Construction and working principle of single phase induction motor

Construction and working principle of single phase induction motor:

various electrical equipment used in offices, home appliances, lighting purpose, motors are work on ac supply.Hence instead of dc motors,the motor which work on ac supply are generally used. This ac motors  called as  single single phase induction motor.These motors single phase induction motors has  numerous domestic applications .The power rating of single phase induction motors are very small.  Some of motors are even fractional HP (horse power) motors,  which are generally used in applications like small toys,  small fans,  hair dryers etc. 
 

In this post we are discussing  different term like construction of single phase induction, working principle single phase induction motors, and applications of different types of single phase induction motors.

Construction of Single Phase Induction Motors: 

Construction of Single Phase Induction Motors same as  dc.  motor,  single phase induction motor has  two main parts as DC motor, one rotating which is called rotor and other stationary called stator.   The stator has laminated construction,  made up of stampings . to reduce eddy current loses. 

The stampings has slots on its periphery to carry the stator winding or also called as main winding. This is  stator winding excited by a single phase ac supply.  The laminated construction of stator has advantages  which reduced iron losses .  The stampings are made up of material like silicon steel which minimises the hysteresis loss.  The stator winding is wound for certain definite number of poles means when excited by single phase ac.  supply,  stator produces the magnetic field.  The number of poles for which stator winding is wound,  decides the synchronous speed of the motor. 

 

fig: construction of single phase induction motor
pic credit: learnengineering.com

The synchronous speed is denoted by Ns and it has  relation with supply frequency f and number of poles P.
As given below

 

Fig single phase induction motor speed

Induction motor never rotates with synchronous speed but its rotate speed less than synchronous speed which is slightly less than synchronous speed Ns

The rotor construction is squirrel cage type. Rotor has uninsulated copper or aluminum bars which are shorted at the both end with the help of end ring entire assembly look like cage, hence called as squirrel cage rotor.
The resistance of entire rotor is very very small, the air gap between stator and rotor kept uniform and as small as possible.

Working Principle of single phase induction motors:

For motoring action there must be exist two fluxes which interact with each other to produce torque, which is necessary to rotate rotor.

In single phase induction motors ac supply given to the stator winding. Which produces alternating flux called as main flux.  This flux link with the rotor conductor and due to transforming action emf get induced in rotor bar. The induced EMF drives current through rotor as rotor are short circuit act as closed circuit.this rotor current produced another flux called rotor flux which is required for motoring action. As the second flux in produced by induction action hence the motor is called induction motor.

In DC motor separate supply are required to armature to produced armature flux, this is main difference in the DC motor and induction motor
 

Another main difference is dc motors are self starting but single phase induction motors are not self starting

Different Types of single phase induction motor:

• Split phase induction motor.
• Capacitor start inductor motor.
• Capacitor start capacitor run induction motor ( two value capacitor method).
• Permanent split capacitor (PSC) motor .
• Shaded pole induction motor.

Various applications of single phase induction motor:

1.single phase induction motors are used in air conditioner and refrigerator

2.Ceiling fan and blowers.

3.Machine tool drive.

4.Pump drive

5.Vacuum cleaner

6.Blowers