Design of a three phase squirrel cage induction motor for. These motors can operate at any working conditions. I will tell you about the construction of wound rotor induction motor in the first section. Firstly, i am going to tell you about the structure of squirrel cage induction motor. Or they can be divided according to type of rotor i squirrel cage motor and ii slip ring motor or wound type. A squirrel cage induction motor does not contain brushes, slip rings and. As you can see, the 3 phase squirrel cage induction motor could achieve the electromechanical energy conversion simple and straight forward. The basic idea of an electric motor is to generate two magnetic fields. The implementation is done using a rectifier and an inverter, where the pwm triggering pulses were generated by using pic micro controller for switching the igbts of the inverter. When a 3 phase supply is given to the stator of an induction motor. Their sole purpose is to allow resistance to be placed in series with the rotor windings while. One of the simplest, most widely used electric motor explained. For squirrel cage rotor it consists of copper bars. The rotor is of the squirrel cage type and is under the influence of this moving field.
A squirrelcage rotor is the rotating part of the common squirrel cage induction motor. Wound rotor induction motors ac motors electronics textbook. Hence another starting method is used to start three phase induction motor called an autotransformer starter. 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. Afterwards i will cover the working principle and features of squirrel cage induction motor. Design of a three phase squirrel cage induction motor for electric propulsion system. When the double cage motor is running at normal speed, frequency of the rotor emf is so low that the reactance of both cages is negligible. The rotor is same as that employed in 3phase squirrel cage induction. Wound rotor induction motors chapter ac motors pdf version. The preferred method of speed control for squirrel cage induction motors is to vary the frequency of the supply voltage and the system used for this purpose is known as variable frequency drives or vfd. Explain starting methods of 3 phase induction motor. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. 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.
Some of the advantages, disadvantages and applications of squirrel cage induction motor compared with slipring induction motor are discussed below. Squirrel cage wound rotor with slip rings the rotating magnetic field. In this section, i will share the working of a squirrel cage induction motor with you guys. In essence, squirrel cage motors work no differently than most other induction motors and only differ in the specific interaction between rotor and stator. In operation, the nonrotating stator winding is connected to an alternating. Pdf improving squirrel cage induction motor efficiency. A simple explanation of squirrel cage induction motors. This is the basic working principle of induction motor of either type, single phase of 3 phase. Normally, we use the motors in industrial drives because they are rugged, reliable and economical. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor.
Starting method for induction motors a 3phase induction motor is theoretically self starting. A single phase induction motor is inherently not selfstaring can be shown easily. 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. The rotor is separated from the stator by a small airgap which ranges from 0. The reason for the name squirrel cage is because of the type of rotor used in these motors. Learn the working principle and applications of a squirrel cage induction. Construction of squirrel cage induction motor explained. A 3 phase induction motor has two main parts i stator and ii rotor. Advantages and disadvantages of squirrel cage induction motor. When the 3 phase supply is provided to the stator, a magnetic field is produced which rotates the rotor and motor starts.
Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. The torque speed characteristics of double squirrel cage motor for both the cages are shown in the figure below. Some of them are even fractional horsepower motors, which are used in applications like small toys, small fans, hairdryers etc. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. Working principle of an induction motor circuit globe.
The 3phase set of currents, each of equal magnitude and with a phase. For squirrel cage rotor it consists of copper bars, slightly longer than. The major difference between them is that transformer is static in nature i. Star delta starter and its working principle electrical. The stator of an induction motor consists of 3phase windings, which when connected to a 3phase supply creates a rotating magnetic field. This method of starting is quite popular for delta connected squirrel cage induction motor.
Join researchgate to find the people and research you need to help your work. Ac supply is given to stator winding, which produces a magnetic field that is rotating because of the time changing ac supply. The induction motor is started by itself that we know. A wound rotor induction motor is also known as slip ring induction motor. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. Induction generators induction motor operating as a generator consider a frictionless vehicle powered by a squirrel cage induction motor that is directly coupled to the wheels as the vehicle climbs a hill, the motor runs at slightly less than synchronous speed. Mar 25, 2020 squirrel cage induction motor started on full line voltage using d o l starter as a starting method draw very large starting current which can damage motor winding and also create a current surge on the power system.
