This article describes applications of eddy current. According to Faraday’s law of induction, The loop current is induced within the conductor when changing magnetic field links to the conductor. The loop current is called the eddy current. the eddy current flows in a plane perpendicular to the magnetic field in a closed loop within the conductor.
The following are the applications of eddy current.
- Crack Detection
- Condenser Tube Inspection
- Tube Testing
- Wire Testing
- Material Testing
- Weld Testing
- Coating Thickness Measurement
1. Application of Eddy Current in Crack Detection
Eddy current is used to detect the surface breaking cracks in the ferrous and non-ferrous. The high-frequency eddy current is used to find cracks in ferrous materials. And low-frequency eddy current is used to detect the cracks in the no-ferrous materials.
The subsurface cracks in ferrous materials can also be detected with the use of eddy currents, but the materials need to be magnetically saturated to remove the permeability effect. Eddy currents are most useful for the detection of surface cracks.
The small probe is used in high frequencies that cover a large area; it takes a long time. The frequencies of the order 2 MHz give high resolution.
Low-frequency crack detectors have a larger probe that allows suitable coil inductances. The low frequency is used as per the requirement of depth of eddy current penetration. The range of low frequencies is between 100Hz to l00kHz.
2. Condenser Tube Inspection
Eddy current testing is a commonly used non-destructive testing (NDT) method for inspecting condenser tubes, particularly in applications where detecting surface and near-surface defects is crucial.
The Eddy current inspection equipment has a probe or coil, a signal generator, and a receiver. The probe is placed near or in contact with the outer surface of the condenser tube. The signal generator sends AC through the probe coil, creating eddy currents within the tube wall.
The eddy current probe is now moved along the entire length of the tube at a controlled speed. The probe detects the change in the eddy current behavior caused by variations in the tube’s conductivity, thickness, and the presence of defects.
The Eddy current testing can provide information about both surface and subsurface defects, making it a valuable tool for detecting hidden flaws.
3. Tube Testing
The following procedure is used for testing the tubes.
- The tube to be inspected is passed through the probe.
- As the tube moves through the probe coil, it detects changes in eddy current behavior caused by variations in the tube’s wall thickness, conductivity, and the presence of defects.
4. Wire Testing
The following procedure is used for testing the wires.
- In the case of wire testing, the wire is typically stationary, and the rotating probe or coil is moved along the length of the wire.
- As the probe passes over the wire’s surface, it detects changes in eddy current behavior due to defects or variations in material properties.
5. Application of Eddy Current in Material Sorting
Eddy current separators are commonly used in recycling facilities to sort and separate various types of metal materials from mixed waste streams. These separators can efficiently extract aluminum, copper, and other non-ferrous metals from solid waste or crushed electronic waste.
Eddy current sorting is used to separate non-ferrous metals, such as aluminum, copper, and brass, from ferrous materials in industrial processes. For example, it can be employed in the aluminum recycling industry to segregate aluminum scrap from mixed metal waste.
Eddy current sorting can differentiate between different alloy compositions of the same metal type. This is valuable in industries requiring specific alloy properties, such as aerospace, automotive, and metallurgy.
Eddy current sorting is utilized in coin-sorting machines to separate coins of different compositions based on their electrical conductivity. This is commonly used in coin-counting and sorting machines found in banks and commercial establishments.
Eddy current sorting is utilized in coin-sorting machines to separate coins of different compositions based on their electrical conductivity. This is commonly used in coin-counting and sorting machines found in banks and commercial establishments.
Eddy current sorting can be applied in the electronics industry to sort and segregate components like capacitors, inductors, and connectors based on their electrical properties.
Eddy current testing is used to sort and categorize aerospace and automotive components made from conductive materials, ensuring that only components with the desired material properties are used in assembly.
Eddy current testing can sort materials based on their thickness or the presence of coatings, such as paint or plating. This is useful in industries where materials with specific thickness or surface finish requirements are needed.
6. Application of Eddy current in Weld Testing
It is possible to detect the following types of welding defects with the use of eddy current. The following are the applications of eddy current in weld testing.
- Cracks: The Eddy current testing is highly sensitive to detecting surface and near-surface cracks in welds.
- Porosity: It can identify voids, gas pockets, or other porosity types within the weld.
- Lack of Fusion: Incomplete fusion between weld layers or between the weld and base material can be detected.
- Weld Voids: Eddy current can identify voids or gaps in the weld structure.
7. Coating Thickness Measurement
The high near-surface resolution of eddy current testing makes it useful for accurately measuring metallic and paint coatings on metal substrates.
This is all about the applications of eddy current.