1.
Speed control of dc motor using
chopper
Presented by: Under the guidance of:
Ajeeta Srivastava (1473720005) Assi. Prof. Nikhil Chowdhary
Akansha (1473720006)
DEPARTMENT OF ELECTRICAL ENGINEERING
RAJKIYA ENGINEERING COLLEGE
AMBEDKAR NAGAR-224122(U.P.)

2.
Abstract
The speed of a d.c. motor is given by relationship
N= ( V- Ia Ra)/kΦ
Speed of dc motor can be varied by following methods
 Armature voltage control (for below base speed)
 Field flux control (for above base speed)
 Armature resistance control
Here, we are using armature voltage control method for
speed control. In this method, the voltage applied to
armature circuit, V is varied using DC-DC converter, a
power electronics device which converts fixed dc input
voltage to a variable dc output voltage.

3.
Introduction
 Chopper are static power electronics device which
converts fixed dc input voltage to a variable dc
output voltage. It can be step-up or step-down.
 Separately excited dc motor has field winding and
armature winding with separate supply voltage.
 Field winding supplies field flux to armature.
 When dc voltage is supplied to motor, current is fed
to the armature winding through brushes and
commutator .

4.
Choppers
Choppers are DC-DC converters that converts fixed DC input voltage to
a variable DC output voltage.
These are widely used in regulated switching power supplies and dc
motor drives application.

5.
Types of Choppers
There are two types of choppers:
 Step-up chopper: In this the output voltage is more
than input voltage.
 Step-down chopper: In this the output voltage is less
than input voltage.

6.
Principle of Chopper operation
 There are basically two time periods in chopper
operation, one is the “on” time denoted as TON and
other is the “off” time denoted as TOFF.
 During TON we get the constant source voltage VS
across the load and during TOFF we get zero voltage
across the load.
 In this way we obtain a chopped dc voltage at the load
terminals.

7.
WORKING
Average Voltage, Vo= (Ton/ (Ton+Toff))*Vs
= (Ton/T)*Vs
=αVs

8.
Working Of Separately Excited DC
Motor
 Separately excited dc motor has field and armature
winding with separate supply voltage.
 Field winding supplies field flux to armature.
 When dc voltage is applied to motor , current is fed to
armature winding through brushes and commutator.
 Since rotor is placed in magnetic field and it is carrying
current also. So motor will develop the back e.m.f. and
torque to balance load torque at particular speed.

9.
Block Diagram
INPUT DC
CHOPPER
OUTPUT
(variable
dc
voltage)
Separatel
y excited
dc motor
DISPLAY
(current
,voltage ,
speed)
PI Controller
Reference
speed

10.
Application of chopper in DC
Motor
1) For regenerative braking of DC motor
2) Power control or motoring control
3) Choppers are used in electric cars, airplanes and
spaceships, where onboard-regulated DC power
supplies are required.

11.
Simulation Result
The simulink model of speed control of DC motor is
shown in figure 4. It consists of speed controller ,
current controller, filter , chopper and a motor . Now the
simulation of model is done and analyzed in MATLAB
(Simulink) under varying speed and torque condition.
The result from the simulation of the motor model in
SIMULINK is shown in figure 5(a),5(b),5(c),6(a),6(b)
and 6(c).

12.
Fig 4. Chopper fed separately excited dc motor

13.
Fig 5 (a) output voltage (b) output current (c) speed of dc motor for step
torque

14.
Fig 6 (a) output voltage (b) output current (c) speed of dc motor
for constant torque

15.
Conclusion
The speed of a DC motor has been successfully
controlled by using chopper as converter and
proportional-integral type speed and current controller
based on closed loop model of dc motor. The simulation
is done in MATLAB under varying load condition and
varying reference speed condition .We can also
implement it in hardware to observe actual feasibility.

16.
References
Websites:
www.wikipedia.com/chopper
www.electrical4u.com/speed-control-of-dc-motor
Books:
(1)Dr. P.S. Bimbhra “Power Electronics” ,Khanna Publishers.
(2) Dr. P.S. Bimbhra “Electrical Machinery” ,Khanna
Publishers.
(3)Ashfaq Hussain “Electric Machine”,Dhanpat Rai & Co.
(4)Muhammad H. Rashid “Power Electronics” Pearson

17.
THANK YOU….