Basics of Induction Motors

Induction motors are used in 90% of electrical power industries. In this section, you'll learn about basics of Induction motors.

After going through this post you'll be able to:
  1. Learn the types of Induction Motors and their applications
  2. Concept of Speed
  3. Slip
  4. Induction motor formulas

Types of Induction Motors and their Applications

Induction motors are of two types:
  1. Squirrel cage
  2. Wound rotor
The internal design and construction of both are not discussed (You can simply read them from your theory books 😄).

A Squirrel cage motor has a very good speed regulation and it is used in places where the load is varying.

On the other hand, a wound motor provides high starting torque with a small starting current.

Speed of Induction Motor

The induction motor has two main parts.
  1. Stator: The stationary parts
  2. Rotors: The rotating part
The stator of an induction motor contains 3 'single phase windings'. When three currents pass through these windings at an angle of 120 degrees a rotating magnetic field is generated. This rotation of field is known as the synchronous speed. While using the term, 'speed of the motor' we mean this synchronous speed. This speed depends on the frequency and number of poles and is mathematically defined by the formula:

Slip Speed

The rotor of induction motors always rotates slower than synchronous speed. The term slip is used to explain the difference between these two speeds.
𝜂slip = 𝜂sync - 𝜂m


Common formulas which you should know:

So that was all about Induction motors, Learn more about Basics of Electrical Engineering theory.

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