STUDY OF DIFFERENT TYPES OF D.C MOTORS

1

• STUDY OF DIFFERENT TYPES OF D.C MOTORS
• PRESESNTATION BY
• 
  Harpreet Singh
• 
  Lecturer
• G.P.C
  Mohali

2
DC MACHINES
FIELD WINDING
YOKE
S
BRUSH AXIS
ARMATURE
_


BRUSH
ARMATURE CONDUCTORS
FIELD POLES
N
MAIN FIELD AXIS
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
LECTURE 5 OF 40
3
DC MACHINES
?
S
?
( GENERATOR )
?
A
B
_
S
N
MECHANICAL INPUT

?
?
Te
?
?
?
?
?
Tm
ELECTRICAL LOAD
?
?
N
?
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
LECTURE 5 OF 40
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DC MACHINES
?
S
?
( MOTOR )
?
A
B
_
S
N
MECHANICAL LOAD

?
?
Te
?
?
?
?
?
DC SUPPLY
v
TL
?
N
?
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
Electrical machines can be classified mainly into
DC Machines and AC Machines. Slide no 1 shows
the view of a dc machine. For simplicity , only
main component parts have been shown.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The field windings are shown as excited from
external source.The polarity of electro-magnetic
field will depend upon the direction of field
current as shown in the fig. of slide no.1 .
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The armature carries conductors in side the
slots.Two brushes are placed at the right angle
to the main field axis. The brushes are
stationary whereas armature is free to rotate.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
When the armature is rotated in the magnetic
field, an e.m.f will be induced in the armature
conductors.The direction of the induced e.m.f
can be found by applying Flemings Right Hand
Rule.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The direction of induced e.m.f will depend upon
the direction of rotation of armature , if
polarity of field poles to be kept unchanged.When
load is connected across the armature terminals ,
the current will flow through the armature
circuit.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The direction of current will be same as that of
induced e.m.f. The armature will now be
considered as electro-magnet and its polarity is
shown in the fig. of slide no. 2 .The
electro-magnetic torque Te will be developed in
the anti-clock wise direction as shown in the
fig.of slide no. 1 and 2.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The magnitude of Te will depend on the strength
of the field poles and armature field which
further depends upon the currents flowing through
the respective windings. As the external load on
the generator is increased, the magnitude of Te
increases.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
As Te acts in the opposite direction to the
applied mechanical torque, more torque will be
required through the prime mover to maintain the
speed of armature .
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The direction of currents in the upper conductors
in the armature are indicated by dots and
conductors in lower half of armature are
indicated by cross .
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The brush B will collect dot currents and brush
A will collect cross currents as the armature
continues to rotate in clockwise direction. In
the out put circuit, across terminals A and
B, current will flow in one direction.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The dc machine shown in fig. of slide no. 2 is
working as generator.The same machine will work
as motor , if the armature is provided with
electric supply as shown in fig. of slide no. 3
.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The armature is connected across a supply voltage
V and the field windings are excited from the
same supply or from any external dc source.The
magnetic polarities due to the current in
armature winding will be as shown in fig. of
slide no. 3 .
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
The electro-magnetic torque Te will be
developed in the anti-clockwise direction as
opposite poles of armature field and main field
will attract each other. The armature will rotate
in anti-clockwise direction due to Te .
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
To reverse the direction of rotation of armature,
either the direction of current in the field
winding or armature winding will have to be
reversed.If the direction of currents in both the
windings are reversed, direction of rotation of
armature will be unchanged.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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DC MACHINES
As the mechanical load on the armature i.e. rotor
shaft represented by load torque TL is
increased, more and more electro-magnetic torque
will be developed by the armature to balance the
mechanical torque requirements for which the
armature will draw more current from the supply
mains.
APPLICATION CONCEPT OF ALIGNMENT OF TWO MAGNETIC
FIELDS
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MAGNETIC FIELD
A
B
?
A
A
Q
P
B
LOAD
0o
21
MAGNETIC FIELD
A
B
?
A
Q
P
_

