Eddy currents are electrical currents generated in conductive materials when they are exposed to a changing magnetic field. This physical phenomenon has various industrial applications and is particularly useful in recycling, where it enables non-ferrous metals, such as aluminium and copper, to be separated from other materials.
In a recycling plant, eddy current separators make it possible to recover metallic materials from mixed waste streams without having to manually sort each individual piece.
Their operation is based on electromagnetic induction: a magnetic rotor generates a changing magnetic field that produces a repulsive force on certain conductive metals, altering their trajectory and facilitating their separation.
What are eddy currents?
Eddy currents, also known as Foucault currents or induced currents, are electrical currents induced within a conductive material when it experiences a change in the magnetic field.
Unlike the electrical current flowing through a wire connected to a power supply, eddy currents are generated within the material itself through electromagnetic induction.
Their behaviour is explained by two physical principles:
- Faraday’s law: a change in magnetic flux can induce electrical currents in a conductive material.
- Lenz’s law: induced currents generate a magnetic field whose effect opposes the change that produces them.
When this phenomenon is applied appropriately, the interaction between magnetic fields can generate a force that moves the conductive material.
This principle is used in various industrial applications, including braking systems, material testing and metal separation equipment.
In the recycling industry, its main application is the recovery of conductive non-ferrous metals from mixed waste streams.
How does an eddy current separator work?
An eddy current separator is a machine that uses electromagnetic induction to separate conductive non-ferrous materials from other types of waste.
It generally consists of a conveyor belt and a high-speed magnetic rotor positioned near the discharge end. The rotor contains alternating-polarity magnets that generate a rapidly changing magnetic field.
When a conductive metal passes through this field, electrical currents are induced within it. The electromagnetic interaction generates a force that changes its trajectory compared with non-conductive materials.
The process can be divided into five stages.
1. Material preparation and feeding
Waste reaches the separator through a conveyor belt or feeding system.
To improve separation, the material should be distributed evenly, avoiding accumulations and overlapping that could prevent some particles from being exposed to the magnetic field.
Depending on the composition of the waste, preliminary shredding, screening or sorting operations may be necessary.
2. Preliminary separation of ferrous metals
Before using an eddy current separator, ferromagnetic materials, such as iron and certain types of steel, are normally removed.
Magnetic separators, including overband systems, magnetic pulleys and magnetic drums, are used for this purpose.
This operation improves the operating conditions of the eddy current separator and reduces interference from ferrous materials.
3. Generation of a changing magnetic field
The separator’s rotor spins at high speed, generating a changing magnetic field in the discharge area.
When conductive metal particles pass through this region, electrical currents are induced within them.
The strength of the response depends on factors such as the material’s electrical conductivity, mass, geometry and dimensions.
4. Repulsion and change of trajectory
The interaction between the induced currents and the rotor’s magnetic field produces a force on the metal particles.
As a result, conductive metals suitable for this process are propelled along a different trajectory from the one they would follow if they left the conveyor solely under the influence of gravity.
Non-conductive materials, such as certain plastics, glass or wood, do not experience the same repulsive force and follow a trajectory closer to their natural falling path.
5. Collection of separated fractions
A physical separation system, usually an adjustable splitter, is installed in the discharge area.
This component allows the propelled metallic materials and the rest of the mixture to be collected separately.
The result is a series of distinct fractions that can be sent to further sorting, conditioning or recovery stages.
It is important to note that the separator does not identify each type of metal individually or guarantee a fraction of absolute purity. Additional processes may be required to distinguish between alloys or separate certain metals from one another.

Which metals can be separated using eddy currents?
Eddy current separators are primarily used to recover non-ferrous metals with sufficient electrical conductivity.
The most common materials include aluminium, copper and certain alloys, such as brass.
Not all materials respond in the same way. Their behaviour depends on the relationship between their electrical properties, mass and geometry, as well as the equipment configuration.
| Material | Typical behaviour |
|---|---|
| Aluminium | Responds well to induction and is one of the main metals recovered |
| Copper | Can be recovered using eddy currents, although its higher density affects its trajectory |
| Brass | Recoverable under certain conditions of size, shape and equipment configuration |
| Zinc and certain alloys | Separation depends on the characteristics of the material and equipment |
| Iron and ferromagnetic steel | Preferably removed through preliminary magnetic separation |
| Stainless steel | Many types cannot be effectively separated using conventional eddy current equipment |
| Plastic, glass and wood | Do not generate the same electromagnetic response and follow a different trajectory |
Therefore, the purpose of this technology is not to separate any metal from any type of waste, but to recover specific conductive metal fractions under suitable processing conditions.
