# Explain How A Squirrel-Cage Rotor Produces A Magnetic Field

Explain How a Squirrel Cage Rotor Produces a Magnetic Field

This article explains how a squirrel-cage roton creates a magnetic field and how its laminations can be skewed to reduce ‘locking’ in a position between two magnetic fields. We also discuss the effects of rotor current on the magnetic field. It’s a fascinating topic that can help explain many aspects of squirrel-cage rotors.

## Creating a magnetic field in a squirrel-cage rotor

The squirrel cage rotor is an example of an induction motor. This type of motor uses a magnetic field induced by the stator’s rotating energy. The induced voltage creates a current that flows through the rotor bars and around the end ring. The speed of the current and the polarity of the rotor and stator determine the cutting action of the wire.

The rotor is the rotating part of an induction motor. The rotor is wound with two or three-phase windings. When the rotor turns, the magnetic field cuts the winding in two places and creates another one. This interaction results in torque. This torque is the result of the movement of the two magnetic fields. This mechanism can produce a powerful electric current.

The rotor of an IM can be made to have external resistance to increase its starting torque. However, it is impossible to achieve high starting torque with a squirrel cage motor without using external rotor resistance. Therefore, a double-sealed squirrel cage rotor is used to get high torque from an IM. During the rotation of the rotor, the current generated by the stator induces a magnetic field. During this rotation, the rotor pulls along with the rotating field and makes a rotation.

## Skewing rotor laminations reduces rotor ‘locking’ in a position between magnetic fields

The skewing of rotor laminations helps to reduce ‘locking’ of the rotary axis in between the magnetized fields. The laminations in the stator and rotor are arranged with 36 and 40 bars, respectively. The prime number of the rotor’s bars reduces feedback from the rotor.

A plurality of slots 202 are disposed in a rotor core 200. Each slot 202 includes a permanently magnetizable material located in a notch. These straight sections of the magnet are inserted into the slots and magnetized to form a selected number of poles. The slots are also covered with secondary conductors extending through the slots, and the slots are offset from the outer circumference of the rotor core.

In a ‘locking’ magnetic field, the rotor ‘locks’ in one position between two magnetic fields, and the magnetic field inside it moves backward. The ‘locking’ position of the rotor is prevented by the skewing of the rotor laminations. As a result, the ‘locking’ position is reduced to between two magnetic fields.

## Need for synchronous speed to produce a magnetic field in a squirrel-cage rotor

If we look at a squirrel-cage rotor, it appears inside the stator of a three-phase motor with four poles per phase, and the stator is connected to a 60-hertz line, the rotor produces an electromagnetic field induced in the slits and bars. The speed of the rotor, when in motion, produces a magnetic field around each bar and the slitting action cuts the wire. As the slitting action occurs, the rotor experiences zero tangential force, and the induced voltage is equal to the stator’s value of synchronous speed.

Another drawback of synchronous motors is their self-starting capability, which makes them unsuitable for many applications. A squirrel-cage rotor overcomes this problem by creating a magnetic field while interacting with a rotating magnetic field. Once inside the squirrel-cage, the rotor starts rotating. Since the squirrel-cage rotor has no self-starting capacity, it is a good choice for small motors.

## Effect of rotor current on the magnetic field in a squirrel-cage rotor

A three phase induction motor, which has no power supply, produces a varying magnetic field when it operates at synchronous speed. The current induced around the rotor windings is governed by Faraday’s law. When the rotor current is smaller than the impedance of the rotor windings, the rotor turns at a slower rate, producing a greater torque than the induced voltage.

The current flows through the rotor bars, causing a ring-like effect to form around each bar. The resulting magnetic field interacts with the magnetic field produced by the stator. As a result, the rotor field opposes the cause of the rotating magnetic field. Once the rotor catches the rotating magnetic field, the current flows down to zero, and the tangential force is zero.

The rotor current is induced by the magnetization of the rotor, which is a key component of a squirrel cage induction motor. The rotor is made of aluminum laminations with copper or aluminum conductors embedded in its surface. The magnetic field created by the rotor is caused by the interaction of the magnetic fields. Because the current in the rotor varies with the rotation rate of the stator, the magnetic field is generated.

## What is a squirrel-cage rotor?

A squirrel-cage rotor is an inductor with a cylindrical core of metal (usually aluminum) with radial conducting bars (the so-called “squirrel cage”) around the circumference arranged so that the conductor bars are shorted at the ends.

The squirrel-cage rotor is the most common type of induction motor rotor.

## How does a squirrel-cage rotor produce a magnetic field?

A squirrel-cage rotor produces a magnetic field by virtue of the current flowing through the conductor bars.

As the current flows through the conductor bars it creates a magnetic field that interacts with the magnetic field of the stator to produce torque.