Air core reactor is a type of harmonic filter. At medium and high voltage levels, harmonic filters are generally designed, specified and manufactured using iron core reactors or air core reactors. Under normal circumstances, the voltage of the transmission and distribution system needs to be kept within a strict range. However, due to the capacitive characteristics of the power grid, the voltage will increase during operation. Therefore, the Air core reactor comes in handy.
This post provides useful information about the air core reactor and various maintenance suggestions. I hope you can have a perfect experience in the later use process. Dig in the post now!
1.What Is The Reactor?
2.What Are The Main Parameters For Reactors?
3.What Is The Air Core Reactor?
4.What Are The Applications For Air Core Reactor?
5.What Are The Key Benefits Of Air Core Reactor?
6.What Are The Disadvantages Of Air Core Reactor?
7.What Are The Designs Of Air Core Reactor?
8.What Are The Types Of Air Core Reactor?
9.What Are The Working Conditions Of Air Core Reactor?
10.What Are The Accessories For Air Core Reactor?
11.What Are The Operations Before Use Of Air Core Reactor?
12.What Are The Maintenance Tips For Air Core Reactor?
What Is The Reactor-sourced: LTEC
A reactor is a passive two-terminal electrical component. It is also called a line reactor or choke. When current flows through it, it stores electrical energy in a magnetic field, thereby blocking changes in current, protecting against voltage spikes and transients, stabilizing voltage, and protecting electrical equipment.
The main parameters that determine the performance and application of reactors include:
Inductance (L)
Inductance (L)-sourced: electricaltechnology
Inductance represents the ability of the reactor to resist changes in current, usually in Henry (H). Its value generally varies from microhenry (µH) to millihenry (mH). Industrial reactors are even in Henry. The inductance value of the reactor generally depends on the number of turns, core material and geometry.
Rated current (I)
Rated current (I)-sourced: kebamerica
The rated current refers to the maximum continuous current that the reactor can withstand without overheating. It mainly includes peak/surge current, that is, the maximum short-term current before saturation or damage.
DC resistance (DCR)
DC resistance (DCR)-sourced: researchgate
DC resistance refers to the inherent resistance of the reactor winding, usually in ohms (Ω). It is prone to power loss (I²R loss) and heating of the device.
Saturation current
Saturation current-sourced: sstatic
Saturation current refers to the current level when the core material reaches saturation. It causes a sharp drop in inductance. And the key role is to avoid the loss of inductive characteristics in high current applications.
Quality factor (Q)
Quality factor (Q)-sourced: allelcoelec
Quality factor is the ratio of inductive reactance to resistance (R) at a given frequency. The higher the quality factor value, the lower the energy loss.
Self-resonant frequency (SRF)
Self-resonant frequency (SRF)-sourced: everythingrf
The self-resonant frequency refers to the frequency at which the inductance of the reactor resonates with its parasitic capacitance. When the current exceeds the self-resonant frequency, the reactor behaves like a capacitor.
Core material
Core material-sourced: researchgate
The core material of the reactor can be divided into air core, ferrite core, iron powder core and laminated silicon steel. Air core refers to no core (low inductance, no saturation, used for high-frequency applications). Ferrite core refers to high permeability, suitable for high-frequency inductors. Iron powder core is generally used for power inductors with medium saturation. Laminated silicon steel is generally used for low-frequency power reactors (for example, line reactors).
Temperature rise and thermal characteristics
The temperature rise and thermal characteristics refer to the maximum operating temperature. It is mainly limited by the insulation and core materials. Thermal resistance (°C/W) refers to the speed of heat dissipation.
Insulation and voltage rating
Insulation and voltage rating-sourced: sstatic
The voltage rating is the maximum voltage that the reactor can withstand. The insulation class determines the thermal resistance of the device (e.g., class B, F, H).
Frequency range
The frequency range refers to the operating frequency of the device. Reactors perform differently at low and high frequencies.
Air core reactors, also known as air core inductors, are an inductive component. They have no magnetic core and rely solely on the self-inductance of the coil windings in free air (and sometimes a non-magnetic support structure).
The main features of air core reactors are:
No magnetic core
No magnetic core-sourced: wikimedia
Unlike iron core reactors, air core reactors do not use magnetic materials in their construction. They generally use air or non-magnetic materials such as plastic, ceramic, or fiberglass for structural support.
Linear inductance
The coreless design allows the inductance to remain stable even at high currents. This design is ideal for high current or high frequency applications.
Low losses at high frequencies
The lack of core losses is ideal for RF and high frequency circuits.
