Hence, to reduce this relative motion, the rotor starts rotating in the same direction as that of the stator field and tries to catch it but, can never catch it due to friction and windage and therefore emf induction continues and motor keeps rotating. You should also make a dc measurement of stator winding linetoline resistance using a dmm. If the induction motor is operating in the linear magnetic region, the lm is constant. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. The threephase induction motor is the extensively used for various kinds of industrial drives. Induction motor drives with closedloop control are used in similar applications to d. Induction machines 1 introduction the induction machine was invented by nikola tesla in 1888. In an induction motor, the rotor rotates because of slip i. Unlike induction motor the primary winding of schrage motor is on the rotor. Mod01 lec17 dynamic equations of induction machines youtube. Besides, the reluctance to the magnetic field is greater on account of the presence of the airgap across which the stator power is transferred to the rotor. Starting methods for singlephase induction motor nptel.
The sinusoidal stator phase currents fed in the stator coils create a magnetic field. Nptel syllabus electrical machines i video course course outline synchronous machines. Schrage motor is essentially a combination of wound rotor induction motor and frequency convertor. An induction motor also known as an asynchronous motor is a commonly used ac electric motor.
Ppt threephase induction motor electrical engineering. The induction motor essentially consists of two parts. The rotor of an induction motor can be a squirrel cage rotor or wound. Nptel provides elearning through online web and video courses various streams. As a voltage and a current is applied to the stator winding terminals. The rotor terminals are connected to three slip rings which turn with the. Simplified steadystateequivalent circuit of induction motor. Before starting to explain how an induction asynchronous generator works, i assume that you know the working principle of an induction motor.
Circle diagram of an induction motor its construction. Induction motors have been traditionally used as constant speed motors supplied by the ac power source. However, recently, it has been increasingly used as variable speed motors driven by an inverter. Module 8 threephase induction motor version 2 ee iit, kharagpur lesson 30 construction and principle of operation of im version 2 ee iit, kharagpur in the previous, i. The singlephase motor stator has a laminated iron core with two windings arranged perpendicularly. The voltage and current is induced in the rotor circuit from the stator circuit for the operation. View notes l29nkdet ee nptel from eso 203 at iit kanpur. Understand the principle and the nature of single phase and 3 phase induction machines. When the rotor resistance is increased, so is the slip for maximum torque, and the stable operating slip range of the.
Starting of 3 phase induction motors, high starting torque motors, speed. The advantages of threephase ac induction motor are listed below. Induction motor basics, single phase and three phase. It is a 16 bit highperformance digital signal controller dsc. Umanand, principal research scientist, power electronics group, cedt, iisc bangalore for more details on nptel visit. Speed control of induction motor using pwm technique. 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.
Different types of starters for induction motor nptel. Letting the rotor speed be r, we see immediately that if. Just like a dc machine, a same induction machine can be used as an induction motor as well as an induction generator, without any internal modifications. Single phase induction motor the singlephase induction machine is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth. Right from its inception its ease of manufacture and its robustness have made it a very strong candidate for electromechanical energy conversion. A 480v, 60 hz, 6pole, threephase, deltaconnected induction motor has the following parameters. The 3phase set of currents, each of equal magnitude and with a phase.
Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. An induction motor is based on the principle of induction of voltages and currents. Several additional components are necessary to operate the singlephase motor. Induction motors can be started directonline dol, which means that the rated. Schrage motor operation principle and characteristics of. A linear induction motor lim is an alternating current ac, asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. Induction motor 1 chapter 3 induction motor bee23 electrical machine power system 2 learning outcomes. Electrical machines i video course electrical engineering nptel. Characteristically, linear induction motors have a finite primary or secondary length, which generates endeffects, whereas a conventional induction motor is arranged. Equivalent circuit of an induction motor enables the performance characteristics which are evaluated for steady state conditions. This paper presents design and analysis of a three phase induction motor drive using igbt. An induction motor always operates at a speed lower than the synchronous speed because the rotating magnetic field that occurs in the stator will generate flux in the rotor that will cause the rotor to rotate, but due to the delay of the flow current in the rotor with current flow in the stator, the rotor will never reach its rotating magnetic field speed, that is, the synchronous speed. A wound rotor, has a 3phase winding similar to the stator winding.
It is a maintenancefree, less noisy and efficient motor. Three phase supply is given to the primary with the help. Circle diagram of an induction motor the circle diagram of an induction motor is very useful to study its performance under all operating conditions. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. The induction motor stator resembles the stator of a revolving field, three phase alternator.
