Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase induction. It supplies an induction motor ich has a full load speed of 144wh 0 rpm. May 31, 2019 a linear induction motor or lim is a special type of induction motor used to achieve rectilinear motion rather than rotational motion as in the case of conventional motors. Induction motors im are widely used in the industrial application due to a high powerweight ratio, high reliability and low cost. Massachusetts institute of technology mit opencourseware. We return to the elementary model of the induction motor. Induction generators are also called as asynchronous generators. Lecture 6 three phase induction motors cairo university. The 3phase set of currents, each of equal magnitude and with a phase. Electrical engineering electrical machines ii nptel. It is logical that the least expensive, lowest maintenance type motor should be used most often. 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. The main winding of a single phase induction motor produces a magnetic field. Loganathan umanand, does not currently have a detailed description and video lecture title.
Induction machines guru nanak dev engineering college, ludhiana. General theory of induction motors nptel one, used for threephase induction motor will be presented. An843, speed control of 3phase induction motor using pic18 mcus. Threephase induction motor, cage and wound slipring rotor, synchronous and rotor speed, slip, induced voltages in stator winding and rotor barwinding. I have written only those lectures which i found important and which are in the gate syllabus. Such an induction motor with integrated brake is shown on figure 1. Specific emphasis will be given to pump applications. Starting methods for singlephase induction motor nptel. It is available from fractional horsepower ratings to megawatt levels. Induction motors ppt transformer electrical engineering.
Vectorcontrolled induction motor drives the previous control strategies good steadystate but poor dynamic response oscillation resulted from the air gap flux vector control fieldoriented control is related to the phasor control of the rotor flux. For this motors, we require three phase power supply, whereas thus three phase power must be supplied in a sequence. Sms with a 4pole rotor operated at 50hz rotate in synchronism with the supply at exactly 1500rpm. The induction motor stator resembles the stator of a revolving field, three phase alternator. Vf speed control of 3 phase induction motor using space. Mutilevel converterfed induction motor drive utility friendly induction motor drive 02 03 03 02 01 01 4 control of synchronous motor self controlled synchronous motor vector control of synchronous motor 02 02 nptel. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. Speed control of induction motor using pwm technique.
In addition, electronics can reduce the systems average power consumption and noise generation of the motor. Right from its inception its ease of manufacture and its robustness have made it a very strong candidate for electromechanical energy conversion. Find the percentage slip and number of poles of the induction motor. The lighting distribution panels are the source for singlephase power supply.
There are two basic reasons for the use of singlephase motors rather than 3phase motors. Umanand, principal research scientist, power electronics group, cedt, iisc bangalore for more detail. May 20, 2020 ppt threephase induction motor electrical engineering ee notes edurev is made by best teachers of electrical engineering ee. The stator frame consists of laminations of silicon steel, usually with a thickness of about 0. It has two ends, one is called driving end and another is called non driving end. A tutorial in ac induction and permanent magnet synchronous motors, vector control with digital signal processors, fred flett, analog devices, 1994. Record all nameplate information for the induction motor. Induction motor control is complex due to its nonlinear characteristics. A three phase induction motor is basically a constant speed motor so its somewhat difficult to control its speed. The winding wound on the stator of three phase induction motor is also called field winding and when this winding is excited by three phase ac supply it produces a rotating magnetic.
Menu of essential motor data defining the electrical model the program uses the motor data in the motor menu to generate the impedances of the motor. Its value is at least twice the fullload value when the motor is operated at rated voltage and frequency. Nptel electrical engineering electrical machines ii. Linear induction motors are quite an engineering marvel, to convert a general motor for a special purpose with more or less similar working principle, thus enhancing its. 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. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. So obviously the speed of an induction motor can be controlled by varying any of three factors namely supply frequency f, number of pole p or slip s. 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. Nptel syllabus advanced electric drives video course course outline.
Chapter 3 induction motor and different speed control methods page no 3. Basic electrical technology nptel online videos, courses. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control constant slip control fieldoriented control. 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 three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Speed control of a three phase induction motor using pwm. Course content the course content is in a pdf file induction motor theory. Single phase induction motors have very high starting torque.
Characteristically, linear induction motors have a finite primary or secondary length, which generates endeffects, whereas a conventional induction motor is arranged. These notes has been made by me after watching nptel lectures given by various professor from different iits and iisc. This is a rotating machine, unlike the transformer, described in the previous. 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. In an induction motor, the rotor rotates because of slip i. Both the ends are connected with bearings for free rotation.
What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy to mechanical energy, and vice versa. The speed control of three phase induction motor is essential because the motor control industry is a dominant sector. Instead it is a cylindrical core constructed of steel laminations with conductor bars mounted parallel to the shaft. The threephase induction motor behaves as a transformer whose secondary winding can rotate. If you have watched this lecture and know what it is about, particularly what electrical engineering topics are discussed, please help us by commenting on this video with your suggested description and title. These motors are suitable for all general applications where an open machine is not applicable due to severe environments such as excessive dirt, dust andor moisture. For variable speed drives, the source is normally an inverter that uses power. Introduction to induction motor instrumentation and control. The the useful motor relationships between time, current, speed, power factor and torque can be obtained from the analysis of the. The corre sponding induction motor im however, has slip losses and rotates only at 1475rpm for a chosen 30 kw example.
