Oct. 20, 2026
Electrical Equipment & Supplies
Electrical reactors are inductive components used to control current, limit fault levels, support power quality, or protect equipment from electrical stress. The main types include line reactors, DC link chokes, output reactors, harmonic-filter reactors, current-limiting reactors, and shunt reactors. Their applications range from low-voltage frequency converters and motor systems to power distribution networks. To select one, match its function, voltage, current, frequency, impedance, installation conditions, and coordination requirements to the specific system.
This guide is for engineers, panel builders, OEMs, procurement teams, and electrical equipment distributors evaluating reactors for a new design or replacement project. It is especially relevant when a system includes a frequency converter, sensitive electronic loads, a transformer, or equipment exposed to high fault currents. The right choice depends on where the reactor is installed and what problem it must address. A component described simply as an “electrical reactor” may therefore refer to products with very different electrical duties.
An electrical reactor is an inductor designed for a defined power-system duty. Its winding and magnetic core create inductive reactance, which opposes changes in current in an AC system. The reactor’s impedance, current rating, insulation, thermal design, and connection position determine how it affects the circuit. A reactor does not replace correct system protection or eliminate every harmonic or voltage issue; it is one element of a coordinated electrical design.
For frequency-related context, industrial power systems commonly operate at 50 Hz or 60 Hz, while a frequency converter varies its output frequency to control motor speed. A reactor connected to the converter’s input does not perform the same task as one connected between the converter and motor. Identifying the point of installation is therefore a useful first step in choosing a type.
A line reactor is installed on the AC supply side of a drive or other power-electronic equipment. It adds impedance between the supply and the device, which can help limit current transients and reduce the effect of some supply disturbances on the equipment. It may also contribute to reducing harmonic current, depending on the system and reactor design. Buyers should confirm the intended duty with the drive manufacturer or system designer rather than assume that any input reactor will address every power-quality concern.
A DC link choke is installed in the DC bus of a converter, where it helps smooth current in the intermediate DC circuit. Some converters include a built-in choke, while others may allow or require an external component. The correct choice depends on the converter topology, bus design, manufacturer instructions, and required performance. Before specifying one, confirm whether the converter already provides the relevant DC-link function.
An output reactor is placed between a frequency converter and a motor. It can help manage the electrical effects of the converter’s output waveform on the motor cable and connected equipment. Its suitability depends on factors such as cable length, switching conditions, motor insulation capability, and the drive manufacturer’s recommendations. Where the application has demanding cable or motor requirements, a sine-wave filter or another output solution may be more appropriate than a standard output reactor.
Reactors are also used with capacitors in power-factor correction and harmonic-control arrangements. A detuned reactor is selected as part of a capacitor bank to shift the circuit’s resonant behavior away from problematic harmonic conditions. The reactor and capacitor must be designed as a coordinated combination for the system’s voltage, frequency, harmonic environment, and operating profile. Substituting a reactor based only on physical fit or nominal current can change the intended tuning and create an unsuitable installation.
Current-limiting reactors are used in power systems to add impedance and help control prospective short-circuit current. Shunt reactors are connected across a power-system circuit and are used in some higher-voltage applications to absorb reactive power and manage voltage under particular operating conditions. These are system-level applications that require engineering analysis, protection coordination, and clearly defined operating parameters. They should not be selected using the same criteria as a low-voltage drive reactor.
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| Application or location | Reactor type to evaluate | Key design question |
|---|---|---|
| AC supply feeding a frequency converter | Line or input reactor | What supply conditions and drive requirements must it accommodate? |
| Converter DC bus | DC link choke | Is a choke already integrated, and what does the converter manufacturer specify? |
| Converter-to-motor connection | Output reactor or filter | What are the cable length, motor, and output-waveform requirements? |
| Capacitor bank in a harmonic environment | Detuned reactor | What capacitor and system conditions define the required tuning? |
| Network fault-current or voltage-management design | Current-limiting or shunt reactor | What system study, protection scheme, and operating duty apply? |
This table is a starting point, not a substitute for a circuit review. For example, a drive may need an input reactor, an output reactor, both, or neither, depending on its design and operating conditions. The specified function should be stated in the purchase documents so that suppliers can evaluate equivalent products on the same basis.
State what the reactor should do and where it will be connected. Identify whether the priority is input-side protection, DC-bus smoothing, output-side motor-circuit support, harmonic-system coordination, or fault-current limitation. If the project description only gives a product name, ask the design team to clarify the required behavior. This reduces the risk of comparing products that are not functionally equivalent.
Provide the system voltage, operating frequency, rated current, phase arrangement, and load or converter information. Reactor current must be suitable for the connected duty and operating profile; it should not be chosen from a motor nameplate alone without checking the complete circuit design. Specify any required impedance or reactance value where the engineering design has established one. A 3% impedance reactor, for example, is a design option used in some drive applications, not a universal recommendation for every converter or supply.
Record the enclosure type, available space, mounting orientation, ambient conditions, ventilation, and expected operating cycle. Confirm terminal style, conductor clearances, insulation requirements, and any acoustic or environmental constraints that matter to the installation. These details can affect product configuration and suitability. Ask the supplier to identify the assumptions used if the final enclosure or operating environment has not yet been fixed.
Check the reactor against the converter, motor, capacitor bank, protective devices, and upstream supply as applicable. For filter or capacitor-bank applications, the reactor must be coordinated with the associated components rather than selected independently. For output-side use, follow the drive manufacturer’s limits and recommendations concerning cable and motor conditions. A supplier can review stated specifications, but system-level performance should be confirmed by the responsible electrical designer.
Reactor pricing depends on electrical ratings, construction, materials, quantity, customization, and required documentation. Minimum order quantities and production lead times vary by supplier, product configuration, and current production schedule, so they should be confirmed for each inquiry rather than assumed. A technically complete request can make quotations easier to compare and reduce clarification cycles. Include the required quantity, delivery destination, target schedule, and any inspection or packaging requirements.
At ANNEZEE, we support B2B buyers evaluating electrical reactors by reviewing the application details and matching them with an appropriate product configuration. To help us assess a requirement, share the connection point, system voltage and frequency, rated current, required impedance if defined, operating environment, quantity, and target delivery schedule. We can then clarify the information needed for product evaluation and quotation without treating an incomplete specification as a confirmed design.
The best electrical reactor is the one selected for a defined duty, not simply the one with a familiar name or matching nominal rating. Line reactors, DC link chokes, output reactors, detuned reactors, current-limiting reactors, and shunt reactors serve different parts of electrical systems. Begin by identifying the installation point, then verify ratings, system coordination, environmental conditions, and supplier documentation. This approach helps buyers compare suitable products and avoid specifying components that do not address the project requirement.
For your next step, prepare a circuit or equipment description and a complete rating sheet, then request a quotation based on those details. If you are sourcing an electrical reactor for a low-voltage frequency converter or another electrical equipment application, contact ANNEZEE with your project requirements for a focused product review and B2B supply discussion.
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