Perform an analysis on induction machines which is the most rugged and the most. An induction motor is the most modest electrical machine from constructional point of view, in the majority of the cases. Aug 25, 2018 schrage motor is essentially a combination of wound rotor induction motor and frequency convertor. However, the slip at which the maximum torque occurs changes with rotor resistance. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The induced voltages emfs in stator winding and rotor barwinding, the. Record all nameplate information for the induction motor. Mod01 lec17 dynamic equations of induction machines. Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. Induction motor totallyenclosed fancooled nema standard epact three phase induction motors sdesign versatility teco totally enclosed fan cooled squirrelcage induction motors are designed, manufactured and tested to meet or exceed the latest nema, ieee, csa and.
Induction motors despite the fact that the threephase motor has more phases than the singlephase motor, the singlephase motor is a much more complex machine. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. Synchronous motor drives are close competitors to induction mo tor drives in many industrial applications. When the mechanical load is applied to induction motor which requires speed. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. Rotating magnetic field in threephase induction motor nptel. The most popular type is the 3phase, squirrelcage ac induction motor. Induction motor works on the principle of induction where electromagnetic field is induced into the rotor when rotating magnetic field of stator cuts the. The induction motor plays very important role in industrial sectors, primarily due to its robustness and low cost. The stator or the stationary part consists of three phase winding held in place in the slots of a laminated steel core which is enclosed and supported by a cast iron or a steel frame as shown in fig. Starting of 3 phase induction motors, high starting torque motors, speed control, rheostatic method, pole changing method, cascade control of speed, double cage induction motor, cogging an d crawling of induction motor, induction generator.
Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. At the end of the lecture, student should be able to. Differentiate between the various types of generating electric power stations. Noload and blocked rotor test on an induction machine aim. Pdf speed control of induction motor using pi and vf.
Singlephase motors have only two power source supply lines connected. It is available from fractional horsepower ratings to megawatt levels. The supply is connected to the stator and the rotor received power by induction caused by the stator rotating flux, hence the motor obtains its name induction motor. Find the percentage slip and number of poles of the induction motor. Noload and blocked rotor test on an induction machine aim theory. It is logical that the least expensive, lowest maintenance type. Schrage motor can be treated as an inverted poly phase induction motor. Then, equation 1 can be shown in terms of magnitude as. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. It is the diagrammatic representation of the performance of the induction motor. The basic idea of an electric motor is to generate two magnetic fields. Speed torque characteristics of induction motor from eq. Module 8 threephase induction motor version 2 ee iit, kharagpur lesson 29 rotating magnetic field in threephase induction. An induction motor is practically a constant speed motor, that means, for the entire loading range, change in speed of the motor is quite small.
These drives are also particularly suited to applications that must operate at very high speeds with a high level of field weakening, for example spindle motors. Torqueslip speed characteristics of induction motor nptel. A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. Singlephase induction motor threephase induction motor singlephase induction motor there are probably more singlephase ac induction motors in use today than the total of all the other types put together. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. Speed of a dc shunt motor can be varied very easily with good efficiency, but in case of induction motors, speed reduction is accompanied by a corresponding loss of efficiency and poor power factor.
Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. The bars forming the conductors along the rotor axis are connected by a thick metal ring at the ends, resulting in a short circuit as shown in figure 1. It is logical that the least expensive, lowest maintenance type motor should be used most often. Disconnect any mechanical load connected to the induction motor.
Rotating and pulsating field, development of equivalent circuit based on double revolving field theory, torqueslip characteristic. Nptel electrical engineering electrical machines ii. The basic difference is that the load is mechanical. List and describe the more commonly used equipment in an electric substation. In this module, containing six lessons 2934, mainly, the study of induction motors, fed from balanced threephase supply, will be described. There are two basic reasons for the use of singlephase motors rather than 3phase motors. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control constant slip control fieldoriented control. Power from electric motor to driven is delivered by transmitting device. Torque speed characteristics of induction motor slip. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control. The rotor will constantly be turning to align its magnetic field with that of the stator field. They are generally more expensive than induction motor dri ves,but the advantages is that the efficiency is higher,which is tends to lower the life cycle cost.
The stator is supplied by a balanced 3phase ac power source. In this project paper microcontroller based system to control speed of induction motor is developed using pulse width modulation technique 2. Threephase induction motor, cage and wound slipring rotor, synchronous and rotor speed, slip, induced voltages in stator winding and rotor bar. Three phase supply is given to the primary with the help of 3 slip rings. Fall 2005 ee595s electric drive systems 3 voltsperhertz control history. This document is highly rated by electrical engineering ee students and has been viewed 2535 times. The threephase induction motor behaves as a transformer whose secondary winding can rotate. The construction of the circle diagram is based on the approximate equivalent circuit shown below. The stator consists of a series of wire windings of very low resistance permanently attached to the motor frame. Note down the machine ratings and calculate rated current of the machine noload test. Introduction to induction motor instrumentation and. Chapter 3 induction motor and different speed control methods page no 3. The induction motor is made up of the stator, or stationary windings, and the rotor. Moduleiv 10 hours single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of parameters methods of starting, split phase starting, repulsion starting, shaded pole starting, performance characteristics.
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