In the same way, the synchronous speed of the differentially cascaded motor can be given by the expression. In this method of speed control of three phase induction motor, we provide two separate windings in the stator. By the uses of slip ring in an induction motor, we can easily control the speed of induction motor by adding an external resistance to the rotor. The stator construction is the same in both motors. How to convert a slip ring motor into squirrel cage motor quora. Advantages and disadvantages of slip ring induction motor.
Adjusting the resistance allows control of the speed torque characteristic of the motor. Everything youll ever need to know about slip ring motors. Pillai department ofelectrical engineering, indian institute of technology, bombay, powai, bombay 400076, india abstra. The role of cycloconverter in speed control of induction motor is to vary the supply frequency which in turn, changes the speed of motor.
Matlabsimulink based design and simulation of speed control. By introducing external resistance in the rotor circuit, the speed of the motor can be reduced. Improve the speed characteristics of slip ring induction motor by. This system cordinates with the motor during the motor startup and makes it available for process control. Cr this pap er presents the analysisand design of all improvised rotor chopper circuit, which can be used to cont rol the speed of slip ring induction motors. Introduction the technology of slip power recovery controlled by chopper for slip ring induction motor has been widely applied in highvoltage largecapacity motor because of higher power factor, higher efficiency and lower control voltage than those without chopper. The rotor resistance per phase of the winding is 0. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17. This topology enables the control of the speed, current, torque and power. An induction motor can therefore be made without electrical connections to the rotor. If the slip ring induction motor is started with all the slip rings or the rotor. What is the working principle of slip ring induction motor.
Rotor induction motor an overview sciencedirect topics. Slip energy recovery of an induction motor slip energy recovery is one of the methods of controlling the speed of an induction motor. Motor speed control by variable frequency vfd determining motor circuit parameters. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Learn more about the construction and operation of a slip ring induction motor. Slip ring induction motor working principle electrical mastar. Slip ring induction motor operation motion industries. The slip ring in duction motor has a number of disadvantages compared to squirrel cage motor. Modeling and analysis of slip power recovery controlled. Experimental results are given and compared with the analytical results. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. 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. This type of motor has the advantage of combining winding. Starting and speed control of 3phase slip ring induction.
Pdf design and analysis of drive system with slip ring. In this method, a variable starconnected rheostat is connected in the rotor circuit through slip rings and full voltage is applied to the stator winding as shown in fig. Speed control of slip ring induction motors part ii. Squirrel cage induction motors are very widely used in both fixedspeed and. Slip ring motors are invariably started by rotor resistance starting. Pdf rotor side control of high power slip ring induction motor. There are four possible speeds can be obtained by this arrangement. The mechanism employed here is to control the speed. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed. This article is devoted to slip ring induction motors. There is no difference between squirrel cage and slip ring motors. The most basic ways to control the speed of a slip ring induction motor is either from the stator or rotor side.
Stator frequency control as with a cage rotor machine. As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. Speed control of three phase induction motor electrical4u. This method is applicable to threephase slip ring induction motor only. An843, speed control of 3phase induction motor using. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. Because of more advantages, squirrel cage motor is always preferred. Figure 3 shows the relation between the voltage and. So, the speed of induction motor can be changed by changing synchronous speed or by changing the slip of induction motor and then parameter r2 and x2 are changed then torque remain constant and change in slip is affected in speed control.
That permits control of the current induced in the armatures, giving variable control of the motor output. Because the motors operate with a motor speed slower than the synchronous. For both squirrel cage and slip ring induction motor d. A slip ring motor or a phase wound motor is an induction motor which can be started with full. May, 2017 with the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. A modified rotor chopper for speed control of slip ring induction motors s. Versatile unit will drive virtually any modern 3phase induction motor or any singlephase motor that does not contain a centrifugal switch. 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. Slip ring induction motor working principle electrical. Slip ring motor characteristics a slip ring motor or a phase wound motor is an induction motor. The different methods of speed control of induction motor can be broadly classified in to scalar and vector control methods. In a current limiting method the closing of contactors at each step is.
Improving motor and drive system performance department of. Ac motors which run at fixed speed, without slip, and are generally. 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. We can react very quickly due to a comprehensive stock of slip ring motors in a power range up to 15000 kw. One motor is called main motor and the second motor is called auxiliary motor. However, it reduces substantially in a slip ring motor due to the high impedance of the rotor circuit. The speed of slipring induction motor can be controlled by. Design and analysis of drive system with slip ring induction motor for electric traction in india article pdf available in international journal of power electronics and drive systems 53. There are different methods of starting of 3phase slip ring induction motor. The value of slip in induction motor is can never be zero.
