The difference is that, in the case of the induction motor, the secondary windings can move due to the rotation of the rotor the secondary winding of the im, the induced voltage in it does not have the same frequency of the stator the primary voltage 3192014 emdii induction motor design. Adjusting the resistance allows control of the speedtorque characteristic of the motor. The main difference between slip ring induction motor is in rotor construction and usage. Three phase slip ring induction motor my tech info. The life of the motor mostly depends upon the life of the insulating materials since bearings, brush gears, slip rings.
Speed control of wound rotor induction motor using rotor. The operation of the squirrel cage induction motor is similar to transformer having. Percent slip is a way to measure the speed performance of an induction motor. In a conventional round rotor induction motor the behavior of the machine is only needed to be calculated ov er one pole pi tch. Construction of three phase induction motor electrical4u. Crane duty motors, slip ring crane duty motors, squirrel. The rotor will constantly be turning to align its magnetic field with that of the stator field. Air gap provides the space for the rotating magnetic field between the stator and rotor. 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. Oct 04, 2017 3 phase motor with resistance type starter. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. I assume that most slip rings induction motors have a huge coil inside the rotor.
Diff between slip ring and squirrel cage induction motor. Single phase induction motor, theory of operation double. Slip ring induction motor working principle electrical mastar. The construction of slip ring induction motor is quite different compared to other induction motor. A three phase induction motor mainly consists of two parts, stator and rotor. The rotor winding terminals are permanently connected to the slip. The singlephase stator winding produces a magnetic field that pulsates in strength in a. It is mostly used in industrial drives because it is very reasonable and vigorous, economical and reliable. The construction of slip ring induction motor is same as other induction motors. Effectively, the rotor is the secondary winding of a transformer, which is driven by a frequency equal to the slip speed. But electric power is communicated to the rotor by induction. Thyristor, slip ring induction motor srim, stator and rotor. Design and analysis of drive system with slip ring induction motor for. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed.
Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. The torque produced by the induction motor is directly proportional to induction motor slip. The outer periphery of the rotor has a semiclosed slot which carries a 3 phase insulated windings. The squirrel cage induction motor is the most popular type of ac motor.
Pdf design and analysis of drive system with slip ring induction. Dec 22, 2015 its function is to cool down the motor. The basic idea of an electric motor is to generate two magnetic fields. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. Jul 11, 2019 the torque slip curve for an induction motor gives us the information about the variation of torque with the slip. It certainly can rotate at synchronous speed, or even faster. External connections from the brushes are brought out. Torque slip characteristics of induction motor electrical4u. The external resistance can be easily connected through the brushes and slip rings and hence used for speed control and improving the starting torque of three. With the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. Jul 12, 2017 2 rocar arm field armature commutator carbon brush with holder slipring commutator centre fugal swit duration. Vibrations amplifications on the unsupported shaft extensions of the rotors.
In three phase induction motor, the power is transferred from stator to. Users occasionally inquire as to the feasibility of converting an existing woundrotor moto. Operating characteristics of a woundrotor slipring. Compared to squirrel cage rotor the rotor construction is not simple. Improve the speed characteristics of slip ring induction motor by. Feb 20, 2014 terms used in wound rotor slip the difference between a motor s synchronous speed and its speed at full load. Therefore, it is customary to combine them in to a single reactance.
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. Portland slip ring induction motorsbrush holder problems. May, 2017 with the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. Alternatively, if one is overly slip ring motor conversion to. Slip ring motor conversion to vsd driven standard squirrel. 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.
The slip ring rotor chamber has two modification openings. Slip of induction motor plays an important role in the operation of the induction motor. 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. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. The singlephase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner. The main difference in a slip ring induction motor is on the rotor construction and usage. How to convert a slip ring motor into squirrel cage motor quora. Induction motors combine outstanding performance with an advanced longlife. In this article, we shall discuss this motor s construction, working, speed control, advantages, disadvantages, and applications.
Construction of induction motor the three phase induction motor is a preferable type of motor. In the induction motor rotor always rotates speed less than synchronous speed. 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. The frame also contains the stator winding of induction motor. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith slip rings. Pdf construction of three phase linear induction motor. It is also called asynchronous motor because it does not run at a synchronous speed. A single phase induction motor has two types of rotor. 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. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. The variation of slip can be obtained with the variation of speed that is when speed varies the. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place.
If the external controller is set at zero resistance, the motor operates almost exactly the same as the squirrelcage motor, since the rotor is shortcircuited. Slip ring motor fundamentals bright hub engineering. For load sharing to take place automatically, the motor speed should drop considerably as the load increases and this is ensured by using a motor having a high fullload slip, say for example 10%. Home operating characteristics of a woundrotor slipring induction motor fig.
This magnetic field opposes the revolving magnetic field and will combine with the main filed. Pdf the use of squirrel cage motor for traction has revolutionised the motive power. Y provides smooth and stepless cutting of resistance in rotor circuit of the motor, reducing starting current and. When the stator winding of the slip ring motor is connected to the three phase supply, it produces a rotating magnetic field in the same way as a squirrel cage induction motor. The rotor winding terminals are permanently connected to the slip ringsin slip ring type induction motor. The slip is defined as the ratio of difference of synchronous speed and actual rotor. An induction motor sq cage driven by vvvf vfd system is ideal replacement for slipring induction motor. 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. Squirrel cage induction motor vs slip ring induction motor. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals.
