Various industrial and domestic applications of eddy current

1. Applications
Dr. Sukanta Debnath, Assistant Professor, SITCOE, YADRAV
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Eddy Current
Eddy
Current

2. Definition of eddy currents
• Brief explanation of how they are generated (moving
conductor in a magnetic field)
Principles of Eddy Currents
• Faraday's law of electromagnetic induction
• Lenz's law (eddy currents produce a magnetic field opposing
the change in magnetic flux)
EDDY CURRENT

3.  Non-Destructive Testing (NDT)
 Eddy Current Braking
 Eddy Current Separators
 Induction Heating
 Magnetic Levitation (Maglev)
 Other Applications
e.g., speed sensors in automotive industry, proximity sensors in machinery
APPLICATIONS OF EDDY CURRENT

4. NDT encompasses various methods and techniques, each
suitable for different types of materials, sizes, shapes, and
applications. Some common NDT methods include:
Ultrasonic Testing (UT)
Radiographic Testing (RT)
Magnetic Particle Testing (MPT)
Liquid Penetrant Testing (LPT)
Eddy Current Testing (ECT)
Visual Testing (VT)
Thermographic Testing (TT)
NON-DESTRUCTIVE TESTING (NDT)

5.  Principle:
ECT works on the principle of electromagnetic induction. When alternating current is passed
through a coil or probe, it generates a magnetic field. When this magnetic field interacts with
a conductive material, eddy currents are induced in the material. Any discontinuities or
defects in the material will disrupt the flow of eddy currents, causing changes in the
impedance of the coil or probe. These changes can be measured and analyzed to detect and
characterize defects.
 Equipment:
ECT equipment typically consists of a probe or coil connected to an instrument that
generates alternating current and measures the electrical properties of the material being
inspected. Probes may be of various designs, including pancake, bobbin, or rotating probes,
depending on the application and geometry of the material being tested.
 Applications:
 Surface Cracks and Defects: ECT is commonly used to detect surface cracks, pits,
corrosion, and other defects in conductive materials such as metals and alloys. It is
particularly effective for inspecting materials with complex shapes and surfaces.
 Heat Treatment Verification: ECT can be used to verify the effectiveness of heat
treatment processes by detecting changes in material properties and microstructure.
EDDY CURRENT TESTING (ECT)

6.  Sorting and Quality Control: ECT is used in manufacturing industries to sort and quality control
materials, ensuring that only defect-free components are used in production.
 Aerospace and Automotive: ECT is widely used in aerospace and automotive industries for
inspecting critical components such as engine parts, turbine blades, and aircraft fuselages.
 Advantages:
 Non-Destructive: ECT does not require the removal of material or surface coatings, preserving the
integrity of the inspected component.
 Fast and Efficient: ECT can rapidly scan large areas and provide immediate results, making it
suitable for high-volume production environments.
 Sensitive to Surface and Near-Surface Defects: ECT can detect defects located just below the
surface of the material, providing detailed information about the integrity of the component.
 Limitations:
 Limited Penetration Depth: ECT is most effective for inspecting surface and near-surface defects
and may have limited penetration depth in thicker materials.
 Material and Geometry Dependency: The effectiveness of ECT may vary depending on the
material properties and geometry of the component being inspected.
 Skill and Training: Interpreting ECT results requires specialized training and expertise to
distinguish between genuine defects and other anomalies.
EDDY CURRENT TESTING (ECT)

