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. However, unlike electro-mechanical brakes, in which the drag force used to stop the moving object is provided by friction between two surfaces pressed together, in an eddy current brake the drag force is an electromagnetic force between a magnet and a nearby conductive object in relative motion, due to eddy currents induced in the conductor through electromagnetic induction. A conductive surface moving past a stationary magnet will have circular electric currents called eddy currents induced in it by the magnetic field, due to Faraday's law of induction. By Lenz's law, the circulating currents will create their own magnetic field which opposes the field of the magnet. Thus the moving conductor will experience a drag force from the magnet that opposes its motion, proportional to its velocity. The electrical energy of the eddy currents is dissipated as heat due to the electrical resistance of the conductor. In an electromagnetic brake the magnetic field may be created by a permanent magnet, or anelectromagnet so the braking force can be turned on and off or varied by varying the electric current in the electromagnet's windings. Another advantage is that since the brake does not work by friction, there are no brake shoe surfaces to wear out, necessitating replacement, as with friction brakes. A disadvantage is that since the braking force is proportional to velocity the brake has no holding force when the moving object is stationary, as is provided by static friction in a friction brake, so in vehicles it must be supplemented by a friction brake. Eddy current brakes are used to slow high-speed trains and roller coasters, to stop powered tools quickly when power is turned off, and in electric meters used by electric utilities.

1. DEPARTMENT OF ELECTRICAL ENGINEERING
Seminar On
GuidedBy: Presentedby :
Mrs.y.sunusha Mr. karthik.potla
Department of Electrical Engg B.Tech IVth Year

2. Contents
Introduction of Eddy Current
Eddy Current Brakes
Need of Eddy Current Braking
Difference Between Electromechanical & Eddy Current Brake
Principle Involved
Construction
Parameter of construction
Working principle
Types of Eddy Current Brakes
Applications
Advantages & Disadvantages

3. Definition → When a rotating conductor is moved in a
magnetic field a motional emf is generated. This emf
drives a current. The induced currents which circulate
inside a moving conductor are usually called eddy
currents.
Have inductance and thus induce magnetic fields.
Cause repulsion, attraction, heating effects etc.

4. Eddy Current Brakes
• Makes use of the opposing
tendency of eddy currents
to inhibit the motion of a
mechanical system.

5. Need for a braking system.

6. Abrasion Free
• No use of mechanical blocking, so there is no high levels of wear and tear & the life
of systems remains same.
Eco friendly
• No use of brake pad which produces debris.
High Braking Force
• This produces high braking forces to inhibit system.

7. How are eddy current brakes different from
electromagnetic brakes ?
Eddy Current Brakes
• Uses magnetic force.
• There is an air gap present to
prevent mechanical transmission
of torque.
Electro-magnetic brakes
• Uses electromagnetic circuit and
hence ultimately use frictional force.
• There is a mechanical linkage to
transmit torque.

8. Principle involved

9. Principle involved
• Faraday’s law of Electromagnetic Induction
The induced electromotive force in any closed circuit is equal to the negative of the time rate
of change of the magnetic flux through the circuit.
𝛆 = −𝐍
𝐝∅ 𝐁
𝐝𝐭
Where
 is EMF (Volts)
B is Magnetic Flux (Webers)
 is number of turns of wire

10. Principle involved
Lenz’s Law :
An induced emf always gives rise to a current whose magnetic
field oppose the Change in magnetic flux.
Where
ΦB is magnetic flux (Weber)
ε is emf (volts)

11. Construction
• A stationary magnetic field
• A solid rotatory disc
An eddy current brake basically consists of two members:

12. Parameters of Construction
PARAMETERS
Current
induced
Disc
material &
thickness
Turns
Air gap

13. Working Principle
During braking, the metal disc is exposed to
a magnetic field from an electromagnet,
generated eddy current 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.

14. Types of Eddy Current Brakes
Circular eddy current brake
Linear eddy current brake
1.
2.

15. Applications
Trains
Motor
test
stands
Applicati
ons
Row
ing
mac
hine
s
Roller
coaster
Free fall
tower
rides

16. ADVANTAGES DISADVANTAGES
therefore no wear
or tear.
 No noise or
smell.
 Adjustable
brake force.
 High brake
forces at high
speeds.
Braking force
diminishes as speed
diminishes.
It can not be used
for low speed
vehicles .