DC motors generate torque directly from DC power using internal commutation and stationary magnets. Brushless DC motors use rotating magnets and stationary coils. AC motors have a stationary stator with coils powered by AC current to generate a rotating magnetic field, and a rotor given torque. DC motors offer excellent speed control but require more maintenance due to brushes. AC motors are cheaper, more reliable with no brushes, allow for speed variation, and have high power factors, making them suitable for most industrial applications powered by AC sources. Both motor types have advantages dependent on the application.

2. Introduction
DC Motor
 DC motor is an electric motor that runs on direct
current (DC) electricity.
 Two types of DC motor - brush and brushless DC
Motor.
 Brushed DC electric motor generates torque
directly from DC power supplied to the motor by
using internal commutation, stationary magnets
(permanent or electromagnets), and rotating
electrical magnets.
 Brushless DC motors use a rotating permanent
magnet or soft magnetic core in the rotor, and
stationary electrical magnets on the motor
housing.

3. Operation of DC Motor

4. Operation of DC Motor
1. When the coil is powered, a magnetic field is generated
around the armature. The left side of the armature is
pushed away from the left magnet and drawn toward the
right, causing rotation.
2. The armature continues to rotate.
3. When the armature becomes horizontally aligned, the
commutator reverses the direction of current through the
coil, reversing the magnetic field.
4. The process then repeats.

5. Advantages of DC Motor
Overall advantages that will be discussed are;
1. Provide excellent speed control for acceleration and
deceleration.
2. Easy to understand design
3. Simple, cheap drive design

6.  Provide excellent speed control
- power supply of a DC motor connects directly to the field
of the motor allows for precise voltage control, which is
necessary with speed and torque control applications. (DC
shunt motor)
- The higher the armature voltage, the faster the rotation.
This relationship is linear to the motor's maximum speed.
(DC series motor)
Advantages of DC Motor

7.  Easy to understand design
- The design of the brushed DC motor is quite simple. A
permanent magnetic field is created in the stator by either of
two means:
 Permanent magnets
 Electro-magnetic windings
- If the field is created by permanent magnets, the motor is
said to be a "permanent magnet DC motor" (PMDC).
- If created by electromagnetic windings, the motor is often
said to be a "shunt wound DC motor" (SWDC).
Advantages of DC Motor

8.  High maintenance
- care required to maintain the mechanical interface
used to get current to the rotating field.
- maintenance includes the commutator (the
collection of copper and mica segments attached to
the rotor winding over which the brushes pass), and
the brushes themselves.
 Not suitable in very clean environment.
- vulnerable to dust which decreases
performance.
Disadvantages of DC Motor

10. AC Motor
 AC motor is an electric motor driven by
an alternating current.
 Commonly consists of two basic parts, an outside
stationary stator having coils supplied with
alternating current to produce a rotating magnetic
field, and an inside rotor attached to the output
shaft that is given a torque by the rotating field.
 Two main types of AC motors- depending on the
type of rotor used.
- the asynchronous motor
- the synchronous motor
Introduction

11.  AC motor has two basic electrical parts: a "stator"
and a "rotor“.
Operation of AC Motor
Rotor
Stator

12.  Principle of operation for all AC motors relies on
the interaction of a revolving magnetic field
created in the stator by AC current, with an
opposing magnetic field either induced on the
rotor or provided by a separate DC current so
urce.
 Resulting interaction produces usable torque,
which can be coupled to desired loads throughout
the facility in a convenient manner.
Operation of AC Motor

13.  Low cost
 Speed variation
 High power factor
 Reliable operation
Advantages of AC Motor

14. Advantages of AC Motor
 Low Cost
- Lowest cost motor for applications requiring more than
about 1/2 hp (325 watts).
- due to the simple design of the motor.
- For this reason, AC motors are preferred for fixed speed
applications in industrial applications and for commercial
and domestic applications where AC line power can be
easily attached.
- Over 90% of all motors are AC induction motors.
- Can be found in air conditioners, washers, dryers,
industrial machinery, fans, blowers, vacuum cleaners and
many other.

15.  Speed variation
- The fixed number of winding sets (known as poles) built
into the ac motor, which determines the ac motor's base
speed.
- The frequency of the AC line voltage. Variable speed drives
(Adjustable speed drives) change this frequency to change the
speed of the motor.
- The amount of torque loading on the motor, which causes
slip.
Advantages of AC Motor

16.  High power factor
- power factor of an AC electrical power system is defined
as the ratio of the real power flowing to the load to
the apparent power in the circuit.
- a load with a low power factor draws more current than a
load with a high power factor for the same amount of
useful power transferred.
- higher currents increase the energy lost in the distribution
system, and require larger wires and other equipment.
Advantages of AC Motor

17. Reliable Operation
-The simple design of the AC motor results in extremely
reliable, low maintenance operation.
-Unlike the DC motor, there are no brushes to replace.
-If run in the appropriate environment for its enclosure,
the AC motor can expect to need new bearings after
several years of operation. If the application is well
designed, an AC motor may not need new bearings for
more than a decade.
Advantages of AC Motor

18. Disadvantages of AC Motor
 Inability to operate at low speeds
- We know that standard AC motors should not be operated at
speeds less than about 1/3 of base speed. This is due to thermal
considerations. In fact a DC motor should be considered for these
applications.
 Poor positioning control
- Positioning control is expensive and crude with AC motors too.
Even a vector drive is very crude when controlling the standard AC
motor.
- Servo DC motors are more appropriate for these applications.

19. Disadvantages of AC Motor
 AC will produce eddy currents due to the production
of a back emf.
- Because motors are generators that operate in reverse, they
produce an emf just like generators do.
- Called as back emf and does not immediately appear when
a motor is initially turned on.
- The back emf is a consequence of Lenz's law, which states
that an induced emf produces a magnetic flux that resists the
change.
- Back emf works to reduce the current in the loop, thus
slowing the motor down, and it gets larger as the speed of the
motor increases.

20.  The advantages and disadvantages of DC and AC
motor somehow depends on application used.
• The reference of DC and AC refers how the
electrical current is transferred through and from
the motor. Both the types of the motors have
different functions and applications.
• However, AC motor is widely used in industry
application that support AC source voltage.
Conclusion