Shaded pole induction motors working and construction. Diagnostics of rotor and stator problems in industrial. Consider a three phase squirrel cage induction motor whose stator has three windings displaced in space by 120 when they are excited with currents that are. The field windings in the stator of an induction motor set up a rotating magnetic field through the rotor.
Also lets get to know the methods which are used to control the speed of squirrel cage. Squirrel cage motor high rotor resistance high starting torque compressors. Various method have been developed for obtaining starting torque in these motors. The threephase induction motor is the extensively used for various kinds of industrial drives. So s1f1s2f2, and at starting the slip is equal to 1, so a unique value of. In induction motors, particularly squirrel cage type induction motors, sometimes exhibit a tendency to run stably at speeds as low as oneseventh of their synchronous speed ns. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. When the winding of stator are given a 3 phase ac supply, a current will start flowing through it. An induction motors rotor can be either wound type or squirrelcage. Designing squirrel cage rotor slots with high conductivity james l.
A squirrelcage induction motor is one in which the secondary circuit consists of a. Pdf three phase squirrel cage induction motor, conctruction. The stator winding carries an alternating current which produces the flux which is also alternating in nature. Its torquespeed and currentspeed characteristics are such that, on starting. How are squirrel cage induction motors constructed. Pdf squirrel cage induction motor design and the effect of. Double cage rotor of an induction motor a double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. Using variable voltage variable frequency vvvf drive. An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. A squirrel cage induction motor therefore draws a very high starting. Oct 09, 2016 working of a squirrel cage induction motor. Advantages of three phase squirrel cage induction motor. Squirrel cage induction motor the engineering projects.
Rotor is the part which distinguishes it from other induction motors. Working of shaded pole induction motor the operation of the motor can be understood by referring to the figure which shows one pole of the motor with a shading coil. These motors fill most generalpurpose, constantspeed drive requirements. An induction motor is an alternatingcurrent motor in which a primary winding on one member usually the stator is connected to the power source and a polyphase secondary winding or a squirrelcage secondary winding on the other member usually the rotor carries induced current. Some of the advantages, disadvantages and applications of squirrel cage induction motor compared with slipring induction motor are discussed below. These motors can operate at any working conditions. Stator of this motor is the same as the one used in squirrel cage induction motors. Squirrel cage induction motors are commonly used in many industrial applications.
Horizontal squirrel cage mediumvoltage induction motor. Or they can be divided according to type of rotor i squirrel cage motor and ii slip ring motor or wound type basic working principle of an induction motor in a dc motor, supply is needed to be given for the stator winding as well as the rotor winding. The ruggedness and simplicity of the squirrel cage induction motor usually makes it the first choice for a driver. Learn more about working of a synchronous motor here. Physical layout of induction motor in an induction motor induction refers the field in the rotor is induced by the stator currents and asynchronous refers that the rotor speed is not equal to the stator speed. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. This rotating magnetic field has a speed which is known as the synchronous speed this rotating magnetic field induces the voltage in rotor bars and hence shortcircuit currents start flowing in the rotor bars. This article presents an understanding of what squirrel cage induction motors are. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. Lecture 6 three phase induction motors cairo university. An induction motor also known as an asynchronous motor is a commonly used ac electric motor.
This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. Cheap copare to slipring im maintainance is easy cost is less compare to slipring im can use at explosive area starting torque is low compare to slip ring im application. For a fullload operating slip of 3 per cent, the speed will then be 1. The slots are not made parallel to each other but are bit skewed skewing is not shown in the figure of squirrel cadge rotor beside as the skewing prevents magnetic locking of stator and. They are particularly suited for applications where the motor. Jul 16, 2018 using variable voltage variable frequency vvvf drive. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable.
In operation, the nonrotating stator winding is connected to an alternating current power source. Squirrel cage induction motor an overview sciencedirect. A slip ring, three phase induction motor rotates at a speed of 1440rpm, when a supply of 400v, 50hz is applied across the stator terminals. The reason for the name squirrel cage is because of the type of rotor used in these motors. Squirrel cage induction motor an overview sciencedirect topics. The construction of stator of the induction motor is almost the same as other motors. A motor rating of 10 horse power, 415 volts with 1440 rpm and 4pole is selected for design problem and an equivalent circuit model is developed to find out the various performance parameters like efficiency, starting torque, torque. Difference between synchronous motor and induction motor. This phenomenon is known as crawling of an induction motor and the speed is called as crawling speed. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space.
A squirrel cage rotor is the rotating part of the common squirrel cage induction motor. The basic idea of an electric motor is to generate two magnetic fields. Mar 09, 2018 in this article, we will learn about squirrel cage and slip ring induction motors. Construction of squirrel cage induction motor explained. This phenomenon is known as crawling of an induction motor and the speed is. This arrangement is used for obtaining high starting torque at a low value of starting current. The rotor is constructed using a number of single bars shortcircuited by end rings and arranged in a hamsterwheel or squirrel cage configuration. Watch this video and learn basics of squirrel cage induction motor. In this section, i will share the working of a squirrel cage induction motor with you guys. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Most of the application of industrial as well as domestic are this type of induction motor.