B
e
LOAD
30o
?t
22
MAGNETIC FIELD
A
B
?
A
Q
P

_
B
e
LOAD
60o
?t
23
MAGNETIC FIELD
A
B
?
A
Q
B
P

_
e
LOAD
90o
?t
24
MAGNETIC FIELD
B
A
?
A
B
Q
P

_
A
e
LOAD
120o
?t
25
MAGNETIC FIELD
B
A
?
B
A
Q
P

_
A
e
LOAD
150o
?t
26
MAGNETIC FIELD
B
A
?
B
A
Q
P

A
e
LOAD
180o
?t
27
MAGNETIC FIELD
B
A
?
B
Q
P

_
A
e
LOAD
210o
?t
28
MAGNETIC FIELD
B
A
?
B
Q
P

_
A
e
LOAD
240o
?t
29
MAGNETIC FIELD
B
A
?
B
Q
A
P

_
e
LOAD
270o
?t
30
MAGNETIC FIELD
A
B
?
A
A
Q
P

_
B
e
LOAD
300o
?t
31
MAGNETIC FIELD
A
B
?
A
A
Q
P

_
B
e
LOAD
330o
?t
32
MAGNETIC FIELD
A
B
?
A
A
Q
P
B
e
LOAD
360o
?t
33
DC MACHINES
INTODUCTION
A DC machine is an electro-mechanical energy
conversion device. It can convert Mechanical
power into Electrical Power. When output
electrical power is DC , it is called DC
Generator. When it converts DC electrical power
into mechanical power , it is known as DC Motor.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
1. BODY OR MAGNETIC FRAME OR YOKE
2. POLE CORE AND POLE SHOES
3. FIELD or EXCITING COILS
4. ARMATURE CORE
5. ARMATURE WINDING
6. COMMUTATOR
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
7. BRUSHES
8. END HOUSINGS
9. BEARINGS
10. SHAFT
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
Brush
Bearing
Body / Yoke
Pulley
End Housing
Shaft
Armature
Commutator
Field Core
Brush holder
Field Winding
Click here to see photograph
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
YOKE
ARMATURE

SHAFT
FIELD POLE COIL
BRUSH
-
COMMUTATOR
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
1. MAGNETIC FRAME or YOKE
The outer cylindrical frame to which main poles
and inter poles are fixed and by means of the
machine is fixed to the foundation is called
YOKE.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
1. MAGNETIC FRAME or YOKE
It serves two purposes a) It provides
mechanical protection to the inner parts of the
machines.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
1. MAGNETIC FRAME or YOKE
b) It provides a low reluctance path for the
magnetic flux. The yoke is made of cast iron for
smaller
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
1. MAGNETIC FRAME or YOKE
machines and cast steel or fabricated rolled
steel for larger machines.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
2. POLE CORE AND POLE SHOES
The pole core and pole shoes are fixed to the
yoke by bolts. They serves the following purpose
a) They support the field or exciting coils.
POLE CORE
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
2. POLE CORE AND POLE SHOES
b) They distribute the magnetic flux on the
armature periphery more uniformly.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
2. POLE CORE AND POLE SHOES
c) The pole shoes have larger X- section, so,
the reluctance of the magnetic path is reduced.
The pole core
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
2. POLE CORE AND POLE SHOES
and pole shoes are made of laminated steel
assembled by riveting together under hydraulic
pressure.
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
3. FIELD or EXCITING COILS
Field coils or exciting coils are used to
magnetise the pole core. Enameled copper wire is
used for the construction of these coils.When
direct
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
3. FIELD or EXCITING COILS
current is passed through these coils/ winding,
it sets up the magnetic field which magnetise the
pole core to the reqd. flux.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
4. ARMATURE CORE
Armature is a rotating part of the DC machine,
reversal of flux takes place, so hysteresis
losses are produced. To minimise this loss,
silicon steel is used for the construction.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
4. ARMATURE CORE
The rotating armature cuts the main magnetic
field , therefore an e.m.f is induced in the
armature core.This e.m.f circulates eddy currents
in the core which results in eddy current loss in
it.
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
50
DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
4. ARMATURE CORE
The armature core is laminated to reduce the eddy
current loss. Armature core serves the following
purposes a) It houses the conductors in the
slots. b) It provides an easy path for magnetic
flux
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
The no. of conductors in form of coils placed in
the slots of the armature and suitably inter
connected are called winding .
ARMATURE WINDING
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
This is the armature winding where conversion of
power takes place i.e. in case of generator ,
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
mechanical power is converted into electrical
power and in case of a motor, electrical
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
power is converted into mechanical power.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
Depending upon the types of inter connection. of
coils , the winding can be classified into two
types i) Lap Winding The conductors/coils are
connected in such a way that no of parallel paths
are equal to no. of poles.
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
If machine has P no. of poles and Z no. of
conductors, then there will be P no. of
parallel paths.And each path will have Z/P no
of conductors in series. Also the no. of brushes
are equal to no. of parallel paths.
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
Out of which half of the brushes will be positive
and remaining will be negative. ii) Wave
Winding The conductors are so connected that
they are divided into two parallel paths only ,
irrespective of the no. of poles. If machines has
Z no. of
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
5. ARMATURE WINDING
conductors, there will be only two parallel paths
and each will be having Z/2 no. of conductors
connected in series with only two brushes.
Click here to study detailed contents of winding
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
It is the most important part of a DC machine and
serves the following purpose - i) It connects
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
the rotating armature conductors to the
stationary external circuit through the brushes.

MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
ii) It converts altering current induced in the
armature conductors into unidirectional ..
COMMUTATOR
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
current in the external load circuit in
generating action and it converts alternating
torque into unidirectional
COMMUTATOR
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
COPPER SEGMENT RISER
MICA INSULATION
END RING
ADJUSTING NUT
METAL SLEEVE
SHAFT
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
torque produced in the armature in motoring
action. The commutator is of cylindrical shape
and is made of wedge shaped hard drawn copper
segments.The segments are insulated from each .
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
6. COMMUTATOR
other by a thin sheet of mica.The segments are
held together by means of two V-shaped rings that
fit into the V-grooves cut into the segments.
Each armature coil is connected to the commutator
segment through riser.
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
7. BRUSHES
Brushes are made of high grade carbon.They form
the connecting link between armature winding and
the external circuit. The brushes are held in
particular position around the commutator by
brush holders.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
8. END HOUSINGS
They are attached to the ends of main frame and
support bearing . The front housing supports ..
END HOUSING
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
8. END HOUSINGS
the bearing and the brush assembly whereas rear
housing supports the bearing only.
END HOUSING
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
9. BEARINGS
The function of the bearing is to reduce friction
between the rotating and stationary parts of the
machines.These are fitted in the end housings.
Generally, high carbon steel is used for the
construction of the bearings.
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
10. SHAFT
The function of shaft is to transfer mechanical
power to the machine or from the machine .
SHAFT
MAIN CONSTRUCTIONAL FEATURES
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
10. SHAFT
Shaft is made of mild steel with maximum breaking
strength. All the rotating parts like
SHAFT
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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DC MACHINES
MAIN CONSTRUCTIONAL FEATURES
10. SHAFT
armature core, commutator, cooling fan etc. are
keyed to the shaft.
SHAFT
See Also
MAIN CONSTRUCTIONAL FEATURES
LECTURE 7 OF 40
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TYPES OF EXCITATIONS ( DC MOTORS )
Depending upon the type if excitation to the
field winding , The dc machine can be classified
into three categories viz. Machines with
permanent field,
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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TYPES OF EXCITATIONS ( DC MOTORS )
separately excited and self excited type dc
machines. Dc motors with permanent magnetic
field, are manufactured for small rating
applications such as toys, cassette tape
recorders etc.large rating dc motors
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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TYPES OF EXCITATIONS ( DC MOTORS )
are constructed with electro-magnetic field i.e
field winding is placed on the field core and
this winding is supplied with dc current called
excitation. Depending upon the type of
connections to the field winding for .
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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TYPES OF EXCITATIONS ( DC MOTORS )
excitation , the dc motors can be classified into
two categories 1) Separately excited dc
motors 2) Self excited dc motors.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SEPARATELY EXCITED DC MOTORS

Ia

A
Rf
F
FF
E
V
M
If
Supply
Ra
_
AA
VDC
_

_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SEPARATELY EXCITED DC MOTORS

• The field winding is excited from a supply which
  is not connected to the armature winding. It may
  be noted that current flowing through the field
  winding is independent of load and is equal to V
  / Rf , where Rf is the.

DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SEPARATELY EXCITED DC MOTORS
field circuit resistance. The flux produced is
proportional to the field current i.e. Ø ? If
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC SHUNT MOTORS )

Ia
IL
If
F
A
V
E
M
SUPPLY
Ra
FF
AA
_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC SHUNT MOTORS )
In this type of excitation , armature and field
windings are connected across a constant source
of supply. The field current If is drawn from the
same source as that of armature current. As shown
in fig.
See Fig.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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SELF EXCITED DC MOTORS ( DC SERIES MOTORS )
Y
YY

Ia

IL
ISE
A
V
E
M
SUPPLY
Ra
_
AA
_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC SERIES MOTORS )
The field winding is connected in series with the
armature so that If Ia IL . Therefore field
winding is made up of thick winding wire of less
no. of turns as compared to that of shunt field
winding so that armature current can ...
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC SERIES MOTORS )
flow through it without overheating. In case of
dc series machine , Ø ? If ? Ia .. The
relationship between induced e.m.f. and terminal
voltage is as follows ..
See Fig.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC SERIES MOTORS )
V E Ia Ra Ia Rse
or
E V - Ia ( Ra Rse )
Ia Ise IL
and
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
ISh
Y
YY

IL
Ia
ISE
A
Z
Rsh
SUPPLY
E
V
M
Ra
ZZ
AA
_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
There are two field windings , namely a shunt
field winding and a series field winding. The
shunt field winding is connected in parallel with
the armature and series field winding is
connected in series with the combination .
See Fig.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
Series field winding will carry a large armature
current Ia or IL and therefore it is made of wire
of large cross section and has a few turns only.
The resistance of series field winding is very
small.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
The shunt field winding is made up of wires of
small cross section and has high resistance.
Since the resistance of shunt field winding is
high , the current flowing through it is very
small as compared to that of series field winding
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
or armature current Ia . The main magnetic field
flux is produced by the shunt field current /
winding but it is modified by the field of series
winding. A compound machine therefore combines
the best features of dc shunt machines and dc
series machines.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
Depending up on the connections of shunt field
winding in the combination of armature and series
field winding, dc compound generators can be
named as i) Short shunt compound generators. ii)
Long shunt compound generators.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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SHORT SHUNT TYPE ( DC COMPOUND MOTORS )
ISh
Y
YY

IL
Ia
ISE
A
Z
Rsh
SUPPLY
E
V
M
Ra
ZZ
AA
_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SHORT SHUNT TYPE ( DC COMPOUND MOTORS )
i) SHORT SHUNT DC COMPOUND MOTORS
In this case the shunt field winding is connected
across the armature winding only as shown in the
fig of slide no.
Ise IL Ia Ish
V E Ia Ra Ise Rse E Ia Ra ( Ia
Ish ) Rse
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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LONG SHUNT TYPE ( DC COMPOUND MOTORS )
Y
YY

IL
Ia
Z
ISE
A
Rsh
SUPPLY
E
V
M
ISh
Ra
AA
ZZ
_
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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LONG SHUNT TYPE ( DC COMPOUND MOTORS )
ii) LONG SHUNT DC COMPOUND MOTORS
In this case the shunt field winding is connected
across the combination of armature and series
field winding as shown in the fig.
Ise Ia and IL Ia Ish
V E Ia Ra Ise Rse Ish Rsh
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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SELF EXCITED DC MOTORS ( DC COMPOUND MOTORS )
Depending upon the direction of flow of current
through series field, we can classify dc compound
motors into two categories namely I)
Cumulative compound dc motors II) differential
compound dc motors
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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CUMULATIVE TYPE ( DC COMPOUND MOTORS )
ISh
Y
YY

