Abstract :
Many of the
ordinary brakes, which are being used now days stop the vehicle by means of
mechanical blocking. This causes skidding and wear and tear of the vehicle. And
if the speed of the vehicle is very high, the brake cannot provide that much
high braking force and it will cause problems. These drawbacks of ordinary
brakes can be overcome by a simple and effective mechanism of braking system
‘The eddy current brake’. It is an abrasion-free method for braking of vehicles
including trains. It makes use of the opposing tendency of eddy current.
Eddy current is the swirling current produced
in a conductor, which is subjected to a change in magnetic field. Because of
the tendency of eddy currents to oppose, eddy currents cause energy to be lost.
More accurately, eddy currents transform more useful forms of energy such as
kinetic energy into heat, which is much less useful. In many applications, the
loss of useful energy is not particularly desirable. But there are some
practical applications. Such an application is the eddy current brake.
PRINCIPLE
OF OPERATIONS
Eddy
current brake works according to Faraday’s law of electromagnetic induction.
According to this law, whenever a conductor cuts magnetic lines of forces, an
emf is induced in the conductor, the magnitude of which is proportional to the
strength of magnetic field and the speed of the conductor. If the conductor is
a disc, there will be circulatory currents i.e. eddy currents in the disc.
According to Lenz’s law, the direction of the current is in such a way as to
oppose the cause, i.e. movement of the disc.
Essentially the eddy current brake consists of
two parts, a stationary magnetic field system and a solid rotating part, which
include a metal disc. During braking, the metal disc is exposed to a magnetic
field from an electromagnet, generating eddy currents in the disc. The magnetic
interaction between the applied field and the eddy currents slow down the
rotating disc. Thus the wheels of the vehicle also slow down since the wheels
are directly coupled to the disc of the eddy current brake, thus producing
smooth stopping motion.
Download :
Download :