1. 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. 
Single phase electric motors can be classified as:
Single phase induction motor
1.Split phase, 2. Capacitor shaded pole
2. A.C Series motor or Universal Motor
3 . Repulsion motor
1. Repulsion –start Induction run motor Repulsion induction motor
4. Synchronous motor
1. Reluctance Motor 2. Hysteresis Motor
Drawbacks
Lack of starting torque
Reduced Power Factor
Low Efficiency

2. Principle of Operation of Induction Motor
In principle of operation of induction motor, rotating magnetic field rotates at synchronous speed interacts with rotor , this will produce torque that will make the rotor rotates at mechanical speed.
In three-phase induction motor, the rotating magnetic field is generated by applying three currents shifted by 120 degrees to three windings also shifted by 120 degrees.
In single-phase induction motor, there are many types based on method of starting, these types are:

3. Why is Three Phase Induction Motor Self Starting?
In three phase system, there are three single phase line with 120° phase difference. So the rotating magnetic field is having the same phase difference which will make the rotor to move.
Why Single Phase Induction Motor is not Self Starting?
When Single phase supply is fed to the stator winding, it produces only an alternating flux i.e. one which alternates along one space axis only. Due to this starting torque is zero. Hence motor does not rotate.

4. DOUBLE-FIELD REVOLVING THEORY
According to this theory, a pulsating field of a single-phase motor can be resolved into two rotating field of half its amplitude rotating in opposite direction at synchronous speed.
Electrical Machines

5. DOUBLE-FIELD REVOLVING THEORY
Electrical Machines

6. DOUBLE-FIELD REVOLVING THEORY
The torque–slip curve is shown below
Electrical Machines

7. Double – Field Revolving Theory

8. Single Phase Induction Motor
Applications:
The single-phase induction machine is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth.

10. Construction (STATOR)
Construction of Single Phase induction motor are stator and rotor.
The single-phase motor stator has a laminated iron core with two windings, One is the main winding and the other is the auxiliary winding or starting winding

11. Construction (ROTOR)
The motor uses a squirrel cage rotor, which has a laminated iron core with slots.
Aluminum bars are molded on the slots and short-circuited at both ends with a ring.

12. Why the rotor slots of a 3-phase induction motor are skewed?
The rotor slots of a three -phase induction motor are skewed
i). to make the motor run quietly by reducing the magnetic hum
ii). to reduce the locking tendency of the rotor
State the advantages of skewing?
It reduces humming and hence quite running of motor is achieved. It reduces magnetic locking of the stator and rotor.

15. Principle of Operation of Induction Motor1
Split-phase induction motor. 2
Capacitor start induction motor. 3
Permanent-split capacitor motor.
In this type the auxiliary winding and the capacitor are connected from the motor after starting 4
Capacitor start capacitor run motor.
In this type two capacitors are used with the auxiliary winding, one for starting and the other during start and run.

16. Split phase Induction motor
High reactance
Low Resistance
High Resistance
Low reactance
The motor has a starting torque of 100−200% of full load torque, with the starting current as 5-7 times the full load current.
Applications: fan, saw, small lathe, centrifugal pump, blower, office equipment, washing machine, etc.

17. Capacitor start induction motor
Applications: Compressor, Conveyor, Machine tool drive, Refrigeration and Air-conditioning equipment, etc.

18. Capacitor start capacitor run induction motor
Using two capacitors, the performance of the motor improves both at the time of starting and then running. This motor is used in applications, such as compressor, refrigerator, etc.
The power factor of this motor, when it is operating (running), is high.
This motor is used in applications, such as ceiling fans, air circulator, blower, etc.
Because of constant torque, the motor is vibration free and can be used in: (a) hospitals (b) studios and (c) other places where silence is important.

19. Shaded Pole Motor

20. What is the purpose of shading coil in the shaded pole motor?
The copper shading coil is used to produce rotating magnetic field moving from the unshaded to shaded portion of the pole, hence the motor produces a starting torque

24. The motor has low efficiency and is usually available in a range of 1/300 to 1/20 kW.
It is used for domestic fans, record players and tape recorders, humidifiers, slide projectors, small business machines, etc.
The shaded-pole principle is used in starting electric clocks and other single-phase synchronous timing motors.