Squirrel cage induction motor the engineering projects. 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. The principal advantages of the squirrel cage induction motor are its simplicity of design and robust construction. This article presents an understanding of what squirrel cage induction motors. For example, a 3600 rpm squirrel cage induction motor which delivers full load output at 3550 rpm as a motor will deliver full rated power as a generator at 3650 rpm if the hajfload motor speed is 3570 rpm, the output as a generator will be onehalf of rated value when driven at 3630 rpm, etc. The operating principles of induction machines and basic data concerning. C supply to stator winding flux generated in the stator winding. A motor rating of 10 horse power, 415 volts with 1440 rpm and 4.
Three phase slip ring induction motor my tech info. The rotor will constantly be turning to align its magnetic field with that of the stator field. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. 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. What is the working principle of slip ring induction motor. Pdf design of outer rotor single phase squirrel cage induction motor. Oct 28, 2015 the working principle of this servo motor is similar to the normal induction motor. Their sole purpose is to allow resistance to be placed in series with the. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Due to the similarities in working principle, the orspscim design is derived from the study of conventional single phase and three phase. In this method, the motor is first started as a star connected motor and as soon as the motor reaches near to or rated speed, it is it is run as delta connected motor.
Introduction cage rotor induction motor im is widely accepted as the most potential candidate for electric propulsion owing, to their reliability, robustness, less maintenance and ability to work in hostile environments. The schematic diagram of servo system for ac twophase induction motor is shown in the figure below. The stator of slip ring induction motor is very much the same as that of the squirrel cage induction motor, but the construction of its rotor is very much different. In the last sections, i will share some advantages and uses. The working principle of induction motor depends upon the electromagnetic induction. In the second section, i would be throwing light on the operation and working principle of wound rotor induction motor. There basically 2 types of induction motor depending upon the type of input supply i single phase induction motor and ii three phase induction motor. How an induction motor works by equations and physics introduction. This article will explain the principles of squirrel cage motors, how they. The rotating magnetizing field represented by the space vector b m or, equivalently by the magnetizing current i m moves at the synchronous speed. As soon as this torque starts to revolve the rotor, additional torque is produced by singlephase induction motor action. This rotating magnetic field has a speed which is known as the synchronous speed. Unlike a 3phase induction motor, a singlephase induction motor is not self starting but requires some starting means.
Thus the rotor rotates in the same direction as that of stator flux to minimize the relative velocity. Consequently, a small starting torque is developed. This will link and cut the rotor conductors which in turn will induce a current in the rotor conductors and. Different speed control methods of induction motor are explained below.
The rotor of shaded pole induction motors is the squirrel cage type rotor. Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction 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. An induction motor can therefore be made without electrical connections to the rotor. The two cages being connected in parallel, the combined resistance is lower. Speed control of three phase squirrel cage induction motor using vf method is implemented. A squirrel cage has got bars which are shorted by end rings. This is to obtain an optimum starting torque and for limiting the torque dip during the runup. Induction motor works on the principle of electromagnetic induction.
Shaded pole induction motors working and construction. Jul 25, 2019 squirrel cage induction motor working principle. What is autotransformer starter,working principle,diagram. We saw the working principle of squirrel cage induction motor which is the same in all induction motor. This is why the commonest induction motors are called squirrel cage motors. 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. In simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel. Vfd working principle a variable frequency drive controls the speed, torque, and direction of an ac induction motor. Again the controller must know the exact position of the rotor using encoder for precise speed and position control. Due to this flux rotor current induced and rotor flux also generated. The motor accelerates to a speed slightly below the synchronous speed and runs as a.
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. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Wound rotor induction motors ac motors electronics. The working principle of wound rotor induction motor is as same as in any other induction motor. 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. A 3 phase ac current passing through a stator winding produces a rotating magnetic field. 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. Types of ac induction motor rotors there are twotypes of rotor windings. The speed of rotating magnetic field is synchronous speed, n s r. An induction motors rotor can be either wound type or squirrel cage type.
This article explains the construction, working principle of singlephase induction motors. On the theory of 3phase squirrelcage induction motors. An induction motor s rotor can be either wound type or squirrel cage type. Squirrel cage induction motors are cheaper in cost compared to slip ring induction motors. The squirrel cage winding of a synchronous machine will generally be smaller than for an induction machine of similar rating.
