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.
• To read more about skin effect follow the below
  given website link.
• www.electricalride.com