3. INTRODUCTION
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
4. An eddy current brake, like a conventional friction brake, is a device used
to slow or stop a moving object by dissipating its kinetic energy as heat.
In an eddy current brake the magnetic field may be created by a
permanent magnet, or an electromagnet so the braking force can be
turned on and off or varied by varying the electric current in the
electromagnet's windings.
5. PRINCIPLE
Faraday’s Law of Electromagnetic Induction
The induced electromotive force at any closed circuit is equal to the negative of
the time rate of change of the magnetic flux through the circuit.
Where
• E is EMF
• Φ is Magnetic flux
• N is Number of turns of wire
E= -N dΦ/dt
6. Lenz’s Law
An induced emf always gives rise to a current whose magnetic field opposite the
change in magnetic flux.
Where
• E is EMF
• Φ is Magnetic Flux
E= -dΦ/dt
8. Electromagnets produce Primary magnetic field from
supplied current which in turn produces eddy current.
Eddy Current produces secondary magnetic field which
opposes the primary field.
Opposing magnetic field reduces the Velocity
9. TYPES
Circular:- In a circular eddy current brakes, the
conductor is a flat disk rotor that turns between the
poles of the magnet.
10. Linear :- In a linear eddy current brakes, the conductive
piece is a straight rail or track that the magnet moves along.
11. ADVANTAGES
Wide range of braking force available within the temperature limit
Smooth retardation
Non-mechanical ( no moving parts, no friction )
Can be simply activated at will via electrical signal
Low maintenance
Operates at any rotational speed
Light weight
Eddy-current brakes are quite, frictionless, and wear-free, and require
little or no maintenance.
They produce no smell or pollution ( unlike friction brakes, which can
release toxic chemicals into the environment ).
12. DISADVANTAGES
Braking force diminishes as speed diminishes with no ability to
hold the load in position at standstill.
Need of electric power.
That could be considered to be a safety issue, but it really
means that friction braking may need to be used as well.
Eddy-current brakes can only be used where the infrastructure
has been modified to accept them.
It can not be used at low speed vehicles or vehicle running at
low speed
13. APPLICATIONS
For additional safety on long decants in mountain area.
For high speed passenger and goods vehicle.
Eddy current brakes are best substitutes for ordinary brakes,
which are being used nowadays in road vehicles even in trains,
because of their jerk-free operation.
In mountain areas where continuous braking force is needed,
for a long time, the eddy current braking is very much useful
for working without overheating.
It can also be used to slow down the trolleys of faster roller
coasters.
To stop the powered tools
14. CONCLUSION
The ordinary brakes which are being used now a days stop the
vehicles by means of mechanical blocking. These may cause
skidding and wear and tear of the vehicle.
Eddy Current Brakes is a good invention for speed control of
high speed vehicles.
It is an abrasion free method for braking of vehicle including
trains.
It makes use of opposite tendency of eddy currents.
