Single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of. The construction of stator of the induction motor is almost the same as other motors. Some changes in the stator may be encountered when a slip ring motor is used in a cascaded system, as the supply for the slave motor is controlled by the supply from the rotor of the other slip ring motor with external resistance mounted on its rotor. A woundrotor motor, also known as slip ring rotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. No load and blocked rotor test on an induction machine aim to estimate magnetization and leakage impedance parameters of induction machine using noload and blocked rotor tests theory an induction machine in its equivalent circuit form is akin to a transformer with slip as an additional parameter. Starting and speed control of 3phase slipring induction. That is why such motors are known as induction motors. How to calculate the slip ring induction motor rotor current. But the rotor construction differs with respect to the type of motor.
Read here to know about the starting arrangement and the role played by the external resistances in obtaining better starting characteristics. As its name indicates stator is a stationary part of induction motor. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Slip ring motors can have many different ratings depending on the duty cycle for which they are specified. Equivalent circuit of an induction motor enables the performance characteristics which are evaluated for steady state conditions. The main difference in a slip ring induction motor is on the rotor construction and usage. Their sole purpose is to allow resistance to be placed in series with.
Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. The synchronous motor gives constant speed whereas induction motors can be started against full load torque. Chapter 3 induction motor and different speed control methods page no 3. In previous articles i have discussed the construction, operation, starting, speed control, and classes of squirrel cage induction motors. It is logical that the least expensive, lowest maintenance type motor.
Ysalient features y robust and nonflammable construction. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. Apr 11, 2017 induction motors generally will have low starting torque compared to dc series motor. The value of slip in induction motor is can never be zero. As the rotor rotates the brushes slip over the rings and provide means of connecting stationary external circuit elements to the rotating windings. Slip ring induction motor working principle electrical mastar. The most severe type of fault was found to be an opencircuited phase of the load such as may occur in a slip ring motor drive when the brushes bounce. It has the advantages of both synchronous motor and induction motor. The slip ring induction motors usually have a phasewound rotor. Slipring induction motor connection and testing youtube.
Squirrel cage induction motor requires significantly less maintenance as it does not contain brushes, commutators, slip rings. Succinctly divided in 14 chapters, the book delves into important concepts of the subject which include armature reaction and commutation. Construction of three phase induction motor electrical4u. Percent slip is a way to measure the speed performance of an induction motor. To start induction motor by rotor resistance starter 8. No load and blocked rotor test on an induction machine. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed. If the standard squirrel cage motor is selected purely on nominal power, for example a 37 kw to replace a 37 kw slip ring motor, then the starting torque may not be sufficient. Since here we are talking about maintenance of induction motor, and it is of two types. An analysis is developed for a doublecage induction motor with any number of cage or end ring faults.
The shortcircuit current of a small 3phase induction motor is 3 times the fullload currents. Rotor induction motor an overview sciencedirect topics. Sometimes 2 additional for shunt field terminals cabinet type and position dc field supply required. Ss 120 x f p 120 x 60 8 900 rpm rotor speed motor slip is known, equation 2.
The squirrel cage induction motor is the most popular type of ac motor. Lecture notes elements of electrical machines 1 veer surendra sai university of technology burla, odisha, india. Regulation of 3phase alternator by zpf and asa methods 9. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine.
Ppt threephase induction motor electrical engineering. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. The slip ring 3phase induction motor is in progress by including resistances, thus the slip ring induction motor s stator winding can be associated in star otherwise delta form. Slip ring motor fundamentals bright hub engineering. A slip ring induction motor can be started with external resistance added in its rotor circuit. Almost 80% of the mechanical power used by industries is provided by three phase induction motors because of its simple and rugged construction, low cost, good operating characteristics, the absence of commutator and good speed regulation. Dec 01, 2017 slipring induction motor also known as rotor resistance start motor. They are especially suitable for heavy load inertia applications.
Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. But there is no restriction for the direction of phase rotation. Apr 30, 2020 ppt threephase induction motor electrical engineering ee notes edurev is made by best teachers of electrical engineering ee. Dec 19, 2017 in this video you will learn connection of slip ring motor with starter panel now you can join our whatsapp group. Slip ring motor conversion to vsd driven standard squirrel. Squirrel cage induction motor slip ring or phase wound induction motor.
Hence slip ring motors are used where one or more of the above requirements are to be met. The singlephase motor stator has a laminated iron core with two windings arranged perpendicularly. Three phase slip ring induction motor my tech info. The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. Slip ring motors electrical calculations and induction. Alternatively, if one is overly slip ring motor conversion to. The slip rings brushes allow external resistors to be connected in series with the winding. Slip ring induction motors slip ring motor starter moflon. Generally we all are know induction motor is most widely used motor in industrial. The rotor winding terminals are connected to three slip rings which turn with the rotor.
Induction motor seminar ppt, pdf report study mafia. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Consider a normal slip ring induction motor having three phase winding on the rotor. Pdf design and analysis of drive system with slip ring. Determine the starting torque as a percentage of fullload torque if fullload slip is 3 per cent. The slip ring or wound rotor motor is an induction machine where the rotor comprises a set of coils that are terminated in sliprings to which external impedances can be connected. Vibrations amplifications on the unsupported shaft extensions of the rotors. Nov 27, 2019 the three phase induction motor is the most widely used electrical motor. A squirrel cage motor is thus preferred to a slip ring motor. Severe arcing between the brushes and collector rings. 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 based on the principle of induction of voltages and currents. Jul 11, 2019 the torque slip curve for an induction motor gives us the information about the variation of torque with the slip. The reason for the name squirrel cage is because of the type of rotor used in these motors. Both common end ring and separate end ring designs are considered. If the ohmic values of these resistances are properly chosen and if the resistors are designed for. Difference between squirrel cage and slip ring induction motor. The slip ring rotor chamber of the ic 411 slip ring induction motor is separated by what is known as a labyrinth seal, which prevents contamination from coal dust. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. 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. This control was derived using rotating frame theory. Also know about the qualities of slip ring induction motors.
The stator is the same as is used with a standard squirrel cage motor. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. A photograph of a wound rotor for an induction machine is shown in fig. Normal induction motors, or squirrel cage type motors, produce a very low starting torque, and for some applications, this low starting torque will cause huge problems.
Please have a look at the below figures of squirrel cage induction and wound rotor slip ring induction motor. The rotor will constantly be turning to align its magnetic field with that of the stator field. The 3phase set of currents, each of equal magnitude and with a phase. The slip ringsbrushes allow external resistors to be connected in series with the winding.
Free download induction motor seminar ppt, pdf report. The figure itself depicts many difference between the two types of motors. Slip ring induction motor are used where high starting torque is required i. Electrical machines ii ee8401, ee6504 anna university. Slip ring induction motors are usually started by connecting starting resistance in the secondary circuit, which are shorted out as the motor speed up. The book principles of electrical machines book by vk mehta and rohit mehta is an ideal text for students who look to gain a current and clear understanding of the subject as all theories and concepts are explained with lucidity and clarity. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. Squirrel cage rotor wound type rotor or slip ring type rotor squirrel cage rotor in this type rotor as the name suggests it is a rotating part of an electrical machine, in which current is induced by transformer action from rotating magnetic field.
The synchronous speed of the motor is given by equation 1. Dont worry, difference between squirrel cage and slip ring type induction motor is tabulated after the figure. In fact, an induction motor can be treated as a rotating transformer i. Y provides smooth and stepless cutting of resistance in rotor circuit of the motor, reducing starting current and increasing starting torque of slipring induction motor. Lecture 6 three phase induction motors cairo university.
