This presentation is about the whole pricipal about DC machine. It explain the various important parts of dc machine.It tells about how many types of losses are present in DC machine.

1. Presented By
Premchand Kumar

2.  A electro mechanical energy conversion device.
 The rotating electrical or DC machine has mainly
two parts; one is Stator, and another one is Rotor.
 Slots are cut on the inner periphery of stator and
outer periphery of Rotor.

4.  It supports the pole core.
 Act as a Protecting cover to the machine

5. The pole shoe serves two purpose:-
 It supports the field coils.
 It spread out the flux in air gap uniformly.

6.  Forms an electromagnet.
 Produces field flux within which the armature
conductor of the DC machine rotates, and results in
the effective flux cutting.

7.  The rotating part of the DC machine is called the
armature.
 Armature core includes the huge number of slots
within its edge.
 Armature conductor is located in these slots.

9.  The basic purpose of commutator in DC machine to
convert the AC TO DC AND DC TO AC.
 Brushes in the DC machine gather the current from
commutator and supplies it to exterior load.

10. DC
Machine
DC
Generator
Converts Mechanical
Energy into
Electrical Energy
DC Motor
Converts Electrical
Energy into
Mechanical Energy

11.  According to the Faraday’s Law of electromagnetic
induction whenever a conductor is placed in a
varying magnetic field (OR a conductor is moved in
a magnetic field), an EMF (electromotive force) gets
induced in the conductor.
 If the conductor is provided with a closed path, the
induced current will circulate within the path.
 The direction of induced current is given by
Fleming’s right hand rule.

13.  whenever a current carrying conductor is placed in
a magnetic field, it experiences a mechanical force.
 The direction of this force is given by Fleming's left
hand rule.
 its magnitude is given by F = BIL.
 Where, B = magnetic flux density, I = current and
L = length of the conductor within the magnetic
field.

14. DC
Machine
Self
Excited
Shunt
Excited
Series
Excited
Compound
Machine
Separately
Excited

17.  E= (nPΦZ)/A
 Where n= Speed of rotation armature in revolution
per second.
P= No. of Poles
Φ= Flux per pole
Z= No. of conductor
A= No of Parallel path

21. Losses
Copper
Loss
Core Loss
Stray Load
Loss
Mechanical
Losses

22. Copper Loss
Armature
loss
Field
winding
loss
Core Losses
Hysteresis
loss
Eddy
current loss

23. Generator Action
Shaft Power
-Rotational Losses
Armature Power
-Copper Losses
Electrical Power at
Terminals
Motor Action
Electrical Power at
Terminals
-Copper Losses
Armature Power
-Rotational Losses
Shaft Power

24. Speed Control
Armature
Resistance
Control
Field Flux Control
Ward Leonard
Method

25.  The speed of the DC motor is directly proportional
to the back EMF (Eb).
 When supply voltage (V) and armature resistance
(Ra) are kept constant, the Speed is directly
proportional to armature current (Ia).
 If we add resistance in series with the armature, the
armature current (Ia) decreases and hence speed
decreases.

26.  Speed of the motor is inversely proportional to the
flux.
 External resistance is inserted in series with the
field winding.
 Speed can be controlled only above base speed.

27.  Advantage
o Wide range and smooth speed control
o Speed regulation is quite good
o Efficiency at low speeds is higher.
 Disadvantage
o Higher initial cost

28. Electrical
Braking
Regenerative
Braking
Dynamic
Braking
Reverse
Current Braking

29.  When applied voltage to the motor is reduced to less
than back emf Eb, obviously armature current Ia will
get reversed, and hence armature torque is
reversed. Thus speed falls.

32. Types of
Testing
Swinburne’s
Test
Hopkinson’s
Test

33.  In this test the efficiency of the machine at any load
is pre-determined.
 We can run the machine as a motor or as a
generator.

34. Advantages of Swinburne’s Test
 Very convenient and economical.
 efficiency of Swinburne’s test can be pre-
determined at any load.
Disadvantages of Swinburne’s Test
 We can’t measure the temperature rise when the
machine is loaded.
 In DC series motor, the Swinburne’s test cannot be
done to find its efficiency as it is a no load test.

35.  Machine-1 running as a motor drives the machine-
11 as a generator.
 The Power of Generator is fed to the motor.
 The speed of set should be equal to the rated speed.

36. Advantages of Hopkinson’s Test
 Efficiency at different loads can be determined.
 Temperature rise can be checked under rated
condition.
Disadvantages of Hopkinson’s Test
 It is not possible to get separate iron losses for the
two machines though they are different because of
their excitations.
 Both machines cannot be loaded equally all the time.

37.  Current Rating
 Voltage Rating
 Power Rating
 Speed Rating
 Temperature

38.  Series Motors:- Where high starting torque is
required and speed can be vary. For Ex:- Traction,
Cranes, etc.
 Shunt Motors:- Where constant speed is required
and starting condition are not severe. For Ex:-
Centrifugal Pumps, Blowers, Conveyors, Lift, etc.
 Compound Motors:-Where starting torque is high
and fairly constant speed is required. For Ex:-
Elevators, Shears, Rolling Mills, etc.