How to control the speed of 3 phase slip ring induction. Speed control of three phase induction motor electrical4u. Wound rotor tecowestinghouse motor company, a world. An843, speed control of 3phase induction motor using. Induction motor by thyristor control on rotor side. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed.
Typical nema design b induction motor speedtorque curve. We can react very quickly due to a comprehensive stock of slip ring motors in a power range up to 15000 kw. 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. Pdf design and analysis of drive system with slip ring. These two stator windings are electrically isolated from each other and are wound for two different numbers of poles. Speed control of slip ring induction motors part ii. A modified rotor chopper for speed control of slip ring induction motors s. Matlabsimulink based design and simulation of speed control. 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.
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 rotor windings are similar to those found on a dc armature, with the coils connected together to a set of rings. The motor can be started using grid rotor resistor. Rotor induction motor an overview sciencedirect topics.
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. In this project we are going to start and control the speed of 3phase slip ring 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. Slip ring induction motor working principle electrical mastar. The starting of an induction motor does not relate to simple switching alone. 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. Stator frequency control as with a cage rotor machine. Advantages and disadvantages of slip ring induction motor. In the slip ring motor, the windings on the rotor are terminated to three insulated slip. 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 wound rotor induction motor using rotor. This work has developed a steadystate and dynamic mathematical model of three phase slip ring induction motors with external impedance. Squirrelcage motors are simpler and cheaper, but harder to control than woundrotor. Adjusting the resistance allows control of the speed torque characteristic of the motor.
The operating point is the intersection of the two characteristics and we can fix for a given load and motor. Speed control of induction motor detailed explanation. Pillai department ofelectrical engineering, indian institute of technology, bombay, powai, bombay 400076, india abstra. 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. Improving motor and drive system performance department of. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17. Pdf rotor side control of high power slip ring induction motor. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. Slip in electrical induction motors engineering toolbox. Slip ring motor characteristics a slip ring motor or a phase wound motor is an induction motor. Where f supply frequency p1 no of poles in slip ring motor p2 no of poles in other motor. This makes constant vf the most common speed control of an induction motor. An induction motor or asynchronous motor is an ac electric motor in which the electric current. Slip ring induction motor fundamentals pnpntransistor.
The speed and power factor of slip ring induction motor can be controlled by injecting slip frequency voltage in. 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. The mechanism employed here is to control the speed. The change in speed depends upon both rotor circuit resistance and load. Starting and speed control of 3phase slipring induction. In speed control by cascading of two induction motors, the rotors of the two motors are mechanically coupled. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. 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. In a current limiting method the closing of contactors at each step is. Experimental results are given and compared with the analytical results. Pdf design and analysis of drive system with slip ring induction.
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. This method is also known as static scherbius drive. A three phase, 50 hz, 4 pole slip ring induction motor has a star connected rotor. Induction motor seminar ppt, pdf report study mafia. Feb 20, 2014 terms used in wound rotor slip the difference between a motor s synchronous speed and its speed at full load. Free download induction motor seminar ppt, pdf report. 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 motors generally will have low starting torque compared to dc series motor. Therefore the efficiency of three phase induction motor is reduced by this method of speed control. Modeling and analysis of slip power recovery controlled.
Three phase slip ring induction motor my tech info. Speed control in three phase induction motor mcqs with answers q1. 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. Induction motors synchronous and full load speed synchronous and full load speed of amplitude current ac induction motors. However, it reduces substantially in a slip ring motor due to the high impedance of the rotor circuit. May, 2017 with the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. Instead of a series of rotor bars, a set of insulated rotor coils is used to accept external impedances. The speed of a pair of slipring motors can be controlled by a cascade connection. This slip speed depends upon the mechanical load on the motor shaft. How to convert a slip ring motor into squirrel cage motor. There are different methods of starting of 3phase slip ring induction motor. Slip ring induction motor working principle electrical. All slip rings are connected with variable resistance. This method is applicable to threephase slip ring induction motor only.
Cascade control speed control of three phase induction. Slip ring motor manufacturer menzel provides shortterm availability and adaptation, applicationspecific requirements and worldwide logistics. Jul 07, 2018 speed control of slip ring induction motor is done by external resistance connected in the rotor side. 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. 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. 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. This topology enables the control of the speed, current, torque and power. The rotor resistance per phase of the winding is 0. Oct 04, 2017 3 phase motor with resistance type starter. 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.
The slip ring motor construction allows the slip ring to control the output of the motor. For both squirrel cage and slip ring induction motor d. Percent slip is a way to measure the speed performance of an induction motor. Starting and speed control of 3phase slip ring induction. The aim behind the development of the project is to limit the current at starting of motor and to develop the high starting torque. 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. The stator construction is the same in both motors. Slip ring induction motor operation motion industries. 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 induction motor 7 ways to control.