Low inductance values
Low inductance values-sourced: allaboutcircuits
Air core reactors generally offer lower inductance values than iron core reactors. However, it requires more turns or larger coils to achieve comparable inductance values to iron core reactors.
No hysteresis or eddy current losses
No hysteresis or eddy current losses-sourced: motioncontroltips
Because there is no ferromagnetic material, air core reactors have very low losses, which improves efficiency in high frequency applications.
High self-Resonant frequency (SRF)
Due to the low parasitic capacitance, air-core reactors can operate in a very high frequency range.
From the functional point of view, the application scope of aire core reactor is:
Current limiting
Current limiting-sourced: nextpcb
Air core reactor can be connected in series to transmission lines or feeders for current limiting and circuit protection. In the event of a short circuit or fault in the system, it can protect the entire system.
Neutral point grounding
Neutral point grounding-sourced: zandz
Air core reactor can be used for neutral point grounding of three-phase power grids. It can limit the current when a fault occurs between the phase line and the ground line.
Harmonic filtering
Harmonic filtering-sourced: sciencedirect
When large induction motors are running, the power grid is prone to distortion and harmonics. Air core reactors can filter or eliminate harmonics, control system faults, reduce losses, and improve system power efficiency.
From the application industry and system, air core reactors can be used for:
RF circuits and antenna systems
RF circuits and antenna systems-sourced: toyon
Air core reactors are used for tuning circuits, filters, and impedance matching (due to high self-resonance frequency).
High-frequency power electronics
High-frequency power electronics-sourced: nwl
Air core reactors can be used in high-frequency power electronics for switching power supplies (SMPS), resonant converters, and Tesla coils.
Power systems
Power systems-sourced: researchgate
Air core reactors can be used in power systems to limit fault currents and filter harmonics.
Medical and scientific equipment
Medical and scientific equipment-sourced: sanmedicalsupply
It can also be used in MRI machines, induction heaters and high voltage experiments.
Audio and signal processing
Air core reactor can also be used in high-end audio crossover systems, suitable for audio and signal processing.
What Are The Key Benefits Of Air Core Reactor-sourced: adp
Air core reactor is a very cost-effective solution for reactive power compensation in power transmission and distribution systems. Its main advantages include:
High strength
Air core reactor can withstand high short-circuit currents and high mechanical strength. And low noise, suitable for noise-sensitive applications.
Low maintenance requirements
Air core reactor has low maintenance requirements. The equipment is compact and suitable for installation in compact areas. After surface pre-treatment, it can resist UV and pollution. Low maintenance requirements and more environmentally friendly.
Economic and efficient
Air core reactor is installed in system voltages up to 500kV and can be directly connected to the substation bus, the end of the transmission line or
the tertiary winding of a large power transformer. This method is more economical and efficient.
High quality and reliability
Air core reactor generally uses first-class materials and production processes to ensure the high quality and reliability of the equipment. The temperature rise and dielectric design are more conservative, thereby extending the service life of the equipment.
The main disadvantages of air core reactors include:
Low inductance per unit size
Low inductance per unit size-sourced: examples
Compared with iron core reactors, air core reactors have lower inductance per unit size. If the inductance is the same as that of iron core, a larger coil is required.
High electromagnetic interference (EMI)
High electromagnetic interference (EMI)-sourced: emheater
If the air core reactor adopts an unshielded design, it may radiate more noise.
High mechanical fragility
Due to the hollow structure, air core reactors usually require structural support (e.g. epoxy resin, ceramic skeleton).
What Are The Designs Of Air Core Reactor-sourced: hilkar
Air-core reactors generally use a glass fiber encapsulation structure. Its windings are composed of multiple insulated aluminum conductors, which are mechanically fixed in epoxy resin-impregnated glass fibers to form a cylinder or multiple cylinder brackets.
Each cylinder is separated by vertical glass fiber spacers to form a cooling channel. This structural design can reduce the installation footprint.
There are many types of air-core reactors, mainly including the following:
Shunt reactors
Shunt reactors-sourced: studyelectrical
Shunt air-core reactors are devices specially used to compensate for common transmission lines or cables. Under low load conditions, they allow more active current energy to flow through the system and reduce the voltage rise caused by the transmission line capacitance, thereby reducing corona losses.
Static VAR compensation reactors
Static VAR compensation reactors-sourced: eprlab
Static VAR compensation reactors are generally suitable for large motors or other industrial devices with variable loads. It is mainly used to provide dynamic voltage stability of the power system. Its typical application industries include steel mills, cranes, induction cookers, paper mills, mining companies, etc.
