INDUCTION MOTOR

 

 Induction Motor(AC motor) :

                 An induction motor or asynchronous motor is an AC electric motor in which the electric current is the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding.

Types of Induction motor :

      The types of induction motors can be classified depending on whether they are a single phase (or) three phase induction motor.

Single Phase Induction motors :

1. Split Phase Induction motor
2. Capacitor Start Induction motor
3. Capacitor Start & Capacitor Run Induction motor
4. Shaded Pole Induction motor

Three Phase Induction motor :

1. Squirrel Cage Induction motor
2. Slip Ring Induction motor

Single Phase Induction motor

            The single phase induction machine is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps and so forth.

             The Single-Phase induction motor stator has a laminated iron core with two windings arranged perpendicularly.

• One is the main and other is the auxiliary winding or starting winding.

Construction of single phase induction motor -- Stator

Construction of single phase induction motor -- Squirrel cage rotor

                         

     

             This single phase induction motors are truely two phase machines.

    

             The motor uses a squirrel cage induction 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.

The single phase induction motor operation can be discussed by two methods :

• Double Rwvolving Field Theory ; and
• Cross Field Theory.

              Double revolving theory is perhaps the easier of the two explanations to understand.

•  A single phase ac current supplies the main winding that produces a pulsating magnetic field.
• Mathematically, the pulsating field,could be divided into two fields, which are rotating in opposite directions.
• The interaction between the fields and the current induced in the rotor bars generates opposing torque.
• Under these conditions, with only the main field energized the motor will not start.

• However , if  an external torque moves the motor in any direction, the motor will begin to rotate.
• Single-Phase motor main winding generates two rotating fields, which oppose and counter balance one another.

Applications of single phase induction motor :

            Single phase induction motors are used in smaller equipment where we require less horsepower (for example , one horsepower). Some of examples of real life are ---

• Pumps
• Compressors
• Small fans
• Mixers
• Toys
• High-speed vaccum cleaners
• Electric shavers
• Drilling machines.

               I hope that this blog is helpful to you.In the next blog we learn about Three Phase induction motor.

                    ***THANK YOU***