7. Eddy Current Braking is a braking mechanism that utilizes the principles of electromagnetic
induction to slow down or stop the motion of a conductive object. Here's an overview of Eddy
Current Braking:
 Principle:
Eddy Current Braking operates on the principle of electromagnetic induction. When a conductor,
such as a metal disc or rail, moves through a magnetic field, eddy currents are induced in the
conductor due to the changing magnetic flux. These eddy currents generate their own magnetic field,
which opposes the original magnetic field, resulting in a braking force that opposes the motion of the
conductor.
 Configuration:
In a typical setup, a stationary magnet or electromagnet creates a magnetic field, while the conductive
object (e.g., a metal disc or rail) moves through this magnetic field. As the conductive object moves,
eddy currents are induced in it, creating a braking force that slows down the motion.
 Applications:
 Trains and Railways: Eddy Current Braking is used in train systems for regenerative braking,
where the kinetic energy of the moving train is converted into electrical energy and returned to the
power grid.
 Roller Coasters: Eddy Current Braking is employed in roller coaster systems to control the speed
and bring the ride to a safe stop at the end of the track.
EDDY CURRENT BREAKING

8.  Exercise Equipment: Some stationary exercise bikes and elliptical trainers utilize eddy current
braking systems to provide smooth and adjustable resistance for users.
 Advantages:
 Smooth and Quiet Operation: Eddy Current Braking systems provide smooth and quiet braking
without the need for physical contact between braking elements, reducing wear and noise.
 Adjustable Braking Force: The braking force in eddy current braking systems can be adjusted by
varying the strength of the magnetic field or controlling the speed of the moving conductor,
allowing for precise control over braking.
 Limitations:
 Heat Generation: Eddy Current Braking can generate significant heat in the conductor due to the
resistance of the eddy currents, requiring cooling systems to prevent overheating.
 Limited to Conductive Materials: Eddy Current Braking is only effective on conductive materials
such as metals, limiting its applicability in certain situations.
EDDY CURRENT BREAKING

9. Eddy Current Separators are devices used to separate non-ferrous metals from non-metallic materials
based on their conductivity and magnetic properties. Here's an overview of Eddy Current Separators:
 Principle:
Eddy Current Separators operate on the principle of electromagnetic induction. When a conductor,
such as a non-ferrous metal, passes through a changing magnetic field, eddy currents are induced in
the conductor. These eddy currents create their own magnetic field, which interacts with the original
magnetic field, resulting in a repulsive force that propels the conductor away from the source of the
magnetic field.
 Configuration:
In a typical setup, a conveyor belt carries a mixture of materials, including both non-ferrous metals
and non-metallic materials, towards the Eddy Current Separator. A rotating magnetic drum or rotor
generates a changing magnetic field, inducing eddy currents in the non-ferrous metals. The repulsive
force caused by the interaction between the eddy currents and the magnetic field propels the non-
ferrous metals away from the conveyor belt, separating them from the non-metallic materials.
 Applications:
 Recycling Industries: Eddy Current Separators are commonly used in recycling facilities to
separate non-ferrous metals, such as aluminum, copper, and brass, from non-metallic materials,
such as plastic, glass, and rubber. These separated metals can then be recovered and recycled,
reducing waste and conserving resources.
EDDY CURRENT SEPARATORS

10.  Waste Management: Eddy Current Separators are employed in waste management facilities to
recover valuable non-ferrous metals from mixed waste streams, diverting them from landfills and
incinerators.
 Scrap Metal Processing: Eddy Current Separators are utilized in scrap metal processing plants to
sort and separate non-ferrous metals from ferrous metals and other materials, allowing for efficient
recycling and resource recovery.
 Advantages:
 Efficient Separation: Eddy Current Separators provide efficient separation of non-ferrous metals
from non-metallic materials, allowing for the recovery and recycling of valuable metals.
 Continuous Operation: Eddy Current Separators can operate continuously, processing large
volumes of material at high speeds, making them suitable for industrial-scale applications.
 Versatility: Eddy Current Separators can be adjusted to optimize the separation of different types of
non-ferrous metals and materials, maximizing recovery rates and product quality.
 Limitations:
 Limited to Conductive Materials: Eddy Current Separators are only effective for separating
conductive materials, such as metals, from non-conductive materials. They are not suitable for
separating ferrous metals, which require different separation techniques.
 Initial Investment: Eddy Current Separators require an initial investment in equipment and
infrastructure, which may be a barrier for smaller recycling operations or facilities.
EDDY CURRENT SEPARATORS

