Induction motors are like the backbone of modern industry, playing a huge part in about one-third to one-half of all the electrical equipment we use in various industries today. They either serve as the main driving force or play a crucial role in the process. In this blog, we’ll cover the basics of what an induction motor is, how it works, and the different types of induction motors. This will give you a good overall idea about these important machines. Induction motors are actually the most common type of electric motors out there.
What is an Induction Motor?
So, induction motors work on the principle of electromagnetic induction. This means they generate an electric current in the rotor thanks to the magnetic field created by the windings in the stator. Basically, there are two main parts that make up an induction motor:
Stator: This is the stationary part of the machine. It has coils that create a rotating magnetic field when we apply an alternating current (AC) to it.
Rotor: This is the part that rotates and sits inside the stator. The rotor can either be of the squirrel cage type or the wound type.
The magnetic field from the stator interacts with the induced currents in the rotor, generating torque that turns the shaft through a backward-rotating magnetic field in the rotor.
How Does an Induction Motor Work?
The way an induction motor operates is based on Faraday’s law of electromagnetic induction and Lenz's law. Here’s a simple breakdown of how it all works:
AC Supply to Stator: When we apply an AC voltage to the stator windings, it creates a rotating magnetic field (RMF) around the stator. This field spins at a synchronous speed (Ns), which depends on the frequency of the AC supply and the number of poles in the motor.
Induction in the Rotor: The rotating magnetic field goes through the air gap and cuts across the rotor conductors. According to Faraday’s law, this induces an electromotive force (EMF) in those rotor conductors. Since the rotor is a closed circuit, currents start flowing in the rotor.
Production of Torque: The currents induced in the rotor create their own magnetic field, which interacts with the stator's rotating magnetic field. Thanks to Lenz's law, the rotor will start spinning in the same direction as the rotating magnetic field to minimize the relative motion between them. This interaction creates torque that makes the rotor turn.
Asynchronous Operation: The rotor never actually hits synchronous speed (which is the speed of the stator’s rotating magnetic field). If it did reach that speed, there would be no relative motion between the rotor and the magnetic field, meaning no induced EMF or current in the rotor. The difference between the synchronous speed and the rotor speed is what we call slip.
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