DC Motor and its control using Pulse Width Modulation.

1. --Rishabh Shukla
DC MOTOR & ITS CONTROL

2. CONTENTS:-
1. Parts of Motor.
2. Basic of Operation
3. Types of AC Motor
4. Types of DC Motor
5. Design
Parameters
6. Electrical Analysis
7. Switching Circuit
8. Speed Control
9. Torque Control
10. Motion Profile

3. PARTS OF DC
MOTOR:-
1. Yoke 2. Pole
3. Field
Winding
4. Armature
Winding
5. Commutator &

4. 1. Converts direct
current(electrical energy) into
mechanical energy.
2. Extensively used in Industry &
vital for Engineers.
*TWO EQUAL AND OPP FORCE CONSTITUTE
TORQUE*
BASIC OPERATION:-

5. Parameters Synchronous Induction
Slip No ~Interlocking Yes~ Phase difference
Excitation Double
(Armature+Field)
Single
Application Timer/ Tape Recorders 90% of Industrial
motors
Principle Interaction of B Field of
Stator & Rotor.
I flows in stator—
induces B Field.
Types of AC Motor :-

6. Parameters Brush Brushless
Commutation
Mechanism
Mechanical using
Brush
Via Electronic Switching
Circuit
Mechanical Friction Yes No
Arcing/ Sparks Yes No
Max Speed Limited by Brush Greater
Thermal Characteristics Difficult
(Electromagnet is on
Rotor)
Improved thermal
characteristics.
Motion Precision Less More
System Weight More Less
Types of DC Motor On the basis of Commutation:-
*THE ACT OF CHANGING DIRECTION OF CURRENT IS CALLED
COMMUTATION*

7. *DESIGN PARAMETERS:-
Parameters Definition
1 Stall Torque Is the torque produced by the motor when at standstill.
2 Nominal Torque Is the torque generated for operation at nominal voltage
and nominal current at temp of 25 degree C
3 Speed/Torque
Gradient
Indicator of Motor Performance. Smaller the value more
powerful the motor. It is quotient of no load speed and ideal
stall torque.
4 Mechanical Time
const
Time required for rotor to accelerate form standstill to
63% of its no load speed
5 Nominal Voltage Is the applied voltage between two powered phases in
bolck commutation mode
6 Thermal time
constant
Typical reaction time for a temperature change of winding
and motor

8. Electrical Analysis of a DC Motor
Where, P = no of poles
φ = flux per pole
Z= No. of conductors
A = No. of parallel paths
and N is the speed of the DC Motor.
Eb is proportional to speed ‘N’.
So when the speed of the motor is reduced by the application of
load, Eb decreases. means E − Eb increases.
Due to this increased voltage difference,
armature current will increase and
therefore torque and hence speed
increases. Thus a DC Motor is capable of
maintaining the same speed under variable
load.
As a result we need to use a starter for
starting a DC Motor.
NEED OF STARTERS:-

9. 1. Based on the position of the motor
(identified using feedback sensor)
two of the three electrical windings
are energized at a time.
2. External circuit should be able to
meet the current requirement of
motor.
Switching Action cause the
Stator’s B to rotate. ---
Bidirectional Currents are
produced.
A total of six switches are
needed for one BLDC motor.
*SWITCHING CIRCUIT:-

10. The Motor Speed depends on the amplitude of applied voltage, which is
adjusted using Pulse Width Modulation (PWM)
By controlling the duty cycle of the PWM signal . The amplitude of the
applied voltage can be controlled, which in turn will control the speed of
the motor.
*SPEED CONTROL:-

11. * MAXIMUM PERMISSIBLE SPEED :-
•Max Speed is limited by the commutation system
•At very high speed, commutators and brush wear more
rapidly, causing reduce in life of motor.
•At high speed arcing is more pronounced.
Mn- Rated Torque.
Tw- Thermal time constant

12. Where, P is no of poles,
φ is flux per pole,
Z is no. of conductors,
A is no. of parallel paths,
and N is the speed of the D.C.
motor.
*TORQUE CONTROL:-

13. 1. TRIANGULAR:-
2. TRAPEZOIDAL:-
More rapid the change
in acceleration, the more
powerful the
vibrations will be
*MOTION CONTROL:-
JERK= CHANGE IN
ACCLERATION
TIME

14. 3. S -Type:-
Induced vibration for S
curve and trapezoidal
mode.
4. VIBRATION IN
SYSTEM:-
*VIBRATION ANALYSIS:-

15. *CHALLENGES:-
•TO KNOW THE KEY REQUIREMENTS OF FORCES/
TORQUES and VELOCITIES (SPEED OF ROTATION)??
•HOW LONG THEY MUST BE APPLIED??
•DESIGN A DRIVING MECHANISM BY CALCULATING THE
MOMENT OF INERTIA OF ROTATING LOAD.
•GEARHEAD DESING
•CHOOSE BETWEEN AVALIABLE MOTORS.
•SENSOR CONTOLLER
•COST CONSIDERATION

16. *REFERNECE:-
1. Maxon Motros
2. Electrical For you
3. Wikipedia