1. DC MOTORS T

2. TOPICS TO DISCUSS Introduction to DC MOTORS. Principle. Construction.
Working.
Types.
Speed control.
Applications.

3. DC MOTOR
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.

4. 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.

5. CONSTRUCTION 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.

7. WORKING OF DC MOTORS

8. TYPES OF DC MOTORS DC motor are of 3 types they are….. DC SHUNT MOTOR
DC SERIES MOTOR
DC COMPOUND MOTOR

9. 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.
Armature

10. 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.

11. 3. DC COMPOUND MOTOR DC COMPOUND MOTOR LONG SHUNT COMPOUND MOTOR
SHORT SHUNT COMPOUND MOTOR
CUMULATIVE COMPOUND MOTOR
DIFFERENTIAL COMPOUND MOTOR

12. 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.

13. 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.

14. CUMULATIVE 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
DIFFERENTIAL COMPOUND DC MOTORS
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.

15. METHODS OF SPEED CONTROL
1. FLUX CONTROL—
Speed of dc motor is inversely
prop. to field flux
So speed can be controlled above base speed
It is constant power speed control.
Speed below base speed is not possible in this method.

16. METHODS OF SPEED CONTROL
2. ARMATURE VOLTAGE CONTROL-
Speed of dc machine is directly prop. to armature voltage.
So speed below base speed can be controlled.
It is a constant torque method.
Speed reversal is possible.

17. APPLICATIONS OF DC MOTORS
D.C. SHUNT MOTOR
LATHES , FANS, PUMPS DISC AND BAND SAW DRIVE REQUIRING MODERATE TORQUES.
D.C. SERIES MOTOR
ELECTRIC TRACTION, HIGH SPEED TOOLS
D.C. COMPOUND MOTOR
ROLLING MILLS AND OTHER LOADS REQUIRING LARGE MOMENTARY TORQUES.

18. THANK YOU