Induction motor by thyristor control on rotor side. Rotor side control of high power slip ring induction motor. Slip ring motor manufacturer menzel provides shortterm availability and adaptation, applicationspecific requirements and worldwide logistics. It also involves its switchgears to control its starting inrush current. Free download induction motor seminar ppt, pdf report. These two stator windings are electrically isolated from each other and are wound for two different numbers of poles. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process.
Feb 20, 2014 terms used in wound rotor slip the difference between a motor s synchronous speed and its speed at full load. In the present work, the simulation of speed control of motor at different. Oct 04, 2017 3 phase motor with resistance type starter. The rotor windings are similar to those found on a dc armature, with the coils connected together to a set of rings. The slip ring motors in our mebsgr series that are described in the following text are in the ic 411 cooling class, known as surfacecooled or ribbedcooled. Starting and speed control of 3phase slipring induction.
The slip of the induction motor varies from 5 percent for small motors to 2 percent for large motors. Wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. The terminals of the rotor windings of the slip ring motors are brought out through slip rings which are in contact with stationary brushes as shown in fig. Speed control of 3phase induction motor using pic18 microcontrollers. Speed control in three phase induction motor mcqs with.
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. The advantages of the slipring motor are it has susceptibility to speed control by regulating rotor resistance. The traditional way to control the speed of a wound rotor induction motor is to increase the slip by adding resistance in the rotor circuit. How to convert a slip ring motor into squirrel cage motor. A slip ring motor or a phase wound motor is an induction motor which can be started with full line voltage, applied across its stator terminals. 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. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Induction motor speed so, the im will always run at a speed lower than the synchronous speed the difference between the motor speed and the synchronous speed is called the slip where n slip slip speed n sync speed of the magnetic field n m mechanical shaft speed of the motor n n n slip sync m 3192014.
By adding external resistance to rotor winding starting current will low but it has high starting torque. The slip ring rotor chamber has two modification openings. The slip ring motor construction allows the slip ring to control the output of the motor. In this project we are going to start and control the speed of 3phase slip ring induction motor. A slip ring motor also requires a larger space for the motor and its controls.
A closedloop speed control scheme for a slip ring induction motor is described in this paper. Slip ring induction motors are usually started by connecting starting resistance in the secondary circuit, which are shorted out as the motor speed up. Induction motors generally will have low starting torque compared to dc series motor. Whereas in squirrel cage motor, it is not possible to add any external circuit because the bar of the motor is permanently slotted at the end of the ring.
Slip in electrical induction motors engineering toolbox. Speed control in three phase induction motor mcqs with answers q1. Dec 17, 2019 when the speed control of three phase induction motor is done by adding resistance in rotor circuit, some part of power called, the slip power is lost as i 2 r losses. The torque produced by three phase induction motor is given by, when the rotor is at standstill slip. In this article, we will learn about the speed control of slip ring induction motors and will appreciate that the speed control of slip ring motors are so flexible when compared to the squirrel cage induction motors.
In the slip ring motor, the windings on the rotor are terminated to three insulated slip. The majority of class 4 and specialized cranes around the world operate on an ac supply and are powered by standard ac slip ring motors. Electrical induction motors synchronous speed the speed at which an induction motor operates depends on the input power frequency and the number of electrical magnetic poles in the motor. If the xaxis lies along the line joining the centres of poles rr. Slip ring induction motor fundamentals pnpntransistor. An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. An induction motor or asynchronous motor is an ac electric motor in which the electric current. The speed of a pair of slipring motors can be controlled by a cascade connection. The starter of slip ring induction motor is connected to threephase supply and its rotor is connected to stator of the other machine. Speed control of induction motor 7 ways to control induction.
Slip ring motor conversion to vsd driven standard squirrel. 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. Speed control of induction motor using cycloconverter. This work has developed a steadystate and dynamic mathematical model of three phase slip ring induction motors with external impedance. If the 3phase slip ring induction motor is started as a normal motor with the slip rings shorted, due to.
Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. When you start a 3 phase slip ring induction motor, the poles of the stator create a rotating magnetic field, just as in any induction motor. Induction motor seminar ppt, pdf report study mafia. Apart from using the heat generated in meaning full ways, the slip ring output could be connected to another induction machine. A three phase, 50 hz, 4 pole slip ring induction motor has a star connected rotor. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. All slip rings are connected with variable resistance.
The operating point is the intersection of the two characteristics and we can fix for a given load and motor. Pdf three phase slip ring induction motor drive with. Instead of a series of rotor bars, a set of insulated rotor coils is used to accept external impedances. Speed control of induction motor detailed explanation. Jan 09, 2017 speed control by varying rotor resistance. Typical nema design b induction motor speedtorque curve.