11. Induction heating is a process that utilizes eddy currents induced by electromagnetic induction to heat
electrically conductive materials. Here's an overview of induction heating using eddy currents:
 Principle:
Induction heating relies on the principle of electromagnetic induction. When alternating current (AC)
flows through a coil or induction heating coil, it generates a rapidly alternating magnetic field. When
a conductive material, such as metal, is placed within this magnetic field, eddy currents are induced
in the material. The resistance of the material to the flow of these eddy currents causes it to heat up
due to Joule heating, which is the conversion of electrical energy into heat.
 Equipment:
The basic components of an induction heating system include a power supply, an induction heating
coil, and the work piece to be heated. The induction heating coil is typically made of copper tubing or
wire and is shaped to match the geometry of the work piece. The power supply generates high-
frequency alternating current, typically in the range of 1 kHz to 1 MHz, to induce the desired heating
effect.
Applications:
 Metal Fabrication: Induction heating is widely used in metal fabrication processes such as
welding, brazing, soldering, and annealing. It provides precise and localized heating, allowing for
controlled heating of specific areas of the work piece.
INDUCTION HEATING

12.  Heat Treatment: Induction heating is used for heat treatment processes such as hardening,
tempering, and annealing of metals. It enables rapid heating and cooling rates, resulting in
improved material properties and performance.
 Forging and Forming: Induction heating is employed in forging and forming processes to heat
metal billets and blanks to forging temperature, facilitating deformation and shaping of the
material.
 Advantages:
 Rapid Heating: Induction heating allows for rapid heating rates, reducing heating cycle times and
increasing productivity.
 Energy Efficiency: Induction heating is an efficient heating method, with minimal energy loss
compared to other heating processes such as resistance heating or flame heating.
 Clean and Controllable: Induction heating produces clean and controllable heat without the need
for direct contact between the heating element and the workpiece, minimizing contamination and
distortion.
 Limitations:
 Material Limitations: Induction heating is only effective for heating electrically conductive
materials such as metals. Non-conductive materials cannot be heated using this method.
 Initial Investment: Induction heating equipment can be expensive to purchase and install,
particularly for large-scale industrial applications. However, the long-term cost savings from
increased efficiency and productivity may justify the investment.
INDUCTION HEATING

13. Eddy currents play a crucial role in magnetic levitation (maglev) systems, contributing to the
stabilization and control of levitated objects. Here's an overview of eddy currents' role in
magnetic levitation systems:
 Principle:
Magnetic levitation systems utilize electromagnetic forces to suspend and stabilize objects in
mid-air without physical contact. These systems typically consist of electromagnets, permanent
magnets, and control systems to generate and control magnetic fields.
 Levitation Mechanism:
In a maglev system, eddy currents are induced in the levitated object (e.g., a train or a vehicle) as
it moves relative to the magnetic field. These eddy currents generate their own magnetic fields,
which interact with the magnetic field produced by the electromagnets or permanent magnets in
the system. The interaction between the magnetic fields creates a repulsive force that opposes the
gravitational force acting on the object, allowing it to levitate.
 Stabilization and Control:
Eddy currents contribute to the stabilization and control of the levitated object by providing
damping and stability. As the object moves or tilts, changes in the magnetic field induce eddy
currents in the object, which in turn generate additional magnetic fields that interact with the
original magnetic field. These interactions create damping forces that resist the motion of the
object, helping to stabilize it and maintain its position.
MAGNETIC LEVITATION (MAGLEV)

