# What is eddy Current ? - PowerPoint PPT Presentation

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## What is eddy Current ?

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Title: What is eddy Current ?

1
EDDY CURRENT
• Electrical eddy current is the current that
originates within the current carrying conductor
by changing magnetic field due to Faraday's law
of induction.
• Eddy current circulates in a closed loop within
the conductor, perpendicular to the magnetic
field that generates it. It may generate when a
conductor is exposing to magnetic field or when a
moving magnetic field gets closer to a stationary
metallic conductor.

2
• "Anything that changes the direction and
intensity of magnetic field induces eddy current
in conductor
• The value of current induces is directly
proportional to loop area, magnetic field
strength and rate of change of flux while
inversely proportional to the material
resistivity.

3
HOW DOES EDDY CURRENT PRODUCE?
• As we know that in magnetic field, charged
particles experience a force. There are so many
free electrons in conductive materials that move
around within the material. As these electron's
experiences a force due to change of magnetic
flux within magnetic field, creates circular
electric field perpendicular to that magnetic
field. This electric field produces a flow of
current in small loop, which is eddy current.

4
WHAT DOES EDDY CURRENT DO?
• Lenz's law states that, as the induced eddy
current flows, it will originate its own magnetic
field. The direction of this magnetic field will
be such that it opposes the external magnetic
field. Thus, eddy current reduces the overall
magnetic field. This property of reducing overall
magnetic field is useful for stopping rotating
power tools. Thus, eddy current causes energy
loss in alternating current operating machinery.

5
LIMITING EDDY CURRENT
• Metallic conductors are sliced into thin metal
sheets to reduce eddy current. This reduces the
surface area of conductor resulting in lowering
eddy current loss. This phenomenon is adopted in
transformer manufacturing world widely.
Transformer cores are cut into thin sheets. These
sheets are then laminated with insulator in
between them to limit induced magnetic field.
Thus result in limiting transformer iron core
loss and heating loss.

6
APPLICATION OF EDDY CURRENT
• Eddy current also has advantages up to some
extinct. It can be useful to diagnose cracks
within the conductors. Since cracks within
conductive material prevents formation of loops
in that region thus resulting in detecting
defects in materials. This is called
nondestructive testing (NDT) and is often use to
test airplane surfaces.

7
• It can also be useful for braking purposes. As
mentioned above, it can be helpful in quickly
turning kinetic energy into other form of energy.
• Another application of eddy current is its use
in certain type of proximity sensors to observe
the vibration and function of rotating shafts
inside their bearings. Those sensors are
extremely sensitive to very small displacements
making them well suitable to examine the minute
vibrations in turbo-machinery

8
• It can be useful for the identification of coins.
The coin rolls beyond a stationary magnet, and
eddy currents slow its pace. The eddy currents
strength and thus the retardation, relies upon at
the conductivity of the coin's metal. Slug coins
behave differently than genuine coins.

9
• Eddy current is also responsible for skin effect
in high voltage conductors.