09-05-2014, 02:02 PM
INTRODUCTION Of Eddy Current
Eddy Current.ppt (Size: 1.36 MB / Downloads: 17)
INTRODUCTION
Eddy currents (Foucault currents) are electric currents induced in conductors when exposed to a changing magnetic field; due to relative motion of the field source and conductor or due to variations of the field with time.
This can cause a circulating flow of
electrons, or current, within
the body of the conductor.
These circulating eddies
of current have inductance and thus induce magnetic fields.
circular eddy current brake system
Electromagnetic brakes are similar to electrical motors;
non-ferromagnetic metal discs (rotors) are connected to a rotating coil, and a magnetic field between the rotor and the coil creates a resistance used to generate electricity or heat.
When electromagnets are used, control of the braking action is made possible by varying the strength of the magnetic field.
A braking force is possible when electric current is passed through the electromagnets.
The movement of the metal through the magnetic field of the electromagnets creates eddy currents in the discs.
LINEAR EDDY CURRENT BRAKE
The principle of the linear eddy current brake has been described by the French physicist Foucault.
The linear eddy current brake consists of a magnetic yoke with electrical coils positioned along the rail, which are being magnetized alternating as south and north magnetic poles.
This magnet does not touch the rail, as with the magnetic brake, but is held at a constant small distance from the rail (approximately seven mm).
When the magnet is moved along the rail, it generates a non-stationary magnetic field in the head of the rail, which then generates electrical tension (Faraday's induction law), and causes eddy currents.
These disturb the magnetic field in such a way that the magnetic force is diverted to the opposite of the direction of the movement, thus creating a horizontal force component, which works against the movement of the magnet.