Squirrel cage motor low rotor resistance low starting torque centrifugal pumps, wood working tools etc. Oct 10, 2016 working of a wound rotor induction motor. The threephase induction motor the squirrelcage induction motor the woundrotor induction motor 3 4. C supply to stator winding flux generated in the stator winding. The schematic diagram of servo system for ac twophase induction motor is shown in the figure below. These are of two types, squirrel cage and slip ring motors. In operation, the nonrotating stator winding is connected to an alternating current power source. Working principle of an induction motor circuit globe. Thus from the working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. The rotor will constantly be turning to align its magnetic field with that of the stator field. Squirrel cage construction, the rotor winding consists of a number of rotor bars, shortcut by rings from both side, see figure below. We do not require to give external starting torque for starting induction motor but the starter is provided with an induction motor for limiting starting current. Most of the application of industrial as well as domestic are this type of induction motor. In this work a conventional three phase squirrelcage type induction motor with specifications 10 hp, 415v, stardelta connected and 4 poles is chosen for comparison with our motor, which is designed for good efficiency.
The working principle of wound rotor induction motor is as same as in any other induction motor. The squirrelcage induction motor linkedin slideshare. The singlephase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner. Mainly we discuss a threephase squirrel cage induction motor. This article presents an understanding of what squirrel cage induction motors. The basic idea of an electric motor is to generate two magnetic fields. This rotating magnetic field has a speed which is known as the synchronous speed. In the last sections, i will share some advantages and. 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 three phase squirrel cage induction motor. These motors fill most generalpurpose, constantspeed drive requirements. Again the controller must know the exact position of the rotor using encoder for precise speed and position control.
What is a squirrel cage motor and how does it work. Considering a cycle of alternating current fig 1 applied to the stator winding we will explain the working of shaded pole motor. In simple words, the induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. Working of double squirrel cage motor at starting of the motor, frequency of induced emf is high because of large slip slip frequency of rotor emf supply frequency.
The rotating magnetizing field represented by the space vector b m or, equivalently by the magnetizing current i m moves at the synchronous speed. Learn what a three phase induction motor is, how it is constructed, and its working. Squirrel cage motor high rotor resistance high starting torque compressors, crushers, reciprocating pumps etc. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. This article will explain the principles of squirrel cage motors, how they. These motors can operate at any working conditions. The reason for the name squirrel cage is because of the type. Differentiate between the various types of generating electric power stations. The relative motion between this field and the rotation of the rotor induces electric current in the conductive bars.
There basically 2 types of induction motor depending upon the type. This hundredyearold motorinvented by the great scientist. 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. Threephase squirrelcage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. An induction motor s rotor can be either wound type or squirrel cage type. Oct 09, 2016 afterwards i will cover the working principle and features of squirrel cage induction motor.
In normal conditions, the slip ring motor functions like a squirrel cage motor. Know about the different classes of squirrel cage induction motors introduction we have seen the classification of a. The working principle of this servo motor is similar to the normal induction motor. Pdf torquespeed characteristics of three phase squirrel.
Squirrel cage induction motor an overview sciencedirect. In the case of three phase ac alternating current operation, the most widely used motor is a 3 phase induction motor, as this type of motor does not require an additional starting device. In this article, we will learn about squirrel cage and slip ring induction motors. The stator has windings that produce a magnetic field, and windings on the rotor cut this field and induce a current in the rotor windings. List and describe the more commonly used equipment in an electric substation.
An induction motors rotor can be either wound type or squirrelcage type. Due to this flux rotor current induced and rotor flux also generated. In the last sections, i will share some advantages and uses. The ruggedness and simplicity of the squirrel cage induction motor usually makes it the first choice for a driver.
If the speeds become equal, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. The working principle of induction motor depends upon the electromagnetic induction. In simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. Know how the speed control is easily achieved by changing the number of stator poles. The three phase induction motors are simple in construction, rugged, low cost and easy to. The basics how capacitors work working principle duration. Threephase ac induction motors are widely used in industrial and commercial applications. A 3 phase induction motor has two main parts i stator and ii rotor. Once the motor attains the normal speed, the brushes are shortcircuited, and the wound rotor works as a squirrel cage rotor. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. These types of motors are known as selfstarting induction motors. Horizontal squirrel cage mediumvoltage induction motor. A 3 phase ac induction motor photoed by hordu motor.
