Brief introduction of single phase induction motor and also introduce the types of induction motor

1. Subject :- DACM(2170909)
Topic :-TYPES OF SINGLE PHASE INDUCTION MOTOR
Guided by :- Prof Mahesh Patel
Electrical Department
Mishra Shweta 151040109009
Panda Shubhashree 151040109010
Thakkar Umang 151040109035
Parth Soni 151044109001
Submitted by :-

2.  Operating principle
The single-phase induction motor operation can be
described by two methods: –
Double revolving field theory;
Cross-field theory.

3. Why single phase IM is not self starting?
 The stator of a single phase induction motor is wound
with single phase winding.
 When the stator is fed with single phase supply, it
produced alternating flux (which alternates along one
space axis only).
 Alternating flux acting on a squirrel cage rotor can not
produce rotation , only revolving flux can.
 That’s why a single phase induction motor is not self
starting.

4. Starting torque
 The single-phase motor starting torque is zero of the
pulsating single-phase magnetic flux.
 The starting of the motor requires the generation of a
rotating magnetic flux similar to the rotating flux in a
three-phase motor.
 Two perpendicular coils that have currents 90° out of-
phase can generate the necessary rotating magnetic fields
which start the motor.
 Therefore, single-phase motors are built with two
perpendicular windings.
 The winding are starting winding (auxiliary winding) and
running winding (main winding)

5.  The phase shift is achieved by connecting
I. a resistance
II. an inductance
III. a capacitance in series with the starting winding.
 Most frequently used is a capacitor to generate the starting
torque.

6.  Single-phase induction motors are classified and named
according to the method employed to make them self-starting.
 (1) Split-phase induction motor : ( started by two phase
motor action through the use of an auxiliary and main
winding)
 (2) Capacitor motors : ( started by two phase motor action
through the use of an auxiliary and a capacitor)
(i) Capacitor-start induction motor
(ii) Capacitor run induction motor
(iii) Capacitor-start and Capacitor run induction motor
 (3) Shaded-pole induction motor :(started by the motion of
the magnetic field produced by means of shading coil around A
portion of the pole structure)

7. Split phase induction motor
 Two winding
 Main winding & auxiliary winding
 90 degree phase angle
 Main winding – low resistance and high reactance
 Aux winding - high resistance and low reactance
 Switch = motor pickup its 75 % of its rated speed.

8.  Working
I. Is lags by V because low reactance and high resistance
II. Im lags V by very large angle due to high reactance
III. Starting torque proportional to sin θ (Ts α Sin θ)
IV. Disconnect switch after reach its 75 % of rated speed
 Operation Centrifugal switch
It is connected in series with the auxiliary winding and
mounted on the rotor shaft. When the motor started and
reaches 75% of synchronous speed, CFS is mechanically
opened and in running condition auxiliary winding
remains cutout from the circuit.
 Therefore, the motor runs only with main winding.

9.  Characteristics
I. Starting torque – 1.5 times to 2 times the full load
torque.
II. Starting current – 6 to 8 times the full load current.
III. Operating power factor – 0.55 to 0.65.
IV. Efficiency – 60-65%
V. Power rating-(1/6 to 1/3 H.P)
VI. Speed near to 1440rpm
 Applications
It has low starting current and moderate starting torque. It
is used for easily started loads and typical applications
include fans, saws, washing machines, grinders, blowers
etc.

10.  Capacitor induction motor
1. Capacitor start motor
2. Permanent capacitor motor
3. Capacitor start capacitor run motor

11. Capacitor start motor
 Electrolytic capacitor
 Im lags V due to high reactance of main winding
 Due to capacitor Is lead V
 Im and Is angle 80 ˚to 90˚
 High starting torque

12.  Characteristics
o Starting torque- 3.5 to 4.5 times the full load torque
o θ-varies from 30˚ to 80˚ -Starting torque can be improved
o Power factor varies from 0.65 to 0.75
o Efficiency– 65 to 70%
o Power rating –1/8 to3/4 hp
 Applications
This motor has high starting torque and therefore is used
for hard start loads such as pumps, compressors,
refrigeration units, conveyors, certain machine tools etc.

13. Capacitor Run Motor
 Permanent capacitor is connected in series with starting
windings.
 Electrolytic capacitor not used.
 Rating of starting winding(auxiliary winding) and running
winding(Main winding) is equal.
 Starting torque is low.

14.  Characteristics
o Starting torque is lower about 50 to 100% of the full load
torque
o Power factor (high) varies from 0.75 to 0.80
o Efficiency– 75 to 80%
 Applications
This motor has low starting torque and therefore is used in
Ceilling fans, Room coolers, Table fans and other
domestic appliances.

15. Capacitor start, capacitor run motor
 A Capacitor Start Capacitor Run motor has two
Capacitors out of which one is used to make the motor
self-starting and another is used to improve its
performance while running i.e. increases it's power factor.
 Cs is Starting Capacitor in series with auxiliary winding
used to have phase displacement between Main winding
and Auxiliary winding nearly 90 degree or above 90.

16.  Characteristics
o Starting torque – 3 to 3.5 times the full load torque.
o Efficiency is improved
o Power factor-0.9 approx.
o Pull out torque- up to 260% of rated torque
 Applications
It combines the advantages of capacitor start and
permanent-capacitors and is used for hard to start loads
such as compressors, refrigerators, pumps, conveyors
etc.These motors are often employed requiring a quite
operating motor such as in hospitals, studios.

17. Shaded-pole induction motor
 Small motors requiring only small starting torque may be
made self-starting by using low resistance copper bands
called shading bands.
 The emf induced in the shading band causes a current to
flow in the band. This current opposes the change of flux
to which it is due and thus there is a time lag between the
fluxes in the shaded and unshaded portion of the pole.
 The flux in the shaded portion of the pole lags the flux in
the other portion. The results is like a rotating field
moving in the direction from the unshaded to the shaded
portion of the pole and a starting torque is produced

19.  Characteristics
o Low starting torque – 0.4 to 0.8 times the full load torque.
o Efficiency less -35% approx.
o Power factor poor - 0.45 approx.
o Pull out torque- 15% of full load torque.
o Power rating-1/300 to 1/20 HP (2.5W to 40W)
 Applications
Because of their poor starting torque, low power factor
and poor efficiency such motors are only suitable for low
power applications such as for toys, portable fans , electric
clocks, hair dryers, slide projectors, humidifiers, small
business machines such as photo copying machines,
vending machines, advertising displays etc.