The value of slip in induction motor is can never be zero. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Squirrel cage wound rotor with slip rings the rotating magnetic field. Torque slip characteristics of three phase induction motor.
This rings attached with high resistance acts as an external circuit for the rotor. Speed control of wound rotor induction motor using rotor resistance control aim to use variable resistance in the rotor circuit to control wound rotor induction motor speed theory polyphase induction motors are mainly of two types by construction, squirrel cage and woundrotorwith sliprings. Severe arcing between the brushes and collector rings. Pdf rotor side control of high power slip ring induction motor. It is logical that the least expensive, lowest maintenance type. The rotor will constantly be turning to align its magnetic field with the stator field. The slip rings are continuously in contact with the brushes which are pressed against slip rings. Dolivo dobrowolskys first threephase cageinduction motor, 1889, taken from 23. This rotating magnetic field induces voltages in the rotor windings and a rotor current will flow through the closed circuit, formed by the rotor winding, the slip rings, the brushes and the star connected external resistance. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. Starting and speed control of 3phase slipring induction.
Thus, we modify the construction of the present mechanism. However, the torque requirement duty cycle of the crusher motor at various stages is important and the vvvf vfd drive should be able to control the torque. The 3phase set of currents, each of equal magnitude and with a phase. It is a type of motor where its external circuit is connected using some rings.
Cheap copare to slipring im maintainance is easy cost is less compare to slipring im can use at explosive area starting torque is low compare to slip ring im application. A woundrotor motor, also known as slip ringrotor motor, is a type of induction motor where the rotor windings are connected through slip rings to external resistance. Determine the starting torque as a percentage of fullload torque if fullload slip is 3 per cent. In slip ring induction motors the rotor is wound type. The slip power recovery scheme also plays a proactive role as there can be substantial savings of energy in case of a wound rotor induction motor as the slip power recovered can be used to drive. Similarly figure shows the disassembled view of a slip ring motor a stator b rotor c.
The difference between the rotor speed n and the rotating magnetic flux speed n s is called slip. Generally we all are know induction motor is most widely used motor in industrial. The induction motor slip is usually expressed as a percentage of synchronous. Slip in electrical induction motors engineering toolbox. Nov 27, 2019 the three phase induction motor is the most widely used electrical motor. The phase wound rotor is also called as slip ring rotor. The slip ring motor has very little application in industries. Ysalient features y robust and nonflammable construction.
Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. The three ends of three phase windings are permanently connected to these slip rings. The shortcircuit current of a small 3phase induction motor is 3 times the fullload currents. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv.
Slip rings induction motor provides some advantages like provides high starting torque, low starting current and it improves the power factor. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. How to convert a slip ring motor into squirrel cage motor. The most basic ways to control the speed of a slip ring induction motor is either from the stator or rotor side.
The three phase induction motor is the most widely used electrical motor. Most of the application of industrial as well as domestic are this type of 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. Slip ring motors can have many different ratings depending on the duty cycle for which they are specified. The cross sectional view of induction motor and its various parts 4 are as shown in fig 3. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. The slip ring induction motor is shown in the figure below.
Pdf design and analysis of drive system with slip ring. 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. Motor current monitoring and analysis mcsa is a straight forward tool to diagnosing problems with large inductive motors. Jun 01, 2018 slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. They are especially suitable for heavy load inertia applications. An operating and maintenance manual, a terminal plan and. Crompton greaves crane duty motors are designed and manufactured with carefully selected and tested insulating materials to ensure long services. Portland slip ring induction motorsbrush holder problems and. Based on the construction of rotor part the 3phase induction motors are divided into two types. Casue all we would have to do it just add slip rings to the side of the cage. In this section, the construction details of induction motor are discussed.
Stator winding can be either star or delta connected depending upon the design. It is logical that the least expensive, lowest maintenance type motor should be used most often. This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. It consists of a cylindrical core which is laminated.
The construction of a stator is the same for both the squirrel cage and slip ring induction motor. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Hi friends, in this article i am describing the importance of slip in induction motor and hoping you will find it informative and useful. So, it is not advised to start a slip ring induction motor with its rotor terminals. Number of poles, frequencies and synchronous induction motor speed. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination.
We can add external variable resistance to the rotor of this type of motor. Starting of slip ring induction motor explained in an easy. In squirrel cage induction motors the rotor is simplest and most rugged in construction. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Slip ring induction motor fundamentals pnpntransistor. The construction of the present mechanism has been exclusively.
The slip ring induction motors usually have a phasewound rotor. Construction and working of induction motor electrical. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. Slip ring induction motor working principle electrical. In this project we are going to start and control the speed of. To start induction motor by rotor resistance starter 8. Also is it safe to say a squirrel cage induction motor can also be a slip ring at the same time.
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