Squirrel cage motor higher rotor resistance higher starting torque. What is the working principle of slip ring induction motor. Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. Nov 27, 2019 thus from the working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. Starting of squirrel cage induction motors485 an induction motor can be regarded as a transformer with a small air gap in the magnetic circuit. Three phase induction motor is a generally selfstarting motor. These motors are having the difference in rotor construction.
Oct 28, 2015 the working principle of this servo motor is similar to the normal induction motor. The conversion process is electromagnetic induction. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. How are squirrel cage induction motors constructed. We saw the working principle of squirrel cage induction motor which is the same in all induction motor. However, should the motor require service, this manual includes a section that assists the. The reason for the name squirrel cage is because of the type of rotor used in these motors. The field windings in the stator of an induction motor set up a rotating magnetic field through the rotor. An induction motor is an electrical motor whic does not require external excitation of the rotor.
The squirrel cage induction motor is the most commonly used motor in industry. Working principle of three phase induction motor electrical. The invention of induction motors permanently altered the course of human civilization. These motors are selfstarting and use no capacitor, start winding, centrifugal switch or other starting device. They are particularly suited for applications where the motor. Aug 31, 2017 the invention of induction motors permanently altered the course of human civilization. When a 3 phase supply is given to the stator of an induction motor. Squirrel cage induction motors are cheaper in cost compared to slip ring induction motors. Also lets get to know the methods which are used to control the speed of squirrel cage. Pdf improving squirrel cage induction motor efficiency. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. This hundredyearold motorinvented by the great scientist nikola teslais the most common motor type. This arrangement is used for obtaining high starting torque at a low value of starting current.
Most industries use squirrel cage induction motor with a starter for starting purpose. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. The 3phase set of currents, each of equal magnitude and with a phase. These are also called as asynchronous motors, because an induction motor always runs at a speed lower than synchronous speed. In operation, the nonrotating stator winding is connected to an alternating. 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. It is low cost and requires low maintenance in comparison with other motor types. We do not require to give external starting torque for starting induction motor but the starter is provided. For squirrel cage rotor it consists of copper bars, s lightly longer than. A squirrel cage induction motor does not contain brushes, slip rings and. Some of the advantages, disadvantages and applications of squirrel cage induction motor compared with slipring induction motor are discussed below. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Lecture 6 three phase induction motors cairo university. Normally, we use the motors in industrial drives because they are rugged, reliable and economical.
An induction motor can therefore be made without electrical connections to the rotor. Thus, principle of 3 phase induction motor also explains why rotor rotates in same direction as the rotating field and why induction motor is self starting. 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. 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. A double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. An electrical motor is an electromechanical device which converts electrical energy into mechanical energy. Squirrel cage induction motor the engineering projects. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. Jul 25, 2019 squirrel cage induction motor working principle. Induction motors are the most commonly used motors in many applications. A squirrel cage rotor is the rotating part of the common squirrel cage induction motor. Induction motor basics, single phase and three phase. When rotor winding is shortcircuited with no resistance in series, it is called a squirrel cage induction motor and when rotor winding is shorted through a resistance in series, it is. It converts electrical energy into mechanical energy and it is used to provide motion.
It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Synchronous speed means the speed of the rotating magnetic field in the stator. Designing of three phase squirrel cage induction motor for. Afterwards i will cover the working principle and features of squirrel cage induction motor. Working principle of 3 phase squirrel cage induction motor. Wound rotor induction motor the engineering projects.
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 squirrel cage secondary winding on the other member usually the rotor carries induced current. Squirrel cage induction motors are commonly used in many industrial applications. Torquespeed characteristics of three phase squirrel cage induction motor aim. Construction of squirrel cage induction motor explained. Pdf three phase squirrel cage induction motor, conctruction. A single phase induction motor is very similar to a 3phase squirrel cage induction motor. The ruggedness and simplicity of the squirrelcage induction motor usually makes it the first choice for a driver. 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. Unlike a 3phase induction motor, a singlephase induction motor is not self starting but requires some starting means. Advantages and disadvantages of squirrel cage induction motor.
Ac supply is given to stator winding, which produces a magnetic field that is rotating because of the time changing ac supply. The working of the threephase induction motor is based on the principle of electromagnetic induction. The rotor is separated from the stator by a small airgap which ranges from 0. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. When threephase stator winding of an induction motor is energized from a 3 phase supply, a rotating magnetic field is set up which rotates around the stator at synchronous speed n s. Explain starting methods of 3 phase induction motor. There are two basic reasons for the use of singlephase motors rather than 3phase motors. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. Shaded pole induction motors working and construction.
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