Difference between magnetic separation and eddy current separation
Although both technologies use magnetic fields, their operating principles and applications are different.
Conventional magnetic separation uses the attraction experienced by ferromagnetic materials when exposed to a magnet.
Eddy current separation, on the other hand, uses currents induced in conductive materials to generate a force that changes their trajectory.
| Feature | Magnetic separation | Eddy current separation |
|---|---|---|
| Principle | Magnetic attraction | Electromagnetic induction and repulsive force |
| Typical materials | Iron and ferromagnetic steel | Aluminium, copper and other conductive non-ferrous metals |
| Equipment | Overband separators, magnetic pulleys and drums | Eddy current separators |
| Main function | Removal of ferrous metals | Recovery of non-ferrous metals |
| Typical position | Preliminary stage | Stage following ferrous metal removal |
These technologies are complementary.
In a mixed waste recycling line, they are commonly combined to recover different metallic fractions and improve the quality of the material sent to subsequent processing stages.
Applications of eddy currents in recycling
Eddy current separation is used in various facilities where waste contains mixtures of metallic and non-metallic materials.
Municipal solid waste (MSW) treatment plants
Municipal waste may contain aluminium packaging and other metallic items mixed with plastics, paper, glass and organic matter.
After the necessary sorting and conditioning stages, eddy current separators can be used to recover non-ferrous metals present in the waste stream.
In municipal solid waste treatment plants, this technology can form part of a sequence of equipment designed to obtain different recoverable material fractions.
Industrial waste treatment plants
Industrial waste can have a heterogeneous composition and contain mixtures of metals, plastics, wood, paper and other materials.
Recovering non-ferrous metals reduces their presence in the remaining fractions and produces materials that can be sent to subsequent recycling processes.
In industrial waste recycling plants, Reverter Industries considers the integration of magnetic and eddy current separation systems alongside shredding, screening and sorting equipment.
Construction and demolition waste (CDW) recycling plants
Waste from construction and demolition activities may include concrete, aggregates, wood, plastics and various metallic components.
Following material preparation and sorting, eddy current separation can help recover certain non-ferrous fractions and reduce their presence in other recovered materials.
Its integration depends on the composition of the waste and the configuration of the construction and demolition waste recycling plant.
Scrap metal recycling facilities
When processing mixed scrap metal, metal separation is an important stage in obtaining fractions with suitable characteristics for recovery.
Magnetic systems remove ferrous materials, while eddy current separators can recover conductive non-ferrous metals.
This technology complements other operations involved in the scrap metal recycling process, such as sorting, shredding and screening.
What factors influence separation efficiency?
The performance of an eddy current separator does not depend solely on the power or operating speed of the rotor.
The characteristics of the waste and the operating conditions of the entire processing line must also be considered.
Particle size and granulometry
Particle size affects the electromagnetic response and the trajectory of the material.
Highly heterogeneous fractions can make recovery more difficult. For this reason, some facilities include preliminary screening stages to process materials within more uniform particle size ranges.
Conductivity, density and geometry
Two metal pieces of similar size may respond differently.
The electrical conductivity, density and shape of each fragment influence the force it experiences and its behaviour when leaving the conveyor.
Therefore, it should not be assumed that all non-ferrous metals can be separated with the same efficiency.
Material distribution
Uniform feeding improves the exposure of particles to the magnetic field.
When waste arrives in piles or overlapping layers, some pieces may be hidden beneath others, making separation more difficult.
Dosing and feeding systems help maintain a more consistent material flow.
Conveyor speed and rotor configuration
The conveyor speed, rotor characteristics and rotor position influence the discharge trajectory of the materials.
These parameters must be adapted to the size, composition and behaviour of the fraction to be recovered.
Separator splitter adjustment
The position of the splitter determines where the material trajectories are divided.