How to control the speed of 3 phase slip ring induction. When looking at the traction perspective, a wound rotor. The change in speed depends upon both rotor circuit resistance and load. A slip ring is also used in applications where the load require good speed control.
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. Jul 07, 2018 speed control of slip ring induction motor is done by external resistance connected in the rotor side. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. Slip energy recovery of an induction motor circuit globe. In speed control by cascading of two induction motors, the rotors of the two motors are mechanically coupled. One of the major difference between the slip ring and the squirrel cage motor is that the slip ring motor has an external resistance circuit for controlling the speed of the motor.
The primary winding on the rotor is fed through three slip rings and brushes at line frequency. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. The speed and power factor of slip ring induction motor can be controlled by injecting slip frequency voltage in. If the ohmic values of these resistances are properly chosen and if the resistors are designed for continuous operation, they can serve dual purpose i. Methods of speed control of induction motor electrical. Therefore the efficiency of three phase induction motor is reduced by this method of speed control. What makes the wound rotor motor a unique induction machine is its rotor. Induction motors synchronous and full load speed synchronous and full load speed of amplitude current ac induction motors. The ac10 thyristor system is a 10 thyrsitor assembly to control both magnitude and polarity of power to the motor, and has a proven track record in the severe industrial environments. Apr 18, 20 starting and speed control of 3phase slip ring induction motor using plc. Combining an inservice motor with a vfd provides facil. A modified rotor chopper for speed control of slip ring.
Slip ring induction motor speed control using a thyristor. A slip ring, three phase induction motor rotates at a speed of 1440rpm, when a supply of 400v, 50hz is applied across the stator terminals. The slip ring motor has very little application in industries. Three phase slip ring induction motor my tech info. The starting of an induction motor does not relate to simple switching alone. A c machines gscheme connect to start and reverse direction of rotation of single phase induction motor. Pdf design and analysis of drive system with slip ring induction. Wound rotor tecowestinghouse motor company, a world. In the rotor resistance control method, the slip power in the rotor circuit is wasted as i 2 r losses during the low speed operation. Percent slip is a way to measure the speed performance of an induction motor. Main motor stator terminal is connected to the supply main and the slip power of main motor is fed to the stator terminals of auxiliary induction motor through slip ring as shown in figure below. This method is also known as static scherbius drive. An843, speed control of 3phase induction motor using pic18 mcus. The open circuit voltage on open circuit between the slip rings 0 volts.
Stator winding can be either star or delta connected depending upon the design. Speed control of induction motor 7 ways to control. Users occasionally inquire as to the feasibility of converting an existing woundrotor moto. Speed control of wound rotor induction motor using rotor. Chopper controlled slip ring induction motor by international. The power drawn from the rotor terminals could be spent more usefully. The aim behind the development of the project is to limit the current at starting of motor and to develop the high starting torque. The main motor m, has slip rings mounted on its shaft from which the e. This manual covers squirrel cage rotor motor where. Refer to appendix c for glossary of technical terms.
An 8 pole, 50 hz slip ring induction motor runs at a slip of 2. Why we need to start induction motor using a starter or with one of starting methods. Slip power recovery system for variable speed operation of. The speed control is achieved through slip power recovery with the aid of static power devices.
Speed control of induction motor is possible in two sides. Where, f frequency and p is the number of poles the speed of induction motor is given by, where, n is the speed of the rotor of an induction motor, n s is the synchronous speed, s is the slip. This slip speed depends upon the mechanical load on the motor shaft. Differential equations are solved using computer simulation. 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. Cascade control speed control of three phase induction. This makes constant vf the most common speed control of an induction motor.
The rotor resistance and stand still reactance per phase are 0. The speed of a threephase induction motor driving a given load is determined by matching the torque speed characteristics of the motor and load, as shown in fig. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. Using a switching arrangement, at a time, supply is given to one winding only and hence speed control is possible. Squirrelcage motors are simpler and cheaper, but harder to control than woundrotor. It has susceptibility to speed control by regulating rotor resistance. The operating point is the intersection of the two characteristics and we can fix for a given load and motor parameters. Where f supply frequency p1 no of poles in slip ring motor p2 no of poles in other motor. Slip ring motor conversion to vsd driven standard squirrel cage ac motor by j van niekerk, zest weg group over a number of years slip ring motors have largely been replaced by standard squirrel cage ac induction motors, often in conjunction with ac variable speed drives vsds. With the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. Makwana and others published three phase slip ring induction motor drive with slip power control analysis for different load torque using microsoft excel as software. This system is basically used for the speed control of large motors of rating more than 4000kw or above.
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