IL
Ia
ISE
A
Z
Rsh
SUPPLY
E
V
M
Ra
ZZ
AA
_
Ø Øsh Øse
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
LECTURE 9 OF 40
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CUMULATIVE TYPE ( DC COMPOUND MOTORS )
The direction of current in the series field
winding is such that magnetic field produced by
it is in the direction to that of shunt field.
Total magnitude of the field is the sum of shunt
field and series field so that Ø Øsh Øse. .
See Fig.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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DIFFERENTIAL TYPE ( DC COMPOUND MOTORS )
ISh

Y
YY
IL
Ia
A
Z
ISE
Rsh
SUPPLY
E
V
M
Ra
ZZ
AA
_
Ø Øsh - Øse
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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DIFFERENTIAL TYPE ( DC COMPOUND MOTORS )
The direction of current in the series field
winding is such that magnetic field produced by
it is in the opposite direction to that of shunt
field. Total magnitude of the field is the
difference of shunt field and series field so
that Ø Øsh - Øse.
See Fig.
DIFFERENT TYPES OF EXCITATIONS ( DC MOTORS )
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FACTORS DETERMINING THE SPEED OF DC MOTOR
The expression for back e.m.f. developed in the
armature of a dc motor is given as follows
P Ø Z N
..(i)
E
60 A
..(ii)
E
V - Ia Ra
FACTORS DETERMINING THE SPEED OF DC MOTOR
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FACTORS DETERMINING THE SPEED OF DC MOTOR
Comparing expressions (i) and (ii)
P Ø Z N

V - Ia Ra
60 A
K Ø N

V - Ia Ra
OR
V - Ia Ra
N

K Ø
FACTORS DETERMINING THE SPEED OF DC MOTOR
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FACTORS DETERMINING THE SPEED OF DC MOTOR
Where K is the constant of proportionality and
equal to PZ / 60 A
Now in the above expression for speed, the speed
can be varied by varying the applied voltage V
, field flux Ø and resistance of the armature .
FACTORS DETERMINING THE SPEED OF DC MOTOR
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FACTORS DETERMINING THE SPEED OF DC MOTOR
It is clear that speed is directly proportional
to the supply voltage V. So the speed increases
with increase in voltage V and vice versa. The
speed is inversely proportional to the field flux
Ø . So speed decreases as the Flux Ø increases
and vice versa.
FACTORS DETERMINING THE SPEED OF DC MOTOR
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CHARACTERISTICS OF DC MOTORS
The important characteristics of dc motors are
1) Speed - armature current ( Load )
characteristics 2) Torque - armature current (
Load ) characteristics 3) Speed -
Torque characteristics
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC MOTORS
It is very much important to know the
characteristics mentioned above for different
types of dc motors because it enables the
selection of a specific type of dc motor for
specific purpose.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS

Ia
IL
If
F
A
V
E
M
SUPPLY
Ra
FF
AA
_
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
N
FULL LOAD
0
Ia
( Amps)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
1. Speed - Armature current (Load )
characteristics
For a dc motor , we know that
V - Ia Ra
N
K Ø
A dc shunt motor is connected across the mains
having supply voltage V .
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
Speed - Armature current (Load ) characteristics
This supply voltage is assumed to be constant.The
field winding is connected across the armature as
shown in Fig. The magnetic flux Ø produced by
field current If will be constant as V remains
constant.
See Fig.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
1. Speed - Armature current (Load )
characteristics
But in actual practice, the air gap flux is
slightly reduced due to the effect of armature
reaction. From the expression for the speed
mentioned earlier, it is evident that as the
armature current Ia ...
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
1. Speed - Armature current (Load )
characteristics
increases , speed will decrease by a small amount
due to an increase in Ia Ra drop is very small as
compared to V . The speed verses armature
current characteristics is shown in Fig.
See Fig.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
1. Speed - Armature current (Load )
characteristics
The shunt motor being thus more or less a
constant speed motor , can be used in the
applications such as driving of line shafts,
lathes conveyors etc.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
2. Torque - Armature current (Load )
characteristics
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
2. Torque - Armature current (Load )
characteristics
The equation for torque can be written as follows

