Three-Phase Induction motors are self-starting motors and due to this there is no capacitor, start winding, centrifugal switch, or another starting device. Three-phase AC induction motors are widely used in industrial and commercial applications.
Types of 3 Phase Induction Motor
A 3-phase induction motor has two essential components and they are the stator which is the stationary part of the motor and the rotor is the rotating part of the motor. The load is connected to the shaft. Three-phase armature winding is wound over the stator. Once balanced 3- phase current supplies through the winding, then a stable amplitude rotary magnetic field is formed within the air gap.
This armature winding can be connected toward the three-phase power supply & carries the load current. The 3 phase induction motor is classified into two types based on its construction.
Squirrel Cage Induction Motor
The construction of the squirrel cage induction motor is extremely simple. its functions are based on the principle of electromagnetism. This rotor is a cylinder of steel laminations, with highly conductive metal embedded into its surface. A rotating magnetic field is produced, when an alternating current is run through the stator windings. A current is induced in the rotor winding, which produces its magnetic field. The stator produce interaction of the magnetic fields and rotor windings produces a torque on the squirrel cage rotor
These motors include rotors of bars in place of the rotor winding where these bars are fabricated with brass, aluminum otherwise copper. the biggest advantage of the squirrel cage motor is that its speed-torque characteristics can change by simply adjusting the shape of the bars in the rotor. As they are reliable, self-starting, and easy to adjust they are widely used in industries.
Wound Rotor or Slip Ring Induction Motor
The slip ring induction motor or wound rotor motor is also known as an asynchronous motor as the operating speed and the synchronous speed of a rotor not equal. The rotor of this type of motor is wound type that is why it is also called a wound rotor induction motor. A laminated cylindrical core is included in the rotor of this motor. The rotor winding is placed inside the slots. In the wound rotor, the insulated windings are wound on top of the rotor similarly like on the stator. The winding of this rotor is usually connected in the STAR model and can be distributed uniformly.