The document discusses single phase induction motors. It describes the construction of single phase induction motors, which have the same stator and rotor construction as three phase induction motors but with a single phase winding. It explains that a single phase induction motor does not self start due to the double revolving magnetic field set up by the single phase winding. It then discusses different methods to enable starting, including capacitor start motors, capacitor run motors, split phase motors, and shaded pole motors. Finally, it lists some common applications of single phase induction motors.

1. 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
Single Phase Induction Motor

2. 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
Construction – Stator
Stator: Same as 3 Phase IM but with single phase winding
Rotor: Same as 3 phase IM but only squirrel cage type.
Laminations
Slots
Stator Conductors
Stato
r
Rotor
bars
End rings
Rotor

3. 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
Working Principle
• Only one phase winding
• Field magnitude varies with that of excitation current
• Field set up acts in only one direction
 Represented by combined effect of two fields of equal
magnitude, rotating in opposite directions ie; Double
Revolving Field

4. Double Revolving Field Theory
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
Resultant field is alternating
Hence,
Single Phase induction motors are Not Self Starting in nature
Torque, Nm
Slip, %
00.511.52
Torque due to forward field TF
Torque due to reverse field TB
Resultant Torque

5. Starting
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
• One Phase winding, One field acting in one direction
• Necessitates one more field with lesser phase displacement
• Phase difference between two fields creates rotating magnetic
field
Two stator windings carrying currents that are phase displaced
Types
• Capacitor Start Motor
• Capacitor Run Motor
• Split Phase Motor
• Shaded Pole Motor

6. Capacitor Start Motor
101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
Main Winding
Rotor
Starting Winding
Capacitor
Centrifug
al
Switch
V
I1 Ist
Im
φst
φm
V
Is
t
Im
I1
• Centrifugal Switch opens the circuit when speed is near about
rated speed
• Capacitor present in circuit only at starting

7. 101 / 102 Basic Electrical Technology Dept of E & E, MIT Manipal
• Domestic Applications
 Pumps, Fans, Refrigerators, Washing
Machines
 Mixers, Grinders, Hair Drier, Electric Razor
• Commercial Applications
 Electric Saw, Electric Screw driver, Electric
Drill
Microwave oven, Computer Systems, Cars
Applications