Induction motors have been traditionally used as constant speed motors supplied by the ac power source. The most popular type is the 3phase, squirrelcage ac induction motor. However, the slip at which the maximum torque occurs changes with rotor resistance. 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.
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. The stator consists of a series of wire windings of very low resistance permanently attached to the motor frame. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. The sinusoidal stator phase currents fed in the stator coils create a magnetic field. Mod01 lec17 dynamic equations of induction machines. 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 methods for singlephase induction motor nptel. The rotor terminals are connected to three slip rings which turn with the. 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. Understand the principle and the nature of single phase and 3 phase induction machines.
The induction motor essentially consists of two parts. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. Noload and blocked rotor test on an induction machine aim. 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. Note down the machine ratings and calculate rated current of the machine noload test. Disconnect any mechanical load connected to the induction motor. As a voltage and a current is applied to the stator winding terminals. Ppt threephase induction motor electrical engineering. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. In an induction motor, the rotor rotates because of slip i. Different types of starters for induction motor nptel. If the induction motor is operating in the linear magnetic region, the lm is constant. The 3phase set of currents, each of equal magnitude and with a phase. Introduction to induction motor instrumentation and.
You should also make a dc measurement of stator winding linetoline resistance using a dmm. A wound rotor, has a 3phase winding similar to the stator winding. When the mechanical load is applied to induction motor which requires speed. In this project paper microcontroller based system to control speed of induction motor is developed using pulse width modulation technique 2. Then, equation 1 can be shown in terms of magnitude as. List and describe the more commonly used equipment in an electric substation. The induction motor is made up of the stator, or stationary windings, and the rotor. Induction machines 1 introduction the induction machine was invented by nikola tesla in 1888. Starting of 3 phase induction motors, high starting torque motors, speed. Circle diagram of an induction motor its construction. Speed control of induction motor using pwm technique. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. Nptel electrical engineering electrical machines ii.
Torque speed characteristics of induction motor slip. 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. Find the percentage slip and number of poles of the induction motor. It is logical that the least expensive, lowest maintenance type. The construction of the circle diagram is based on the approximate equivalent circuit shown below. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control. The threephase induction motor is the extensively used for various kinds of industrial drives. When the rotor resistance is increased, so is the slip for maximum torque, and the stable operating slip range of the. Before starting to explain how an induction asynchronous generator works, i assume that you know the working principle of an induction motor. 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. The voltage and current is induced in the rotor circuit from the stator circuit for the operation. Nptel syllabus electrical machines i video course course outline synchronous machines.
Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. Induction generators are also called as asynchronous generators. 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. Chapter 3 induction motor and different speed control methods page no 3. 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. Induction motor works on the principle of induction where electromagnetic field is induced into the rotor when rotating magnetic field of stator cuts the. Module 8 threephase induction motor version 2 ee iit, kharagpur lesson 29 rotating magnetic field in threephase induction. Electrical machines i video course electrical engineering nptel.
This document is highly rated by electrical engineering ee students and has been viewed 2535 times. 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. 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. 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. Umanand, principal research scientist, power electronics group, cedt, iisc bangalore for more details on nptel visit. Power from electric motor to driven is delivered by transmitting device.
Equivalent circuit of an induction motor enables the performance characteristics which are evaluated for steady state conditions. The rotor of an induction motor can be a squirrel cage rotor or wound. It is the diagrammatic representation of the performance of the induction motor. The basic difference is that the load is mechanical. The singlephase motor stator has a laminated iron core with two windings arranged perpendicularly. Schrage motor operation principle and characteristics of. Rotating and pulsating field, development of equivalent circuit based on double revolving field theory, torqueslip characteristic. It is logical that the least expensive, lowest maintenance type motor should be used most often. 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. The induced voltages emfs in stator winding and rotor barwinding, the. View notes l29nkdet ee nptel from eso 203 at iit kanpur. The rotor will constantly be turning to align its magnetic field with that of the stator field. 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. 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.
The basic idea of an electric motor is to generate two magnetic fields. Schrage motor is essentially a combination of wound rotor induction motor and frequency convertor. 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. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. The threephase induction motor behaves as a transformer whose secondary winding can rotate.
Mod01 lec17 dynamic equations of induction machines youtube. The advantages of threephase ac induction motor are listed below. This paper presents design and analysis of a three phase induction motor drive using igbt. 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. It supplies an induction motor ich has a full load speed of 144wh 0 rpm. May 04, 2020 ppt threephase induction motor electrical engineering ee notes edurev is made by best teachers of electrical engineering ee. Singlephase motors have only two power source supply lines connected.
Threephase induction motor, cage and wound slipring rotor, synchronous and rotor speed, slip, induced voltages in stator winding and rotor bar. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. Right from its inception its ease of manufacture and its robustness have made it a very strong candidate for electromechanical energy conversion. Nptel provides elearning through online web and video courses various streams. Schrage motor can be treated as an inverted poly phase induction motor. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control constant slip control fieldoriented control. An induction motor is based on the principle of induction of voltages and currents. 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. A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. An induction motor also known as an asynchronous motor is a commonly used ac electric motor. At the end of the lecture, student should be able to. Induction motor 1 chapter 3 induction motor bee23 electrical machine power system 2 learning outcomes. Differentiate between the various types of generating electric power stations. Unlike induction motor the primary winding of schrage motor is on the rotor.
Induction motor drives with closedloop control are used in similar applications to d. The induction motor plays very important role in industrial sectors, primarily due to its robustness and low cost. 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. Induction motors can be started directonline dol, which means that the rated.
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. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Perform an analysis on induction machines which is the most rugged and the most. The stator is supplied by a balanced 3phase ac power source.
Speed torque characteristics of induction motor from eq. 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. It is a maintenancefree, less noisy and efficient motor. Record all nameplate information for the induction motor. Ac induction motors are also the most common motors used in main powered home appliances. Three phase supply is given to the primary with the help of 3 slip rings. Simplified steadystateequivalent circuit of induction motor. 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. An induction motor is the most modest electrical machine from constructional point of view, in the majority of the cases. It is available from fractional horsepower ratings to megawatt levels. A 480v, 60 hz, 6pole, threephase, deltaconnected induction motor has the following parameters. Noload and blocked rotor test on an induction machine aim theory.
Fall 2005 ee595s electric drive systems 3 voltsperhertz control history. The induction motor stator resembles the stator of a revolving field, three phase alternator. Letting the rotor speed be r, we see immediately that if. Several additional components are necessary to operate the singlephase motor. 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 basics, single phase and three phase. Rotating magnetic field in threephase induction motor nptel. Aug 25, 2018 schrage motor is essentially a combination of wound rotor induction motor and frequency convertor.
In this module, containing six lessons 2934, mainly, the study of induction motors, fed from balanced threephase supply, will be described. Pdf speed control of induction motor using pi and vf. A motor with only armortisseur windings is called an induction motor. However, recently, it has been increasingly used as variable speed motors driven by an inverter. Torqueslip speed characteristics of induction motor nptel. Characteristically, linear induction motors have a finite primary or secondary length, which generates endeffects, whereas a conventional induction motor is arranged. It is a 16 bit highperformance digital signal controller dsc. Circle diagram of an induction motor the circle diagram of an induction motor is very useful to study its performance under all operating conditions.
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