reference is 3% impedance, but that value is not appropriate for every drive or application. The manufacturer’s recommendations and the system design should determine the required impedance, current rating, and thermal capacity.
The main difference is their location and the side of the drive they address. A line reactor is connected between the power source and the VFD input. A load reactor, also called an output reactor, is connected between the VFD output and the motor.
| Comparison point | Line reactor | Load reactor |
|---|---|---|
| Installation location | Supply side of the VFD | Output side, between VFD and motor |
| Primary focus | Incoming power and drive input current | Drive output waveform, motor cable, and motor circuit |
| Typical evaluation reason | Supply disturbances, current peaks, or input-side considerations | Long motor leads or concerns about output voltage transitions |
| Does it replace the other type? | No; it addresses a different circuit location | No; it addresses a different circuit location |
Consider a line reactor when the project calls for additional impedance at the VFD input. This may be relevant where the supply is subject to disturbances, where drive input current needs to be considered, or where the drive manufacturer recommends an input reactor. It may also be used as one part of a broader power-quality strategy, but its effect should not be confused with a guaranteed reduction in all harmonics or protection against every transient.
Check the supply voltage, phase configuration, rated input current, available fault current, and installation environment before specifying one. Line reactors are designed for the system’s operating conditions, including its supply frequency; common industrial supply frequencies include 50 Hz and 60 Hz. Confirm that the reactor’s rating aligns with the drive and local power system rather than selecting by drive horsepower alone.
A load reactor may be appropriate when a VFD supplies a motor through a long cable or when the drive manufacturer identifies an output-side concern. The fast switching of a VFD can produce voltage transitions that interact with motor-lead characteristics, so the cable, motor, drive, and switching conditions should be evaluated together. An output reactor can moderate these transitions, but it does not necessarily provide the same level of control as a purpose-designed dv/dt filter or sine-wave filter.
If you are looking for more details, kindly visit ANNEZEE.
There is no single motor-cable distance that makes a load reactor mandatory for every installation. A cable length of 100 ft (about 30 m) can be used as a prompt to review the drive and motor manufacturers’ guidance, not as a universal threshold. Actual requirements vary with drive design, cable construction, motor insulation, grounding, and operating conditions.
First determine whether the issue is on the supply side or the motor side. Input-side disturbances or drive-input considerations point toward evaluating a line reactor. Long motor leads or concerns about the drive output reaching the motor point toward evaluating a load reactor or another output-conditioning device.
Provide the supplier with the system voltage, phase, frequency, drive model, rated current, and motor details. Also share the required impedance, if already specified, and whether the reactor will operate continuously or under a particular duty cycle. A reactor selected only by nominal horsepower may not match the drive’s actual current or installation conditions.
Check enclosure space, mounting orientation, ambient temperature, ventilation, and the expected operating environment. Reactor losses generate heat, so installation and cooling requirements matter to reliable operation. Confirm clearances, terminal arrangements, and applicable project requirements before finalizing the design.
For a useful quotation, share the application diagram or a clear description of where the reactor will be installed. Include the VFD and motor ratings, supply conditions, cable length, operating environment, quantity, and any required dimensions or connection details. This information helps a supplier evaluate whether a line reactor, load reactor, or a different solution should be considered.
ANNEZEE supports B2B buyers evaluating electrical equipment requirements and reactor specifications. Our team can review the application information you provide and discuss suitable configuration, ratings, and sourcing needs. Because selection depends on the actual installation, final compatibility should be confirmed against the drive and motor documentation.
An electrical reactor adds inductive impedance to an AC circuit. Choose a line reactor when the requirement is on the VFD’s incoming supply side, and evaluate a load reactor when the concern is between the VFD output and motor. They serve different positions in the system and should not be treated as substitutes.
Your next step is to identify the problem location, gather the drive, motor, supply, and cable details, and compare them with manufacturer guidance. Send these requirements to ANNEZEE to discuss reactor selection and sourcing for your project.
Want more information on What Is an Electrical Reactor? Line Reactors vs Load Reactors? Feel free to contact us.