eddy

1. Presented By :~
Vikram Vijayant Rana

2. Contents :~
 Introduction of eddy current
 Introduction of eddy current brake
 Circular eddy current brake
 Linear eddy current brake
 How eddy current brake works?
 Advantages
 Disadvantages
 Applications
 Future Aspects
 conclusion

3. 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.

4. Š Eddy current brakes, like conventional friction brakes, are
responsible for slowing an object, such as rotating
machinery, a moving train, or even a roller coaster
ŠThere are two basic types: (1)rotational
(2)linear

5. 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.

6.  These eddy currents generate an opposing magnetic field (Lenz's
law), which then resists the rotation of the discs, providing braking
force.
 The net result is to convert the motion of the rotors into heat in the
rotors.
 Japanese Shinkansen trains had employed circular eddy current
brake system on trailer cars since 100 Series Shinkansen.

7. 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.

8.  The braking energy of the vehicle is converted in eddy current losses which
lead to a warming of the rail. (The regular magnetic brake, in wide use in
railways, exerts its braking force by friction with the rail, which also creates
heat.)
 The eddy current brake does not have any mechanical contact with the rail, and
thus no wear, and creates no noise or odor.
 The eddy current brake is unusable at low speeds, but can be used at high
speeds both for emergency braking and for regular braking.
 The first train in commercial circulation to use such a braking system has been
the ICE 3.
 Modern roller coasters also use this type of braking, but in order to avoid the
risk of potential power outages, they utilize permanent magnets instead of
electromagnets , thus not requiring any power supply.

11. Working Principle

12. Magnetic field lines across the
magnetic material inside a copper tube

13. Direction of magnetic lines of force due
to magnet in copper tube

18. (Arrangement of ECB between train wheels)

19. (Arrangement of ECB in high speed trains)

20. ADVANTAGES:~
Independent of wheel/rail adhesion.
No contact, therefore no wear or tear.
No noise or smell.
Adjustable brake force.
High brake forces at high speeds.
Used also as service brake.
It uses electromagnetic force and not friction
Non-mechanical (no moving parts, no friction)
Can be activated at will via electrical signal
Low maintenance
Light weight

21. DISADVANTAGES:-~
Braking force diminishes as speed
diminishes with no ability to hold the load
in position at standstill.
It can not be used at low speed vehicles or
vehicle running at low speed.
ECB is used with ordinary mechanical
brakes.
Nowdays ECB is using only for safety
purpose.

22. Applications:~
It is used as a stopping mechanism in
trains.
It is also used in the smooth breaking and
functioning of roller coasters and such fast
moving machines.

23. FUTURE ASPECT:-~
 In future ordinary brakes will be replaced
by the ECB completely.
 By the use of ECB in future we can
control high speed train completely.
 By some new invention of extra
mechanism we can use ECB for slow
speed vehicles also.

24. CONCLUSION;~
 ECB is a good invention for the speed
control of high speed vehicles
 We can control the speed of high speed
vehicles without wear and tear in parts
of it.
 Drawback of ordinary mechanical
braking system can be overcome by
application of ECB.
 It makes use of opposing tendency
of eddy current.