T kt Ø Ia
If flux Ø is taken as constant, the torque T
becomes directly proportional to armature current
(Load current) Ia . It is a straight line passing
through the origin.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
3. Speed - Torque characteristics
N
0
T
( N-m)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SHUNT MOTORS
3. Speed - Torque characteristics
The relation between T and Ia and N and Ia are
as under
T kt Ø Ia
V - Ia Ra
N
K Ø
And The relationship between speed and torque can
be drawn as shown in Fig .
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
Y
YY

Ia

IL
ISE
A
V
E
M
SUPPLY
Ra
_
AA
_
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
N
0
Ia
( Amps)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
V - Ia Ra
From the expression
N
K Ø
It is seen that the speed N is inversely
proportional to flux Ø For a dc series motor
,magnetic flux Ø is proportional to Ia.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
Thus , if V is constant, N is inversely
proportional to Ia. The N verses Ia
characteristics is therefore a rectangular
hyperbola as shown in Fig . It is seen from the
characteristics that .
See Fig.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
the speed decreases as the load on the motor
increases. At a very low load , the speed is
dangerously high . Thus if a dc series motor is
allowed to run on very light load or at No- Load
, its speed will become much higher than its ..
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
normal speed which may cause damage to the motor.
For this reason , dc series motors are never
started on No- Load and are not used in the
applications where there is a chance of Load
being completely removed , when the motor ...
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
remains connected to the supply. The load on the
dc series motor is connected through the gears
and not through the belt pulley arrangement.This
is because, in case of failure of belt , the load
will be removed from the motor and thereby the
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Speed - Load characteristics
motor will attain a dangerously high speed . In
case of load connected through the gears, however
in the event of an accidental release of load,
gears will provide some load on account of the
frictional resistance of the gear teeth.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Load characteristics
SATURATION OF SERIES FIELD CORE
T
0
Ia
( Amps)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Load characteristics
The equation for the torque for dc motor is
given by T kt Ø Ia The magnetic flux for a dc
series motor is proportional to armature current
Ia. Thus the torque T kt Ia Ia. Or T ? Ia2
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Load characteristics
The relationship between torque and armature
current , is therefore of the form of a parabola
. With increase in Ia , the field flux increases
linearly but due to saturation of the core,
beyond a certain magnitude of Ia the increase in
flux is
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Load characteristics
negligible.. Thus T is proportional to the
square of Ia up to the saturation point beyond
which T varies linearly with Ia. From the
torque load characteristics , it can be observed
that a dc series motor ..
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Load characteristics
started on-load , develops a very high starting
torque. Hence dc series motors are used in
applications where high starting torque is
required such as in electric trains , hoists,
trolleys etc.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Speed characteristics
N
0
T
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Speed characteristics
From the characteristics shown in slide no. , it
can be seen that for low speeds , the torque is
high and for high speeds the torque is very
small. This is why dc series motor is widely
used in the ..
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC SERIES MOTORS
1. Torque - Speed characteristics
applications where motor is to be started on bulk
loads such as electric loco- motive.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
ISh
Y
YY

