Download DC shunt motor DC series motor

Speed control methods are applied to dc shunt, dc
series & dc compound motors.
Speed control methods of
D.C. series motor
D.C. shunt motor
1. Flux Control
2. Rheostatic Control
Method
3. Voltage Control
Method
a) Multiple voltage
control
b) Ward-Leonard System
1. Flux Control Method
a) Field Diverters
b) Armature Diverter
c) Trapped Field control
field
d)Paralleling Field Coils
2. Variable Resistance
Method
1) Speed Control of shunt motors
Advantages of flux control method :
Drawbacks :
• Speed below the normal can not be obtained.
• Higher speeds can only be obtained at reduced torque due
to very weak field.
Use : This method is used when speeds below the no-load
speed are required.
3) Voltage Control Method
a) Multiple Voltage Control
• The shunt field of the motor is permanently to a fixed
exciting voltage, and the armature is supplied with
different voltages.
• So the voltage across armature speed is approximately
proportional to the voltage across the armature.
b) Ward-Leonard System
• This Ward-Leonard system is used when very sensitive
speed control of the motor is required.
• The arrangement of this system is as required in the figure
shown below.
(2) Uniform acceleration can be obtained.
(3) Good speed regulation
Disadvantages :
(1) This arrangement is costly due to two extra machines.
(2) Overall efficiency of the system is low.
1) Flux Control Method : Variation in the flux of a series
motor can be brought about in any one of the following
ways :
(a) Field Divertors :
 A Rheostat is connected
parallel to the series field
as shown in fig(a).
 The series winding are shunted by a variable resistance
known as field divertor.
 Any desired amount of current can be passed through
the divertor by adjusting its resistance.
 Hence the flux can be decreased and consequently, the
speed of motor increased.
(b)Armature Divertor
Figure(b)
(c) Trapped field Control Field
 The method is often used in electric
traction and is shown in fig.
 The number of series field turns in
the circuit can be changed at will as
shown. With full field, the motor
runs at its minimum speed which can
be raised in steps by cutting out some
of the series turns.
(d) Paralleling Field coils
• This method is usually employed in the case of fan
motors.
• By regrouping the field coils as shown in figure ,
several fixed speeds can be obtained.
(2) Variable Resistance in Series with Motor
By increasing the resistance in
series with the armature the
voltage applied across the
armature terminals can be
decreased.
With reduced voltage across the armature, the speed is
reduced. However, it will be noted that
since full motor current passes through this
resistance, there is a considerable loss of power in it.
Name
1)
2)
3)
4)
Ankita M. Patel
Divya M. Patel
Mukesh Rana
Kinjal D. Tandel
Enrolment No.
140190109027
140190109032
140190109052
140190109059