Lecture notes institute of aeronautical engineering. Wound rotor with slip rings the rotating magnetic field. 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. The voltage and current is induced in the rotor circuit from the stator circuit for the operation. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. The slip ring motor has very little application in industries. Stator winding can be either star or delta connected depending upon the design. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain.
A power reduction is required for higher ambient temperatures. In an induction motor, torque is equal to the power crossing the air gap divided by the synchronous mechanical speed. When the injected voltage is in phase opposition with the induced rotor e. This article is devoted to slip ring induction motors.
Calculation table for slip ring induction motor used for crane hoisting application calculation table for slip ring induction motor used for crane hoisting application result contain approximate values for crosschecking only inputs power rating p2 100 hp speed n 980 rpm stator voltage e1 415 v stator current is 8 a rotor voltage e2 380 v. Theory and problems of electrical machines, tmh publication, new. No name of experiment page no 1 to perform the brake test on a 3 slip ring induction motor and obtain its performance characteristics 2 to start a 3phase slip ring induction motor by rotor resistance starter. What is the other name for slip ring induction motor. Jul 16, 2018 phase wound induction motor and also slip ring motors. Learn more about the construction and operation of a slip ring induction motor. But how does external resistance aid in better starting characteristics. Feb 20, 2014 terms used in wound rotor slip the difference between a motor s synchronous speed and its speed at full load. Woundrotor motors can be started with low inrush current, by inserting high resistance. The issues related to control techniques with emphasis on induction. 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. Slip ring induction motor working principle electrical. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable.
Wound rotor induction motors with three rotor slip rings have been used in adjustable speed drives for many years. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. Slip ring or phase wound induction motor squirrel cage induction motor construction is complicated due to presence of slip ring and brushes construction is very simple. If the 3phase slip ring induction motor is started as a normal motor with the slip rings shorted, due to low starting torque of slip ring motor, the motor will draw high current i. Stardelta starting of a three phase induction motor 10. Ppt induction motor powerpoint presentation free to. The variation of slip can be obtained with the variation of speed that is when speed varies the. Electrical machines ii question bank download pdf electrical machines ii important questions download pdf.
Table 81 gives typical design letter characteristics for induction motors. Online study material, lecturing notes, assignment, reference, wiki and important questions and answers. Our slip ring induction motors in the 411 cooling class can be overloaded once per hour with 1. What are the applications of a slipring induction motor. Why we need to start induction motor using a starter or with one of starting methods. Most of the application of industrial as well as domestic are this type of induction motor. 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 however, no power is applied to the slip rings. Adjusting the resistance allows control of the speedtorque characteristic of the motor. The torque produced by the induction motor is directly proportional to induction motor slip. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required.
The stator circuit is rated as same in the squirrel cage motor, but the rotor is rated in frame voltage or short circuit current. Construction of squirrel cage induction motor explained. The slip ring rotor chamber has two modification openings. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. The basic idea of an electric motor is to generate two magnetic fields. Jun 06, 2015 starting of slipring motors these motors are practically always started with full line voltage applied across the stator terminals. Wound rotor induction motors ac motors electronics. The motor is connected to the exciter which gives d. A slip ring motor also requires a larger space for the motor and its controls. Slip of induction motor plays an important role in the operation of the induction motor. Torque slip characteristics of induction motor electrical4u.
Speed control of slip ring induction motors part ii. This document is highly rated by electrical engineering ee students and has been viewed 2516 times. An induction motor can be defined as the ac electric motor device in which a power source fed by the alternating current with the help of a primary winding. The rotor terminals are connected to three slip rings which turn. So the main idea behind motor maintenance is to prevent breakdown rather than repairs them.
Portland slip ring induction motorsbrush holder problems and. Design and analysis of drive system with slip ring induction motor for electric traction in india. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. The value of starting current is adjusted by introducing a variable resistance in the rotor circuit. It is logical that the least expensive, lowest maintenance type motor should be used most often.
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