Reactors, also known as inductors, are widely used in various power quality applications. Air-core and iron-core reactors are two key types. Their distinct characteristics meet varying power quality requirements. This post compares these two types of reactors, focusing on their key differences and advantages in application, while also providing additional information. We hope this post may address any questions you may have.
1. What Are The Air-Core Reactors?
2. What Are The Iron-Core Reactors?
3. What Are The Components Of Air-Core Reactors?
4. What Are The Components of Iron-Core Reactors?
5. What Are The General Comparsions of Air-Core Reactors And Iron-Core Reactors?
6. What Are The Types of Iron Core Reactors?
7. What Are The Comparison of Air-core And Iron-core Reactors?
What Are The Air-Core Reactors-sourced: ltreactor
Unlike iron-core reactors, air-core reactors lack a central magnetic core. This linear characteristic avoids saturation, but the gap between them and metal objects is larger, resulting in a larger device footprint.
Air-core reactors typically utilize windings made of wire, stranded wire, or copper or aluminum foil. Air-core reactors are generally supported by a mechanical structure and placed on an isolation insulator. The insulator determines the strength of the isolation system's potential relative to ground.
For the same inductance, air-core reactors typically have a greater number of turns than iron-core reactors. Furthermore, the lack of an iron core makes air-core reactors simpler and more lightweight.
What Are The Iron-Core Reactors-sourced: zhiyue
Iron-core reactors are primarily constructed from high-permeability laminated steel and an iron core material. The iron core directs the magnetic field through a well-defined path within the reactor's mechanical boundaries, eliminating stray magnetic fields.
Laminated steel is a soft magnetic material with nonlinear properties, so it saturates at high currents. Therefore, the iron core design incorporates linearization, adding an air gap to eliminate stray fields and stabilize the inductance.
What Are The Components Of Air-Core Reactors-sourced: researchgate
Air-core reactors primarily consist of aluminum or copper windings supported by an aluminum structure. The aluminum structure utilizes post-type insulators, minimizing insulation costs.
Due to the lack of an iron core, air-core reactors are typically larger, have a high number of turns, and are taller and larger in diameter. They also generate powerful stray magnetic fields. Therefore, they are often used in conjunction with rack-mounted capacitor banks, primarily in substations.
What Are The Components of Iron-Core Reactors-sourced: sciencedirect
Iron-core reactors primarily consist of copper or aluminum windings wound around an air-gapped iron core. They are typically housed within an enclosure, making them convenient for indoor or outdoor use. Iron-core reactors have a wide range of applications, including suppressing AC magnetic flux ripple in rectifier circuits, compensating for long-distance telephone lines, and limiting motor starting current.
They differ in:
| Air-core Reactors | Iron-core Reactor |
| Easier system isolation | Sophisticated isolation system |
| Mostly RMS current rating | Harmonic current rating |
| Cannot saturate | Limit of linearity |
| Large magnetic stray field | Stray field within the electrical spacing required by the system voltage |
| Open-air mounting on a concrete basement | Cubicle mounting with little space requirements |
Isolation System
Isolation System-sourced: wikipedia
The isolation system primarily refers to the physical distance between the core and the windings. Because iron-core reactors have fewer turns than air-core reactors, the potential difference between the turns is greater. The isolation system for air-core reactors only considers the windings, with the possible difference typically carried by the post insulators. Since the winding length of iron-core reactors is significantly shorter, the isolation system design for air-core reactors is even more critical.
Rated Current
The isolation system primarily determines the reactor's allowable temperature rise, while the rated current effectively measures the temperature rise and excess losses within the windings. In both air-core and iron-core designs, air-core reactor losses occur only in the windings. Iron-core reactor losses, on the other hand, consist of both winding and core losses.
Saturation
Air-core reactors generally utilize magnetically linear air to carry the magnetic field, meaning their inductance is independent of the current load. Air-core reactors also do not saturate. Iron-core reactors, on the other hand, primarily utilize magnetically nonlinear materials and saturate when the current exceeds the so-called linear current.
Stray Magnetic Fields
Stray Magnetic Fields-sourced: mdpi
Although iron-core reactors can saturate, they also minimize stray magnetic fields. Because exposure to magnetic fields can affect the human body, iron-core reactors require smaller mounting frames and space than air-core reactors, and nearby equipment is less susceptible to stray fields.
There are many types of iron-core reactors, including:
Filter Reactors
Filter Reactors-sourced: ltreactor
Filter reactors are primarily used to reduce harmonic levels in power systems. They can be coupled with capacitors and resistors.
Detuned Reactors
Detuned Reactors-sourced: ltreactor
Detuned reactors limit the harmonic currents of nonlinear loads on the reactor to within the fixed impedance range of components such as capacitors, transformers, and cables. They also suppress voltage increases in nonlinear load circuits.
Power Factor Correction Reactors
Power Factor Correction Reactors-sourced: ergunelektrik
Power factor correction reactors are specifically designed for power factor correction. They limit the current generated by harmonics on capacitors, preventing overheating and high current stress, and extending the life of the reactor.
Line Reactors
Line Reactors-sourced: transcoil
Line reactors are specifically designed for use on the input side of a frequency converter to mitigate harmonics, nuisance tripping, and voltage line notches.
Load Reactors
Load Reactors-sourced: rexpowermagnetics
Load reactors are specifically designed for use on the output side of a frequency converter to mitigate the effects of long lead lengths (reflected wave phenomenon) and reduce premature motor insulation failure.
The following mainly describes the differences between iron-core and air-core reactors.
Footprint
Footprint-sourced: hillar
Iron-core reactors have fewer turns and take up less space, allowing them to be placed close to other metal objects, such as inside an inverter enclosure. Air-core reactors have more turns, take up more space, and produce very strong stray magnetic fields. Therefore, when designing and using them, magnetic clearance should be considered against objects that may be subject to magnetic flux. Therefore, installation should consider areas such as steel fences and reinforced concrete.
Weight
Because they lack an iron core, air-core reactors have naturally high inductance and are lighter. Iron-core inductors, on the other hand, are heavier but take up less space overall.
Installation
Installation-sourced: mb-drive-services
Iron-core reactors are typically installed in a metal enclosure. This enclosure can be the inverter enclosure or a separate component. Due to the magnetic clearance, air-core reactors can be installed indoors or outdoors.
Core Saturation
Core Saturation-sourced: monolithicpower
Air-core reactors generally do not saturate. Iron-core reactors, however, do saturate. Specially designed iron-core reactors can achieve relatively higher saturation inductance. Designing an iron core with an air gap can reduce saturation effects.
Leakage Flux
Leakage Flux-sourced: quoracdn
Iron-core reactors have very low leakage flux, resulting in less interaction with surrounding equipment and less interference, making them easier to use with other devices. Air-core reactors have significant stray magnetic fields, which can easily affect the human body during use, requiring stronger isolation protection.
Cost
Air-core reactors are generally cheaper in terms of design, but they incur additional costs during use, such as occupying more space and using special non-magnetic steel, which can increase hidden costs. Iron-core reactors, on the other hand, incur additional material costs, but these offset the cost in terms of use.
This post briefly compares air-core and iron-core reactors, highlighting their key features. These details are crucial for different application scenarios. If you are a professional power engineer, you can consider which type to use based on the specific requirements of each project. If you have any further questions, please feel free to contact us.