Incorrect adjustment can result in the loss of recoverable metals or the inclusion of unwanted waste in the recovered metal fraction.
Moisture and the presence of impurities
Moisture, adhering materials and accumulations of fine particles can affect material distribution and separation.
Depending on the input conditions, additional cleaning, drying or conditioning stages may be appropriate.
Actual recovery performance must be assessed by considering the composition of the waste and the results obtained under representative operating conditions. There is no single efficiency percentage applicable to every installation.
How are eddy current separators integrated into a recycling plant?
An eddy current separator usually forms part of a larger waste treatment line.
Depending on the input material and recovery objectives, a typical configuration may include the following operations:
- Reception and dosing: regulation of the waste flow entering the facility.
- Shredding or size reduction, when necessary: preparation of the material to facilitate subsequent operations.
- Screening: classification into more uniform particle size fractions.
- Magnetic separation: removal of iron and other ferromagnetic materials.
- Eddy current separation: recovery of conductive non-ferrous metals.
- Additional sorting: further operations to improve the quality of the recovered fractions.
This sequence is illustrative. The final order and the need for each stage depend on the waste being processed and the requirements of the project.
For example, a facility receiving previously sorted materials may require fewer conditioning stages than one processing mixed industrial waste.
Likewise, recycling machinery should be selected according to processing capacity, waste composition and the plant’s recovery objectives.
At Reverter Industries, the integration of shredding, conveying, screening and separation technologies makes it possible to configure treatment solutions adapted to different industrial applications.
Advantages and limitations of eddy current separators
The main advantage of this technology is its ability to recover certain non-ferrous metals through an automated process, without relying exclusively on manual sorting.
Its benefits include the recovery of valuable materials, the reduction of impurities in other fractions and the possibility of integration into continuous processing lines.
However, it also has limitations.
Materials that do not generate a sufficient electromagnetic response cannot be effectively recovered using this system. Likewise, particle size, material distribution and waste conditions can reduce performance.
The separator does not replace every other sorting technology. Obtaining aluminium, copper or other alloy fractions with a specified purity may require additional equipment and processing operations.
For this reason, equipment selection should consider the entire treatment process, rather than the individual characteristics of the separator alone.
Frequently asked questions about eddy currents
What are eddy currents used for in recycling?
They are used to recover certain conductive non-ferrous metals present in mixed waste streams. Eddy current separators generate a changing magnetic field that induces electrical currents in metal particles, producing a force that changes their trajectory and facilitates their separation.
What materials can an eddy current separator recover?
Mainly aluminium, copper and certain conductive alloys, depending on particle size and characteristics. It is not a system designed to recover plastics, glass or wood, nor does it replace magnetic separation for iron and ferromagnetic steel.
Can eddy currents separate aluminium and copper from each other?
A conventional separator can recover different conductive non-ferrous metals together from the rest of the waste stream. However, it does not guarantee the individual separation of aluminium and copper. Additional sorting technologies may be required to obtain distinct fractions.
Why is a magnetic separator used before an eddy current separator?
Because it removes iron and other ferromagnetic materials beforehand. This reduces interference and helps protect the eddy current equipment, while also facilitating subsequent non-ferrous metal recovery.
What is the difference between an eddy current separator and a magnetic separator?
A conventional magnetic separator attracts ferromagnetic materials. An eddy current separator induces electrical currents in conductive materials, generating a repulsive force. Both technologies are used in a complementary way.
Can eddy current separators be integrated into existing facilities?
Yes, provided that the characteristics of the material flow and the conditions of the facility allow their integration. The equipment upstream and downstream, available space, feeding system and separation objectives must be evaluated.
Metal separation in recycling plants: an integrated solution
Efficient recovery of metallic materials requires combining different technologies according to the composition of the waste and the desired results.
Eddy current separators are an important tool for recovering non-ferrous metals, but their performance depends on material preparation and integration with the other equipment in the processing line.
Reverter Industries designs and integrates waste treatment and sorting solutions, combining conveying, shredding, screening and separation technologies according to the requirements of each facility.
If you need to assess the integration of separation systems or improve an existing plant’s processes, contact our technical team to evaluate the specific requirements of your project.
























