In 1888, the scientist Nikola Tesla discovered the induction motor. Among the electric motors, the induction motor is the most popular. In practical terms, it is widespread, convenient to start and stop, easy to control the speed and change the direction of rotation, which is the main reason for its increase in use. From daily work at home to large factories and industries, almost all motors are induction motors.
Classification of induction motors:
There are two types of induction motors: –
1. Single-phase induction motor
2. Three-phase induction motor
Single-phase induction motor:
A single-section electric powered motor makes use of a single-phase energy supply to convert electric powered energy into mechanical electricity. It’s had wires one is phase and and one impartial cord. It generates an alternate field and for startup to needs a capacitor. A Single Phase motors had generally 1H.P to 2H.P .
Starting Technique:-
The armature of a single-phase ac motor has two windings. One is the starting winding and the other is the running or main winding. A capacitor is connected in series with the starting winding. Since both the windings of the motor are inductive without capacitor connection, the starting torque of the motor is zero as both the coils are in the same phase and there is no phase difference. As a result, the motor cannot be turned on. The use of the capacitor is created phase difference between two coils. As a result, the starting torque is produced and the motor turned around.
Speed control method: – Additional resistance is provided in the circuit by connecting a variable series resistance or a regulator in series with the ac motor. Then the speed is controlled by increasing or decreasing the voltage applied to the terminals of the motor by changing the resistance. This is a very simple method.
Advantage of single-phase ac motor: – a) Easy to connect b) low cost c) low maintenance cost d) High usage e) easy to change direction of rotation of motor.
Disadvantages: – a) Motor power is low, b) Motor efficiency is low c) starting torque is zero d) power factor is poor e) motor cannot start by itself.
Use of single-phase ac motor:
- Generally, single phase ac motors are used for various purposes in homes, offices, courts, schools, colleges and businesses.
2. Single phase ac motors are used to drive drill machines, grinding, lathe machines etc.
3. Various sizes of single-phase ac motors are used in industries to drive fans, refrigerators, air coolers etc.
Three Phase Induction AC Motor
A motor which is supplied with three phase AC and rotates on induction principle is called three phase induction motor. Three phase induction motor basically has two parts. A stator in which three phase AC supply is given and the other rotor in which thick copper bars are placed and their two ends are tightly sorted with the help of rings.