• Presenter…

-Sumeet Patel (99)

DC MOTORS

TOPICS TO DISCUSS

Introduction to DC MOTORS.

Principle.

Construction.

Working.

Types.

Applications.

• A DC motor or Direct Current Motor converts electrical energy into mechanical energy.

• A direct current (DC) motor is a fairly simple electric motor that uses electricity and a magnetic field to produce torque, which turns the rotor and hence give mechanical work.

DC MOTOR

PRINCIPLE OF DC MOTORS

• In any electric motor, operation is based on simple electromagnetism.

• When a current-carrying conductor is placed in an external magnetic field, it will experience a force i.e. Lorentz force.

• Due to this force torque is produced which rotates the rotor of motor and hence a motor runs.

• DC motor consist of 2 windings…

1. Field winding.

2. Armature winding.

• Field winding is stationary and armature winding can rotate freely.

• Field windings when given DC supply, magnetic field is produced.

• Armature winding when connected to DC source, shaft connected to it rotates due to Lorentz force.

CONSTRUCTION

WORKING OF DC MOTORS

TYPES OF DC MOTORS

• DC motor are of 3 types they are…..

1. DC SHUNT MOTOR

2. DC SERIES MOTOR

3. DC COMPOUND MOTOR

1. DC SHUNT MOTOR

Armature

• The parallel combination of two windings is connected across a common dc power supply.

• The resistance of shunt field winding (Rsh) is always higher than that is armature winding.

• This is because the number of turns for the field winding is more than that of armature winding.

• The cross-sectional area of the wire used for field winding is smaller than that of the wire used for armature winding.

2. DC SERIES MOTOR

• The field winding is connected in series with the armature.

• The current passing through the series winding is same as the armature current .

• Therefore the series field winding has fewer turns of thick wire than the shunt field winding.

• Also therefore the field winding will posses a low resistance then the armature winding.

3. DC COMPOUND MOTOR

DC COMPOUND

MOTOR

LONG SHUNT COMPOUND

MOTOR

SHORT SHUNT COMPOUND

MOTOR

CUMULATIVE COMPOUND

MOTOR

DIFFERENTIAL COMPOUND

MOTOR

I. LONG SHUNT COMPOUND MOTOR

• In this the series winding is connected in series with the armature winding and the shunt winding is connected in parallel with the armature connection.

II. SHORT SHUNT COMPUND MOTOR

• In short shunt compound motor the series winding is connected in series to the parallel combination of armature and the shunt winding

• This is done to get good starting torque and constant speed characteristics.

a) CUMULATIVE COMPOUND DC MOTORS

b) DIFFERENTIAL COMPOUND DC MOTORS

• If the two field windings i.e. series and shunt are wounded in such a way that the fluxes produced by them add or assist each other

• If the two field winding i.e. series and shunt are wounded in such a way that the fluxes produced by them always try to oppose and try to cancel each other.

APPLICATIONS OF DC MOTORS

MOTORS.. APPLICATIONS…

D.C. SHUNT MOTORLATHES , FANS, PUMPS DISC AND BAND SAW DRIVE REQUIRING MODERATE TORQUES.

D.C. SERIES MOTOR ELECTRIC TRACTION, HIGH SPEED TOOLS

D.C. COMPOUND MOTORROLLING MILLS AND OTHER LOADS REQUIRING LARGE MOMENTARY TORQUES.

BIBLIOGRAPHY

www.google.com

en.wikipedia.org

Electrical technology –B.L. Theraja–A.K. Theraja

ANY QUESTIONS ???