EDDY CURRENT

1. PRESENTED BY:-
NAME- RAHUL KUMAR
ROLL NO:- 125069
REGD NO:- 1201211280
GUIDED BY:-
ER.DEBASHISH MISHRA
ASST. PROFESSOR
DEPARTMENT OF
ELECTRICAL ENGG.

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 current is the swirling
current produced in a
conductor which is
subjected to change in
magnetic field.
 Because of the tendency of
the eddy current to
oppose,it causes energy to
be lost.
 More accurately it converts
more useful energy, such
as kinetic energy in to heat.
 Practically its not desirable

4. EDDY CURRENT BRAKING….
 These are simple magnetic
devices that consists of non
ferromagnetic conductor that
moves through a magnetic
field.
 An example is shown in fig.
where magnetic field is
created in the gap of a
torroidal magnet with
diameter =D
When a conductive disc rotates
eddy current is induced at a
average distance R from axis
of rotation.
 Poles magnetic field moves
as a function of angular
velocity of the disc,

5. Contd……
 Power is dissipated in the disc by the
joules effect which causes a viscous like
torque applied to disc….

6. Principle of operation…
 It works according to faraday’s law of
electromagnetic induction
 According to this law when ever a conductor
cuts magnetic lines of forces a emf is induced in
it…..
emf. magnitude α strength of magnetic field
α speed of the conductor
 If the conductor is a disc then it will be a
circulatory current i.e. eddy current in the disc.

7. Contd….
 According to lenz’s law the direction of
current is in such a way that it opposes
the very cause producing it i.e
movement of the disc..
 Since wheels are directly coupled to
discs, thus producing smooth braking.
 Key equation: induced emf = -N dϕ/dt

8. Theoretical foundation…..
 If the rotating metallic disc is subjected to magnetic field
present in the gap of the electromagnet.
 Eddy current appear inside the disc and breaks its rotation
the approximate expression for the power dissipated by
eddy current is…..
B = steady electric field
V= velocity of the disc
induced electric field (E) = V×B
replacing B by excitation current “Iex” in the coils of
electromagnet, we have
E α ωIex
where, ω = angular velocity of the disc
 Power dissipated in the disc is proportional to the square of
emf and to the inverse of electrical resistivity.

9. 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.

10. Braking time of the disc…..
 Time is necessary for the
disc to completely stop
from initial angular speed.it
can be measured as a
function of excitation
intensity.
 Larger excitation intensity
makes braking time
shorter as a result of more
powerful eddy currents.

11.  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.

12. 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.

13.  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.

15. (Arrangement of ECB in high speed trains)

16. 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

17. 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.
Nowadays ECB is using only for safety
purpose.

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

19. 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.

20. 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.

21. THANK YOU