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. Because of more advantages, squirrel cage motor is always preferred. With the advent of variablefrequency solidstate power supplies, speed variation can be provided by the more reliable, less expensive squirrelcage motor. Therefore slip ring induction motors are generally employed where load requires high starting torque or good speed control. A slip ring is also used in applications where the load require good speed control. 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. The advantages of the slipring motor are it has susceptibility to speed control by regulating rotor resistance. The main motor m, has slip rings mounted on its shaft from which the e. Combining an inservice motor with a vfd provides facil. 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.
Speed control of induction motor using cycloconverter. Jan 09, 2017 speed control by varying rotor resistance. Refer to appendix c for glossary of technical terms. Using a switching arrangement, at a time, supply is given to one winding only and hence speed control is possible. If the xaxis lies along the line joining the centres of poles rr. If the 3phase slip ring induction motor is started as a normal motor with the slip rings shorted, due to. It also involves its switchgears to control its starting inrush current. Versatile unit will drive virtually any modern 3phase induction motor or any singlephase motor that does not contain a centrifugal switch.
In the same way, the synchronous speed of the differentially cascaded motor can be given by the expression. The slip ring in duction motor has a number of disadvantages compared to squirrel cage motor. The operating point is the intersection of the two characteristics and we can fix for a given load and motor parameters. The speed control is achieved through slip power recovery with the aid of static power devices. An induction motor can therefore be made without electrical connections to the rotor. 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.
The power drawn from the rotor terminals could be spent more usefully. 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. 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. The method which can be used for the speed control of induction motor from stator side is a. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed. One motor is called main motor and the second motor is called auxiliary motor. Apart from using the heat generated in meaning full ways, the slip ring output could be connected to another induction machine. The speed of slipring induction motor can be controlled by. Motor speed control by variable frequency vfd determining motor circuit parameters.
That permits control of the current induced in the armatures, giving variable control of the motor output. Speed control in three phase induction motor mcqs with. This system is basically used for the speed control of large motors of rating more than 4000kw or above. Slip power recovery system for variable speed operation of. The role of cycloconverter in speed control of induction motor is to vary the supply frequency which in turn, changes the speed of motor. An843, speed control of 3phase induction motor using pic18 mcus. 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. The slip ring rotor chamber has two modification openings. 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. Why we need to start induction motor using a starter or with one of starting methods. Squirrel cage induction motors are very widely used in both fixedspeed and.
Chopper controlled slip ring induction motor by international. This type of motor has the advantage of combining winding. Various induction motor speed control methods advantages. Users occasionally inquire as to the feasibility of converting an existing woundrotor moto. A slip ring motor or a phase wound motor is an induction motor which can be started with full. Learn more about the construction and operation of a slip ring induction motor.
A c machines gscheme connect to start and reverse direction of rotation of single phase induction motor. Slip ring motors are invariably started by rotor resistance starting. When looking at the traction perspective, a wound rotor. The slip ring motor has very little application in industries. The torque produced by three phase induction motor is given by, when the rotor is at standstill slip. How to convert a slip ring motor into squirrel cage motor quora. Ac motors which run at fixed speed, without slip, and are generally. 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 slip of the induction motor varies from 5 percent for small motors to 2 percent for large motors. It has susceptibility to speed control by regulating rotor resistance. Speed control of induction motor is possible in two sides. 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. What makes the wound rotor motor a unique induction machine is its rotor. Slip ring induction motor as an extension to the available non slip power recovery mechanisms available for low power srims. As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. 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. A slip ring motor also requires a larger space for the motor and its controls. 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 manual covers squirrel cage rotor motor where. 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.
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 value of slip in induction motor is can never be zero. An 8 pole, 50 hz slip ring induction motor runs at a slip of 2. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Apr 18, 20 starting and speed control of 3phase slip ring induction motor using plc. This article is devoted to slip ring induction motors. Everything youll ever need to know about slip ring motors. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. 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. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. The open circuit voltage on open circuit between the slip rings 0 volts. There is no difference between squirrel cage and slip ring motors. Because the motors operate with a motor speed slower than the synchronous. In the present work, the simulation of speed control of motor at different.
Methods of speed control of induction motor electrical. Speed control of induction motor 7 ways to control induction. The primary winding on the rotor is fed through three slip rings and brushes at line frequency. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. A modified rotor chopper for speed control of slip ring. 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.
What is the working principle of slip ring induction motor. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Slip ring induction motor speed control using a thyristor. Differential equations are solved using computer simulation. Slip energy recovery of an induction motor slip energy recovery is one of the methods of controlling the speed of an induction motor. Speed control of 3phase induction motor using pic18 microcontrollers. Wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. Figure 3 shows the relation between the voltage and. 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. 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. The different methods of speed control of induction motor can be broadly classified in to scalar and vector control methods. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. There are four possible speeds can be obtained by this arrangement.
By adding external resistance to rotor winding starting current will low but it has high starting torque. Slip energy recovery of an induction motor circuit globe. Stator winding can be either star or delta connected depending upon the design. Slip ring motor conversion to vsd driven standard squirrel. By introducing external resistance in the rotor circuit, the speed of the motor can be reduced. In this method of speed control of three phase induction motor, we provide two separate windings in the stator. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process.
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