DEPARTMENT OF ELECTRICAL ENGINEERING

Seminar On

Guided By: Presented by :Mrs.y.sunusha Mr. karthik.potla

Department of Electrical Engg B.Tech IVth Year

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

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.

Eddy Current Brakes

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

Need for a braking system.

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.

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.

Principle involved

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 = −𝐍𝐝∅𝐁𝐝𝐭

Where

is EMF (Volts)

B is Magnetic Flux (Webers)

is number of turns of wire

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)

Construction

• A stationary magnetic field

• A solid rotatory disc

An eddy current brake basically consists of two members:

Parameters of Construction

PARAMETERS

Current induced

Disc material & thickness

Turns

Air gap

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.

Types of Eddy Current Brakes

Circular eddy current brake

Linear eddy current brake

1.

2.

Applications

Trains

Motor test

stands

Applications

Rowing

machine

s

Roller coaster

Free fall tower rides

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 .