Electric motors defined as electromechanical devices that convert electrical energy to mechanical energy. The mechanical energy can be used to perform work such as rotating a pump impeller, fan, blower, driving a compressor, lifting materials etc. Ultimately, motors are the interface between the electrical and mechanical systems of a facility. So, EM are an important part of any electrical system. They used throughout every manufacturing plant,office and home consuming about 70% of all electricity generated. That’s why electric motors are termed as “Work Horse” in an industry.
Electrical current flowing in a loop of wire produce a magnetic field acros the loop. When this loop is surrounded by the field of another magnet,the loop will turn, producing a force (called torque) that results in mechanical motion.
Parts of the Motor- 1.Armature or rotor 2.Commutator 3.Brushes 4.Axle 5.power supply of some sort for example- battery The contacts of the commutator are attached to the axle of the electromagnet, so they spin with the magnet.
There are numerous ways to design a motor, thus there are many different types of motors and each type possess different operating characteristics. Based on this characteristics the motor can be chosen for a specified application. We will try to explain the main types of motors and For this explanation, I am calling md mukhlesur Rahman and giving thanks to all. Allah hafez.
The stator is in the stationary electrical component. The rotor is the rotating electrical component, which in turn rotates the motor shaft. There are two types of AC motors: synchronous (see figure) and induction. The main difference between the synchronous motor and the induction motor is that the rotor of the synchronous motor travels at the same speed as the rotating magnetic field.
Stator:The stator is in the stationary electrical component. rotor: The stator is in the stationary electricalthat speed is more difficult to control for AC motors. component. The rotor is the rotating electrical component, which in turn rotates the motor shaft.
Their popularity is due to their simple design, they are inexpensive (half or less of the cost of a DC motor) High power to weight ratio (about twice that of a DC motor) easy to maintain can be directly connected to an AC power source
Ac motors and their types
AC Motors & Their Types
Electromechanical device that converts electrical
energy to mechanical energy.
Mechanical energy used to e.g.
Rotate pump impeller, fan, blower
Motors in industry: 70% of electrical load.
What is an Electric
An electric motor is all about magnets and
magnetism: A motor uses magnets to create motion.
A motor is consist of two magnets.
Classification of Motors
Alternating Current (AC)
Direct Current (DC)
Alternating Current (AC)
Electrical current reverses direction
Two parts: stator and rotor
Stator: stationary electrical component
Rotor: rotates the motor shaft
• Synchronous motor
• Induction motor
Induction motors can be classified into two
single-phase induction motors
three-phase induction motors
Single-phase induction motors:
These only have one stator winding, operate with a
single-phase power supply...
Three –phase induction motors:
The use three sets of stator coils the rotating
magnetic field drags the rotor around with it.
•Induction motors are the most common motors used for
various equipments in industry.
• Squirrel cage
• Wound rotor
Single Induction motor
•Single phase motors are very widely used in
home, offices, workshops etc. as power
delivered to most of the houses and offices is
single phase. In addition to this, single phase
motors are reliable, cheap in cost, simple in
construction and easy to repair.
3 phase Induction Motor
As its name indicate stator is a stationary part of induction motor. A
three phase supply is given to the stator of induction motor.
The rotor is a rotating part of induction motor. The rotor is connected to
the mechanical load through the shaft. The rotor of the three phase
induction motor are further classified as
• Squirrel cage rotor
• Slip ring rotor or wound rotor or phase wound rotor
• Advantages of squirrel cage induction rotor
1. Its construction is very simple and rugged
2. as there are no brushes and slip ring, these
motors requires less maintenance.
Squirrel cage induction motor is used in lathes, drilling
machine, fan, blower printing machines etc
Slip Ring Induction Motor
• Slip ring or wound three phase induction motor : In this
type of three phase induction motor the rotor is wound
for the same number of poles as that of stator but it has
less number of slots and has less turns per phase of a
heavier conductor.The rotor also carries star or delta
winding similar to that of stator winding. The rotor
consists of numbers of slots and rotor winding are
placed inside these slots.
• Advantages of slip ring induction motor
1. It has high starting torque and low starting
2. Possibility of adding additional resistance to
Slip ring induction motor are used where high
starting torque is required i.e in hoists, cranes,
As the name suggests
Synchronous motors are
capable of running at
constant speed irrespective
of the load acting on them.
Synchronous motors have
got higher efficiency than
its counterparts. Its
efficiency ranges from 90 –
AC Synchronous motor
Stator: It carries three phase winding and is fed from 3-phase
Rotor: It carries permanent magnet poles that rotate exactly
with same speed as that of the stator magnetic field, hence
the name synchronous motor.
It is not self starting.
The rotor acting as a bar magnet will turn to line up
with the rotating magnet field. The rotor gets locked to the
RMF and rotates unlike induction motor at synchronous speed
under all load condition
Speed at which RMF rotates or Synchronous speed can easily
be derived as follows,
speed of synchronous motor can be very
accurately controlled. This is the reason why
they are suitable for high precision
Why Synchronous motors are not self starting ?
North Pole of the Rotor will obviously
get attracted by South Pole of RMF,
and will start to move in the same
direction. But since the rotor has got
some inertia, this starting speed will
be very low. So it will give repulsive
force. This will make the rotor move
backward. As a net effect the rotor
won’t be able to start.
Making Synchronous Motor Self Start
• To make synchronous motor self start, a squirrel cage
arrangement is cleverly fitted through pole tips. They are
also called as damper windings.
At the starting rotor field coils are not energized.
So with revolving magnetic field, electricity is
induced in squirrel cage bars and rotor starts
rotating just like an induction motor starts.
Out of Synchronism
•Synchronous motors will produce constant speed
irrespective of motor load only if the load is within
the capability of motor. If external torque load is
more than torque produced by the motor, it will slip
out of synchronism and will come to rest. Low supply
voltage and excitation voltage are other reasons of
going out of synchronism
Application of Synchronous
• Synchronous motor having no load connected to its shaft is used for
power factor improvement. it is used in power system in situations
where static capacitors are expensive.
• Synchronous motor finds application where operating speed is less
(around 500 rpm) and high power is required. For power requirement
from 35 kW to 2500KW, the size, weight and cost of the
corresponding induction motor is very high. Hence these motors are
preferably used. Ex- Reciprocating pump, compressor, rolling mills etc