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In electromagnetism, an eddy current (also called Foucault's current) is a loop of electric current induced within conductors by a changing magnetic field in the conductor according to Faraday's law of induction or by the relative motion of a conductor in a magnetic field. Eddy currents flow in closed loops within conductors, in planes ...
Skin depth depends on the frequency of the alternating current; as frequency increases, current flow becomes more concentrated near the surface, resulting in less skin depth. Skin effect reduces the effective cross-section of the conductor and thus increases its effective resistance. At 60 Hz in copper, skin depth is about 8.5 mm. At high ...
These are called eddy currents. On the lefthand side nearest to the other wire (1) the eddy current is in the opposite direction to the main current (big pink arrow) in the wire, so it subtracts from the main current, reducing it. On the righthand side (2) the eddy current is in the same direction as the main current so it adds to it ...
Eddy currents flow in closed loops in planes perpendicular to the magnetic field. They have useful applications in eddy current brakes and induction heating systems. However eddy currents induced in the metal magnetic cores of transformers and AC motors and generators are undesirable since they dissipate energy (called core losses) as heat in ...
However, since the inductive impedance increases proportionally with frequency, so does the EMF, so the current tends to a limit when the resistance is small relative to the inductive impedance. This also limits the lift force. Power used for levitation is therefore largely constant with frequency.
an increase of the gap reduces the ratio of the total loss to the reactive power, with the limiting factor being the increased heating due to the copper loss. The total gap is frequently made of a series of small gaps to limit the effect of eddy currents in the core. [5]
The AC current in the electric coil generates eddy current on the surface of the material. According to the theory of electromagnetic induction, the distribution of the eddy current is only at a very thin layer of the material, called skin depth. This depth reduces with the increase of AC frequency, the material conductivity, and permeability.
Eddy Current Testing at Level 2, International Atomic Energy Agency, Vienna, 2011 (pdf 5.6 MB). ASTM E3052 Standard Practice for Examination of Carbon Steel Welds Using Eddy Current Array Official web page of Lorentz Force Velocimetry and Lorentz Force Eddy Current Testing Group Archived 2013-11-17 at the Wayback Machine