14.  Dynamic Response:
Eddy currents also affect the dynamic response of the levitated object to external
disturbances, such as wind or vibrations. The induced currents and resulting magnetic
fields provide a damping effect that dampens oscillations and vibrations, enhancing
the stability and ride quality of the maglev system.
 Efficiency and Energy Consumption:
While eddy currents contribute to the stabilization and control of maglev systems, they
can also result in energy losses and increased power consumption due to the
generation of heat. Therefore, efficient control algorithms and magnetic field designs
are necessary to minimize energy losses and optimize the performance of the system.
Overall, eddy currents play a vital role in magnetic levitation systems by contributing
to the stabilization, control, and dynamic response of levitated objects. Understanding
and harnessing the effects of eddy currents are essential for the development and
operation of efficient and reliable maglev systems.
MAGNETIC LEVITATION (MAGLEV)

15. In addition to the applications already mentioned, such as Non-Destructive Testing (NDT), Eddy
Current Braking, Eddy Current Separators, Induction Heating, and Magnetic Levitation, there are
several other applications of eddy currents. Here are some additional examples:
 Proximity Sensors:
Eddy currents are utilized in proximity sensors to detect the presence or proximity of metallic objects
without physical contact. When a conductive object approaches the sensor, it induces eddy currents in
the sensor, causing changes in impedance or resonant frequency, which are then detected and used to
determine the object's proximity.
 Metal Sorting and Recycling:
Eddy currents are employed in metal sorting and recycling systems to separate different types of
metals based on their conductivity and magnetic properties. By inducing eddy currents in metallic
objects, it is possible to sort and separate them from non-metallic materials, facilitating recycling and
resource recovery.
 Eddy Current Dynamometers:
Eddy current dynamometers are used for measuring torque and power in rotating machinery such as
engines, motors, and turbines. These dynamometers utilize the interaction between a rotating
conductive disc and a magnetic field to generate eddy currents, which produce a braking force
proportional to the torque being measured.
APPLICATIONS OF EDDY CURRENT

16.  Eddy Current Clutches:
Eddy current clutches are used in automotive, industrial, and marine applications to transmit torque
between two rotating shafts without physical contact. These clutches utilize the interaction between a
rotating conductive disc and a magnetic field to generate eddy currents, which produce a braking force
that controls the torque transfer between the shafts.
 Eddy Current Displacement Sensors:
Eddy current displacement sensors are used for non-contact measurement of displacement, position, or
thickness in various applications. These sensors utilize the interaction between an oscillating magnetic
field and a conductive target to induce eddy currents, which produce changes in impedance or phase
shift that are proportional to the displacement being measured.
 Eddy Current Tube Testing:
Eddy current tube testing is used for inspecting heat exchanger tubes, boiler tubes, and other tubular
structures for defects such as corrosion, erosion, and wall thinning. This technique utilizes the
interaction between an eddy current probe and the conductive tube material to detect changes in
conductivity or impedance caused by defects in the tube wall.
APPLICATIONS OF EDDY CURRENT

17. REFERENCES
1. Israel D. Vagner; B.I. Lembrikov; Peter Rudolf Wyder (17 November 2003). Electrodynamics of
Magnetoactive Media. Springer Science & Business Media. pp. 73–. ISBN 978-3-540-43694-2.
2. Walt Boyes (25 November 2009). Instrumentation Reference Book. Butterworth-Heinemann. pp.
570–. ISBN 978-0-08-094188-2.
3. Howard Johnson; Howard W. Johnson; Martin Graham (2003). High-speed Signal Propagation:
Advanced Black Magic. Prentice Hall Professional. pp. 80–. ISBN 978-0-13-084408-8.
4. F. Fiorillo, Measurement and Characterization of Magnetic Materials, Elsevier Academic Press,
2004, ISBN 0-12-257251-3, page. 31
5. Wangsness, Roald. Electromagnetic Fields (2nd ed.). pp. 387–8.
6. G. Hysteresis in Magnetism: For Physicists, Materials Scientists, and Engineers, San Diego:
Academic Press, 1998.
7. Archived at Ghostarchive and the Wayback Machine: "Eddy Current Tubes". YouTube.

18. THANK YOU