A similar phenomenon also happens inside an induction motor. Aug 31, 2017 the invention of induction motors permanently altered the course of human civilization. Oct 10, 2016 working of a wound rotor induction motor. Working principle of 3 phase squirrel cage induction motor. Advantages of three phase squirrel cage induction motor. In normal conditions, the slip ring motor functions like a squirrel cage motor. One of the advantages of the slipring motor is that resistance may be inserted in the rotor circuit to obtain high starting torque at low starting current and then cut out to obtain optimum running conditions. Start delta starter is a scheme for motor starting to reduce the inrush current during starting of the motor. Also lets get to know the methods which are used to control the speed of squirrel cage. Wound rotor induction motor the engineering projects. How an induction motor works by equations and physics. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. Stator winding spreading the coil in this manner creates a sinusoidal flux distribution per pole, which improves performance and makes the motor less noisy sound and electrically. Fixed condensers capacitors are often used in place.
Squirrel cage induction motor working principle when a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. A synchronous motor may have a squirrel cage winding embedded in its rotor, used to increase the motor starting torque and so decrease the time to accelerate to synchronous speed. In the last sections, i will share some advantages and. This hundredyearold motorinvented by the great scientist nikola teslais the most common motor type.
In this chapter, we shall focus our attention on the construction, working and characteristics of commonly used singlephase motors. How are squirrel cage induction motors constructed. Synchronous speed means the speed of the rotating magnetic field in the stator. In squirrel cage induction motor starting torque is very low. In operation, the nonrotating stator winding is connected to an alternating current power source. When three phase supply is given to the stator winding, a rotating magnetic field of constant magnetic field is produced. A 3 phase ac induction motor photoed by hordu motor. I g crow beng, phd, ceng, fimeche, fimare, memasme, r robinson bsc, ceng, fiee, in plant engineers reference book second edition, 2002. Thus, the rotor will feel the torque that rotates the rotor in the direction of the rotating magnetic flux. There are two basic reasons for the use of singlephase motors rather than 3phase motors. General equations for squirrel cage induction motors are derived based on the real geometry of the motor.
Working principle of three phase induction motor electrical. However, the rotor never succeeds in catching up the synchronous speed. In short, the working principle of any induction motors involves stator flux and squirrel cage rotor flux. The working of the threephase induction motor is based on the principle of electromagnetic induction. By means of complex timedependent transformations free angles are introduced which simplify the set of equations when the specific geometrical properties of both types in which the asynchronous. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used. When the winding of stator are given a 3 phase ac supply, a current will start flowing through it. This arrangement is used for obtaining high starting torque at a low value of starting current. 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. Our article all about induction motors contains a discussion of the principal laws behind all induction motors and gives an understanding of how motion is created from magnetism. Learn what a three phase induction motor is, how it is constructed, and its working principle. These are also called as asynchronous motors, because an induction motor always runs at a speed lower than synchronous speed.
A single phase induction motor is very similar to a 3phase squirrel cage induction motor. Almost 95% of the induction motors used is of squirrel cage type. 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. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. A 1phase induction motor is similar to a 3phase squirrel cage induction motor in physical appearance. What is a squirrel cage motor and how does it work. Know how the speed control is easily achieved by changing the number of. The singlephase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner.
Here you will find squirrel cage induction motor working principle, construction, application and advantages of the squirrel cage induction motor. Oct 09, 2016 working of a squirrel cage induction motor. As induction motors are widely being used, their speed control may be required in many applications. Here we will learn how does single phase induction motor work. The speed of the rotor will depend on the ac power, and the speed can be controlled by changing the input supply power. Designing of three phase squirrel cage induction motor for. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. Here instead of a simple loop, something very similar to a squirrel cage is used. Construction, working one of the advantages of the slipring motor is that resistance may be inserted in the rotor circuit to obtain high starting torque at low starting current and then cut out to obtain optimum running conditions. This work is introducing the designing of new three phase squirrel cage induction motor with an objective of getting good efficiency. Induction motors are the most commonly used motors in many applications. But at the starting of the induction motor, starting current is very large which may damage motor windings.