IL
Ia
ISE
A
Z
Rsh
SUPPLY
E
V
M
Ra
ZZ
AA
_
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
1. Speed - Load characteristics
DIFFERENTIAL COMPOUND
N
SHUNT
CUMULATIVE COMPOUND
0
Ia
( Amps)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
1. Speed - Load characteristics
In cumulative compound motors , series field
winding is connected in such a way that magnetic
flux produced by it helps the flux produced by
shunt field winding. Series field is directly
proportional to the load current , .. . .
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
1. Speed - Load characteristics
therefore total flux increases with increase in
load current / armature current due to the series
field in addition to the voltage drop in the
armature winding.The speed of dc motor is
inversely proportional to the . .. . ..
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
1. Speed - Load characteristics
total main flux Ø . Therefore speed drops more
sharply as compared to dc shunt motor.Refer Fig.
See Fig.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
2. Torque - Load characteristics
T
CUMULATIVE COMPOUND
SHUNT
DIFFERENTIAL COMPOUND
0
Ia
( Amps)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
2. Torque - Load characteristics
The torque developed by a cumulative compound
motor increases with sudden increase in load and
at no-load , it has a definite speed. Cumulative
compound motors are therefore, suitable where
there is sudden application . . . . . . .
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
2. Torque - Load characteristics
of heavy loads like sheers, punches, rolling
mills etc. The speed of differential compound
motors remains more or less constant. With
increase in load but its torque decreases with
load. Since the dc shunt motor develops a good
torque and
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
2. Torque - Load characteristics
its speed does not vary appreciably with increase
in load, differential compound motors are not
preferred over dc shunt motors and hence are
rarely used.
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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CHARACTERISTICS OF DC COMPOUND MOTORS
3. Speed - Torque characteristics
DIFFERENTIAL COMPOUND
N
CUMULATIVE COMPOUND
0
T
(N-m)
PERFORMANCE AND CHARACTERISTICS OF DC MOTORS
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APPLICATIONS OF DC MOTORS
(a) DC SHUNT MOTORS
(i) Shunt motors are used in situations, such as
driving a line shafting etc. where the speed as
to be maintained approximately constant between
no-load and full-load.
APPLICATION OF DC MACHINES
145
APPLICATIONS OF DC MOTORS
(a) DC SHUNT MOTORS
(ii) In situations where variable load is to be
driven at different speeds but at each load, the
speed is to be kept constant. Such as driving a
lathe.
APPLICATION OF DC MACHINES
146
APPLICATIONS OF DC MOTORS
(b) DC SERIES MOTORS
DC Series Motors are used in applications such as
driving hoists, cranes, trains, etc., as in these
cases a large starting torque is required. They
are also used where the motor can be permanently
coupled to the load, such as
APPLICATION OF DC MACHINES
147
APPLICATIONS OF DC MOTORS
(b) DC SERIES MOTORS
Fans , whose torque increases with speed. Where
constancy in speed is not essential, the decrease
of speed with increase of load has the
advantage that the power absorbed by the motor
does not increase as rapidly as the torque .
APPLICATION OF DC MACHINES
148
APPLICATIONS OF DC MOTORS
(b) DC SERIES MOTORS
Series motors acquire very high speed at no-load
or at very light load . That is why they should
not be used for a belt drive where there is a
possibility of the load decreasing to very small
value.
APPLICATION OF DC MACHINES
149
APPLICATIONS OF DC MOTORS
(c) DC COMPOUND MOTORS
DC Compound Motors are used in application where
large starting torque are required but where the
load may fall to such a small value that a series
motor would reach a dangerously high speed.
APPLICATION OF DC MACHINES
150
APPLICATIONS OF DC MOTORS
(c) DC COMPOUND MOTORS
Where the supply voltage may fluctuate , for
instance on a traction system, the series winding
reduces the fluctuation of armature current
partly by its inductance and partly by its
influence on the value of
APPLICATION OF DC MACHINES
151
APPLICATIONS OF DC MOTORS
(c) DC COMPOUND MOTORS
flux and therefore on that of the induced
e.m.f. When the load is of a fluctuating nature ,
e.g. for driving stamping processes, etc. the
shunt excitation prevents the speed
APPLICATION OF DC MACHINES
152
APPLICATIONS OF DC MOTORS
(c) DC COMPOUND MOTORS
Becoming excessive on light load, and the
decrease of speed with increase of load enables
the flywheel, usually fitted to such a machine,
to assist the motor in in dealing with the peak
load by giving
APPLICATION OF DC MACHINES
153
APPLICATIONS OF DC MOTORS
(c) DC COMPOUND MOTORS
up some of its kinetic energy.
THANKS
APPLICATION OF DC MACHINES
154
THANKS