What is an Induction motor?
An induction motor (also known as an asynchronous motor) is a commonly used AC electric motor. In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding.
The rotor of an induction motor can be a squirrel cage rotor & wound type rotor.
Induction motors are referred to as ‘asynchronous motors’ because they operate at a speed less than their synchronous speed. So first thing to understand – what is synchronous speed?
Synchronous speed
Synchronous speed is the speed of rotation of the magnetic field in a rotary machine, and it depends upon the frequency and number poles of the machine. The induction motor always runs at speed less than its synchronous speed. The rotating magnetic field produced in the stator will create flux in the rotor, hence causing the rotor to rotate. Due to the lag between the flux current in the rotor and the flux current in the stator, the rotor will never reach its rotating magnetic field speed.
Types of induction Motor
There are basically two types of induction motor.
- Single phase induction motor
- Three phase induction motor
Single phase induction motors are not a self-starting motor and three phase induction motor are a self-starting motor.
Single phase induction Motor
The different types of single phase induction motor are :
- Split Phase Induction Motor
- Capacitor Start Induction Motor
- Capacitor Start and Capacitor Run Induction Motor
- Shaded Pole Induction Motor
Three phase induction Motor
The diffrent types of three phase induction motor are :
- Squirrel Cage Induction Motor
- Slip Ring Induction Motor
what is a self-starting motor?
When the motor starts running automatically without any external force applied to the machine, then the motor is referred to as ‘self-starting’. For example, we see that when we put on the switch the fan starts to rotate automatically, so it is a self-starting machine. Point to be noted that fan used in home appliances is a single phase induction motor which is inherently not self-starting. How? Does a question arise as to how it works? We will discuss it now.
Working principle of induction Motor
Basic working principle of an Induction Motor is The relative speed between stator RMF and rotor conductors causes an induced emf in the rotor conductors, according to the Faraday's law of electromagnetic induction. The rotor conductors are short circuited, and hence rotor current is produced due to induced emf.
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