Damping reactors
Damping reactors-sourced: teee-group
Damping reactors are mainly composed of one or more capacitors in series. It can limit the surge current generated during system operation and provide a specified impedance so that the system can withstand the rated current as well as the high-frequency discharge current of the capacitor bank and the fault current when the circuit is short-circuited.
Discharge reactors
Discharge reactors are a type of reactor in a series compensation system. It is generally connected in series with the capacitor bank in the transmission line. Its main function is to improve voltage regulation, improve system stability, increase transmission line capacity, reduce power loss and save costs.
Arc furnace series reactor
Arc furnace series reactor-sourced: arya-transfo
Arc furnace series reactor can provide the necessary power factor correction for the system and limit the extremely unstable arc furnace current and voltage.
Double current limiting reactor
Double current limiting reactor-sourced: studyelectrical
The double current limiting reactor can generate high reactance in the case of system failure and low reactance in the case of normal system, which can always maintain the isolation of the system.
Split-phase shunt reactor
The split-phase shunt reactor mainly adopts split-phase design, which can provide the system with sufficient sensitivity to detect turn-to-turn faults.
What Are The Working Conditions Of Air Core Reactor-sourced: squarespace
The environmental conditions in which the air-core reactor can be used are as follows:
- Place of use The air-core reactor can be used both outdoors and indoors.
- Ambient temperature The operating temperature range of the air-core reactor is from -40℃ to 45℃, and it can operate normally and stably.
- Altitude The air-core reactor needs to be used normally at an altitude below 1km.
- Maximum wind speed The maximum wind speed in the air-core reactor environment does not exceed 35m/second.
- Relative humidity The relative humidity environment used by the inductor is less than or equal to 90%.
- Seismic performance Under normal circumstances, the seismic performance of the reactor is 0.3g horizontally and 0.15g vertically.
- Precautions When using indoors, be sure to pay attention to the ventilation and heat dissipation of the air-core reactor. And the installation location must be clean, without any harmful gases, steam, conductive gases and explosive dust, etc.
Optional accessories for air-core reactors include:
Grading rings
Grading rings-sourced: coronaringfactory
If you need to eliminate visible corona, your air-core reactor can be equipped with some grading rings made of aluminum tubes.
Bird-proof fences
When air-core reactors are used outdoors, you can choose some birdproof fences. It is mainly composed of glass fiber reinforced plastic mesh that is resistant to high temperatures and UV rays. There are square openings on the mesh to prevent birds from adversely affecting the air-core reactor.
Insulators
Insulators-sourced: kvcable
You can choose some high-quality insulators to provide the necessary support for the air-core reactor.
Base
The base equipped with the air-core reactor can maintain the magnetic gap and electrical gap required by the reactor, thereby minimizing the inductive loss.
Casing
According to the customer's usage requirements, we can provide you with the shell of the reactor.
Before using the air-core reactor, you need to follow the following operations:
Check before power-on
To ensure that the supply reactor can operate safely, normally and stably. You need to conduct a thorough inspection before the equipment is powered on, including:
- Checking whether all electrical appliances are properly connected
- Checking all grounding connections, and whether the shell is connected
- Checking whether there are foreign objects in the coil that may hinder ventilation
- Checking whether the air-core reactor is firmly fixed and whether there is any looseness
- Checking whether the gap between the live parts and the cable grounding parts meets the specified standards
- Checking whether the shell of the reactor has any damage.
Commissioning test
Commissioning test-sourced: ecmag
Before officially using the reactor, you need to conduct a thorough commissioning test. This requires you to have a stable power supply on site, and the test includes DC resistance measurement, power frequency inductance or impedance measurement. Compare these actual data with the conventional test report values to control the accuracy of the equipment.
What Are The Maintenance Tips For Air Core Reactor-sourced: squarespace
Air-core reactors do not require maintenance under normal operating conditions, but regular maintenance and inspection can better stabilize the reactor's condition. In extreme environments, you can take the following measures to ensure the safe and stable operation of the reactor, including:
- Check whether the insulation layer, varnish or paint of the equipment is rusted, corroded or aged;
- Regularly clean and dry the site, and clean the dust or attachments on the equipment once a year;
- Pay attention to dirt accumulation on the insulator and supporting structure, and obstacles blocking the cooling pipes;
- Electrical connections are loose or corroded. Whether the insulation surface shows signs of overheating or voltage leakage.
As the power distribution system in modern society gradually develops and matures, the requirements for safety, stability and efficiency are getting higher and higher. Air-core reactors can well control the transmission voltage, improve system efficiency and reduce losses. LTEC is also a professional air-core reactor designer, manufacturer and exporter. If you have more questions or help about this type of equipment, you are welcome to consult us.