Unlike a 3phase induction motor, a singlephase induction motor is not self starting but requires some starting means. Designing of three phase squirrel cage induction motor for. A 1phase induction motor is similar to a 3phase squirrel cage induction motor in physical appearance. Advantages and disadvantages of squirrel cage induction motor. Torquespeed characteristics of squirrel cage induction motor. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. Considering a cycle of alternating current fig 1 applied to the stator winding we will explain the working of. Synchronous motor always runs at a speed equal to its synchronous speed.
The rotor will constantly be turning to align its magnetic field with that of the stator field. In simple words, the induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. This flux links with the rotor conductors and due to transformer action e. Motors employing this type of rotor are known as squirrel cage inductionmotors. Wound rotor induction motor the engineering projects.
Studying and improving of squirrel cage induction motor scim efficiency is a continuous area of interest not only among the researchers but also the industry, manufacturer and government. How an induction motor works by equations and physics introduction. Polyu bse induction motors principle operation and torquespeed. Squirrel cage rotor almost 90 per cent of induction motors are squirrel cage type.
Stator winding is modified or split into two parts, to make it self start. An induction motor can therefore be made without electrical connections to the rotor. When voltage is applied to the stator winding, a rotating magnetic field is established. A three phase induction motor is a type of ac induction motors which operates on three phase supply as compared to the single phase induction motor where single phase supply is needed to operate it. This is why the commonest induction motors are called squirrel cage motors. Jul 25, 2019 squirrel cage induction motor working principle. These motors are selfstarting and use no capacitor, start winding, centrifugal switch or other starting device. But the rotor construction differs with respect to the type of motor. Starting of squirrel cage induction motors485 an induction motor can be regarded as a transformer with a small air gap in the magnetic circuit. The slip ring motor has very little application in industries. Consider the working of a motor for a better understanding of these indicators. Keeping the vf ratio constant, when frequency is reduced then that results in constant slipfrequency at running. The rotor of an induction motor can be a squirrel cage rotor or wound.
Motors employing this type of rotor are variously known asphasewound motors or wound motors or as slipring motors. Squirrel cage motor low rotor resistance low starting torque centrifugal pumps, wood working tools etc. The rotating magnetizing field represented by the space vector b m or, equivalently by the magnetizing current i m moves at the synchronous speed. Let me give you a brief idea of stator first and then i will tell you about the structure of rotor. The reason for the name squirrel cage is because of the type. The implementation is done using a rectifier and an inverter, where the pwm triggering pulses were generated by using pic micro controller for. A double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. The 3phase set of currents, each of equal magnitude and with a phase. Know how the speed control is easily achieved by changing the number of stator poles.
Dec 10, 2015 watch this video and learn basics of squirrel cage induction motor. Threephase ac induction motors are widely used in industrial and commercial applications. The rotor is constructed using a number of single bars shortcircuited by end rings and arranged in a hamsterwheel or squirrelcage configuration. The rotor is same as that employed in 3phase squirrel cage induction. How are high starting torques obtained in a squirrel cage. These motors are having the difference in rotor construction. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm.
The most popular squirrel cage induction motor is of a 4pole design. Induction motor is one of the most important motor used in industrial applications. Normally, we use the motors in industrial drives because they are rugged, reliable and economical. When the stator is fed with two or three phase ac supply, a rotating magnetic field rmf is produced. However, should the motor require service, this manual includes a section that assists the. In my last article, we have discussed squirrel cage induction motor which is a type of 3 phase induction motor. The singlephase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner.
Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. Squirrel cage induction motors are cheaper in cost compared to slip ring induction motors. For this motors, we require three phase power supply. In this article, we will learn about squirrel cage and slip ring induction motors. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. Telecommunication engineering, southwest jiaotong university, china, 2005 thesis submitted for the degree of masters of engineering science in school of electrical and electronic engineering the university of adelaide, australia august 2010. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. The relative motion between this field and the rotation of the rotor induces electric current in the conductive bars.
An induction motor s rotor can be either wound type or squirrel cage type. Ac induction motors are also the most common motors used in main powered home appliances. What is a squirrel cage motor and how does it work. Designing squirrel cage rotor slots with high conductivity. How an induction motor works by equations and physics. The ruggedness and simplicity of the squirrelcage induction motor usually makes it the first choice for a driver. Speed control of three phase squirrel cage induction motor using vf method is implemented. In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. Hence single phase induction motors are not self starting. The squirrel cage induction motor is the most popular type of ac motor. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. A 3 phase ac induction motor photoed by hordu motor. Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor.
The three phase supply current produces an electromagnetic field in the stator winding which leads to generate the torque in the rotor winding of three phase induction motor having magnetic field. Oct 10, 2016 hi friends, i hope you are fine and having fun. Pdf improving squirrel cage induction motor efficiency. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. By far the most commonly used ac motor is the induction motor.
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