Before starting to explain how an induction asynchronous generator works, i assume that you know the working principle of an induction motor. It is the diagrammatic representation of the performance of the induction motor. Induction motor testing and evaluation summary as energy costs rise, more emphasis is being placed on determining the health of large inductive motors. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. Induction motor theory a pdh online course for engineers. For most shore facility applications, this is the case. Mechanical load is connected on driving end while cooling fan is connected on nondriving end. Firstly the equivalent circuit is developed on the basis of double revolving field theory when only its main winding is energized. In many cases, the singlephase motors on board a ship will be wired into the lighting distribution panels. A space vector pwm svpwm is utilized for pwm controlling scheme. Singlephase motors have only two power source supply lines connected. Various starting methods used in the singlephase induction motors, with the intro duction of additional features, like the addition of another winding in the stator. Ac induction motor fundamentals by rakesh parekh, microchip technology inc 9 induction motor protection and starting by viv cohen circuit breaker industries, p.
One well known approach is the utilization of synchronous motors sm. Equivalent circuit of a single phase induction motor. Induction machines 1 introduction the induction machine was invented by nikola tesla in 1888. List and describe the more commonly used equipment in an electric substation. These currents produce the rotor magnetic field, which interacts with the stator magnetic field, and produces torque, which is the useful mechanical.
The electric motor speed is fixed when ac motor is connected to ac line. Single phase induction motor double revolving field theory the threephase induction motor starting torque inversely depends on the slip this implies that a small positive slip 0. In this project paper microcontroller based system to control speed of induction motor is developed using pulse width modulation technique 2. Nptel handwritten notes these notes has been made by me after watching nptel lectures given by various professor from different iits and iisc. Torqueslip speed characteristics of induction motor nptel.
This tutorial will introduce the user to the fundamental electrical and mechanical principles of ac electric induction motor design and application. Speed control of three phase induction motor electrical4u. Ppt threephase induction motor electrical engineering. These slots should not be equal in number because if they are, there is a good chance that the motor will not start at all due to a characteristic known as cogging. This video lecture, part of the series basic electrical technology by prof. Nptel video lectures, iit video lectures online, nptel youtube lectures, free video lectures, nptel online courses. The laminations are insulated from each other usually by a varnish layer. Induction motors have been traditionally used as constant speed motors supplied by the ac power source. Any mechanical load applied to the motor shaft will introduce a torque on the motor shaft.
Lamination is necessary since a voltage is induced along the axial length of the steel as well as in the stator conductors. Differentiate between the various types of generating electric power stations. The previous control strategies good steadystate but poor. Pdf speed control of induction motor using pi and vf. Transformer dc machines induction machine power system power electronics analog electronics prof. Fall 2005 ee595s electric drive systems 3 voltsperhertz control history. Teco totally enclosed fan cooled squirrelcage induction motors are designed, manufactured and tested to meet or exceed the latest nema, ieee, csa and other international standards. As we will show, it does take a little e ort and even some computation to do the controls right, but this is becoming increasingly a ordable. Electric motor electric motor construction of induction motors.
In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The motor characteristics can be approximated by calculations using an equivalent circuit for the motor and using a series of formulas. For induction motors a very important parameter is the slip of the motor the slip, s, defines the relative speed difference between synchronous speed and rotor speed and is given by. Ac induction motors how ac motors work explain that stuff. Synchronous motors controlled by variablespeed drives are. The basic idea of an electric motor is to generate two magnetic fields.
The basic difference is that the load is mechanical. Depending on the class and application of the motor, the locked rotor torque can take on values of 0. An induction motor also known as an asynchronous motor is a commonly used ac electric motor. Singlephase induction motor, starting torque, main and auxiliary windings, starting methods, splitphase, capacitor type, motor with capacitor startrun. 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. Consider the working of a motor for a better understanding of these indicators. Induction motors have a series of slots in the stator and in the rotor. The rotor will constantly be turning to align its magnetic field with that of the stator field. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors. At noload, the slip is nearly zero induction motor drives s.
Difference is that transformer is an alternating flux machine while induction motor is rotating flux machine. However, recently, it has been increasingly used as variable speed motors driven by an inverter. 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. Equivalent circuit of a single phase induction motor the equivalent circuit of a single phase induction motor can be obtained by two methods named as the double revolving field theory and cross field theory. Induction motor driving a centrifugal compressor advantages n simple and rugged design n low cost n higher starting torque capability n minimal maintenance industry standards wem manufactures synchronous motors to meet all current industry standards including nema mg 1, ieee 112, iec 60034, api 541 and iso 9001 standards. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. Out of the a number of methods of speed control of an induction such as pole changing, frequency variation, variable rotor resistance, variable stator voltage, constant vf control, slip recovery method etc. Rotating flux is only possible when 3 phase voltage or poly phase which is 120 degree apart in time is applied to a three phase winding or poly phase winding 120 degree apart in space then a three phase rotating magnetic flux is. Single phase induction motor 1introduction the singlephase induction machine is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth. The main methods employed for speed control of induction motors are as follows.
This document is highly rated by electrical engineering ee students and has been viewed 2578 times. A three phase, 12 pole, salient pole alternator is coupled to a diesel engine running at 500 rpm. Singlephase induction motor the winding used normally in the stator fig. The induction motor is made up of the stator, or stationary windings, and the rotor. 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. Several additional components are necessary to operate the singlephase motor. The rotating stator magnetic field induces currents in the short circuited rotor. 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.
The construction of the circle diagram is based on the approximate equivalent circuit shown below. Electric motor construction of induction motors britannica. Circle diagram of an induction motor its construction. Fall 2005 ee595s electric drive systems 2 overview of strategies voltsperhertz control.
Target motor theory 4 3phase ac induction motor vector control motorola 3. Circle diagram of an induction motor the circle diagram of an induction motor is very useful to study its performance under all operating conditions. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Speed control of induction motors the speed of an induction motor is given as n 120fp 1s. Lecture series on basic electrical technology by prof. This torque is related to the motor output power and the rotor speed and out. Nptel provides elearning through online web and video courses various streams. The rotor of an induction motor can be a squirrel cage rotor or wound type rotor.