This document discusses the design and implementation of a speed control system for separately excited DC motors using microcontrollers and pulse width modulation (PWM) techniques. It explains different methods for speed control, the connection between armature voltage and motor speed, and compares simulation results with practical results. The advantages of using microcontrollers include ease of control, low cost, high accuracy, and increased reliability.

1. BY : Mohammed Alabdali – Abdullah Sha’abi – Ismael Hazazi – Mohammed Alhashim – Saud Athwani
Supervisor : prof. Mohammed Mustafa
DC motors are used in many applications like electric railway
traction and many more industrial fields such as rolling mills, paper
industries etc. because they can provide a high starting toque.
They require controlling of speed to perform their tasks.
In DC motor we can control over a wide speed range, both below
and above the rated speed can be very easily achieved. The
methods of speed control are simpler less expensive than
Those of alternating current motors.
There are Different techniques available for speed control of DC
motors
In this project the combined armature and field speed control of
separately excited DC motor using micro- controller has been
designed and implement using pulse width modulation (PWM)
technique. The pulse width modulation can be achieved in several
ways. In the present project, the PWM generation is done using
micro- controller.
between armature voltage and speed
At speed 1000 rpm At speed 2000 rpm
Armature voltage
31.30 V
Motor Speed
253 rpm
Armature voltage and current
waveform at 13.17% duty cycle
Armature voltage
160.4 V
Motor speed
1654 rpm
Armature voltage and current
waveform at 69.73% duty cycle
-150
350
850
1350
1850
2350
-20 30 80 130 180 230
Speedrpm
Voltage V
Armature Voltage vs Motor speed
-150
350
850
1350
1850
2350
0 10 20 30 40 50 60 70 80 90 100
Speedrpm
Duty Cycle %
Motor Speed vs Duty Cycle
between duty cycle and speed
Three phase rectifier output wave formoutput voltage of three phase AC supply
A simulation model was proposed for the proposed system and
experiments were performed at different speeds The simulation
results were compared with the practical results and it was
found that the simulation results matched with the practical
results
Varying the armature voltage and keeping field constant ( motor speed
varies from 0 to rated speed )
Varying field voltage and keeping armature voltage constant ( motor
speed range from rated speed to above rated speed Buck
converter gives high
-Using efficiency ,smooth control speed range from 0to twice rated
speed .Feature many desirable
-IGBTs properties including a MOSFET input
gate ,high switching speed,low
conduction voltage drop ,high current carrying capability, and a high
degree of robustness.
-Using microcontroller for
Speed control gives the following
advantages:
Easy control.
o Low cost.
o High accuracy.
o Reduces the control hardware.
o Increases the reliability and brings in flexibility to the control.