How can i find the slip speed of a slip ring induction motor without knowing the rotor speed rated rpm. State the condition for maximum torque of 3phase induction motor. Therefore slip ring induction motors are generally employed where load requires high starting torque or good speed control. Hello, does anyone know the main difference between a slip ring induction motor and a squirrel cage induction motor. But how does external resistance aid in better starting characteristics. The stator of the wrim is directly connected to the grid while the rotor windings are either. The fluxes passes from stator to rotor winding through induction principle. Rotor induction motor an overview sciencedirect topics. Ysalient features y robust and nonflammable construction. Slipring motor manufacturer menzel provides shortterm availability and adaptation, applicationspecific requirements and worldwide logistics. Jul 16, 2018 phase wound induction motor and also slip ring motors. The construction of a stator is the same for both the squirrel cage and slip ring induction motor.
Slip ring induction motor application slip ring induction motor provides high starting torque. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the. Read here to know about the starting arrangement and the role played by the external resistances in obtaining better starting characteristics. There is no difference between squirrel cage and slip ring motors. Jul 11, 2019 torque slip characteristics of three phase induction motor the torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Different self excitation techniques for slip ring self. We can react very quickly due to a comprehensive stock of slip ring motors in a power range up to 15000 kw. Stator winding can be either star or delta connected depending upon the design. 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. Slip and motor current are reduced when the rotor begin turning. Why we need to start induction motor using a starter or with one of starting methods. The rotor winding terminals are connected to three slip rings which turn with the rotor. 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.
Slip ring induction motor fundamentals pnpntransistor. Motor analysis block diagram induction motor starting can be analyzed using electrical, mechanical, and thermal models which interact as diagrammed in figure 1. Also know about the special constructional features of the rotor. A slip ring induction motor can be started with external resistance added in its rotor circuit. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Pdf the use of squirrel cage motor for traction has revolutionised the. The bearing oil ring maintains lubrication when forcefeed oil supply fails, allowing the motor to come safely to a standstill. The slip ring motor has very little application in industries. Diff between slip ring and squirrel cage induction motor. This type of motor has the advantage of combining winding. It is logical that the least expensive, lowest maintenance type motor should be used most often. Slip of induction motor plays an important role in the operation of the induction motor. The summation of all torques acting on the motor shaft comprises the mechanical model.
As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. The rotor has no windings but is made of silicon steel sections, the. The slip ring induction motor working in the induction principle. Publication v, 80% of contribution in the form of theoretical analysis, simula. This is a simple induction motor onlynot a generator. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. The principle of operation of the induction machine. Why should the rotor of a 3phase induction motor not rotate at synchronous speed. Single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of. Good performance, such as high safety, energy saving, compact design, low noise, little vibration, high torque big breakaway torque, reliable operation, stable running and convenient maintenance.
Adjusting the resistance allows control of the speedtorque characteristic of the motor. This is also called absolute slip or fractional slip and is denoted as s. 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. As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. Slip ring motor fundamentals brighthub engineering. Ac motors which run at fixed speed, without slip, and are generally.
Squirrel cage motors have a rotor with short circuited bars whereas slip ring motors have wound rotors having three windings each connected in star. Wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. The slip is defined as the ratio of difference of synchronous speed and actual rotor. Three phase slip ring induction motor my tech info. In the case of a squirrel cage induction motor, the rotor is inaccessible and rotor circuit.
Also know about the qualities of slip ring induction motors. The armature reactance varies from xq to xd periodically. Oct 04, 2017 3 phase motor with resistance type starter. Theseindividualrotormagneticfieldsproducea combine. A theoretical analysis model of induction motor was made based on rotating field theory.
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. 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. Dynamic analysis of cage rotor induction motor using harmonic. Phase wound induction motor and also slip ring motors. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. An ac alternating current induction motor consists of a stator and a rotor and the interaction of the currents flowing in the rotor bars and the rotating magnetic field in the stator generates the torque that turns the motor. The slip of the induction motor varies from 5 percent for small motors to 2 percent for large motors. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. Torque slip characteristics of induction motor electrical4u. Determine the starting torque as a percentage of fullload torque if fullload slip is 3 per cent solution. Slip ring induction motors brush holder problems and solutions nathan schachter. There is no difference between squirrel cage and slip ring.
Slip in electrical induction motors engineering toolbox. Single phase induction motor, theory of operation double. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from movable joints. Advantages and disadvantages of slip ring induction motor. Induction motors combine outstanding performance with an advanced longlife. Induction motor and different speed control methods page no 3. Do you know what happens to slip ring motor when external resistance is added. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit. Advantages of slip ring induction motors the advantages of the wound rotor slip ring induction motors compared with the squirrelcage motors are given below i they have very high starting torque ii they have very low starting current iii they have.
State the steps to draw the equivalent circuit of 3phase induction motor. This work has developed a steadystate and dynamic mathematical model of three phase slip ring induction motors with external impedance. This is a question about squirrelcage induction machine theory. Write the classification of 3phase induction motor. This work has developed a steadystate and dynamic mathematical model of three phase slipring induction motors with external impedance.
Slip ring motor conversion to vsd driven standard squirrel. The torque produced by the induction motor is directly proportional to induction motor slip. 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. Slip ring induction motor working principle electrical mastar. Also does the stator of the induction motor need slip rigns so that the ac current source can be applied to it. When a motor starts to rotate the slip is 100 % and the motor current is at maximum.
Squirrel cage induction motor vs slip ring induction motor. A successful salesman for general electrics motor division once remarked to one of your instructors that, when asked by a customer how a motor. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. So, this motor is used in applications like lifts, pumps, mills where we require high starting torque. If the slip ring induction motor is started with all the slip rings or the rotor. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. Therefore slip ring induction motors are generally employed where load. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. 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. In normal conditions, the slip ring motor functions like a squirrel cage motor. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. 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. Slip ring motor manufacturer menzel provides shortterm availability and adaptation, applicationspecific requirements and worldwide logistics. Inductive reactance depends on the frequency and the slip.
The shortcircuit current of a small 3phase induction motor is 3 times the fullload currents. Similarly figure shows the disassembled view of a slip ring motor a stator b rotor c bearing. Torque slip characteristics of three phase induction motor. Speed control of wound rotor induction motor using rotor. One of the main classifications of asynchronous motors are the slip ring induction motors. To prevent oil vapor ingress into the motor enclosure, the inner side of bearing endshield is provided with additional motor seal. The slip in an induction motor is the difference between the main flux speed and their rotor speed. So slip of the induction motor is defined as the difference between the synchronous speed ns and actual speed of rotor i. This article is devoted to slip ring induction motors. 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. Liquid speed controllers can be supplied to provide required slip resistance to the slip ring motors for speed variation special sized electrolyte tank and heat exchangers are provided to dissipate the heat energy generated in electrolyte during variation of speed. Therefore, it is customary to combine them in to a single reactance.
Be specially designed for energy saving purpose which is totally enclosed and fancooled type. Slip ring induction motor working principle electrical. To analyze the operating and performance characteristics of an induction motor, an equivalent circuit can be drawn. Learn more about the construction and operation of a slip ring induction motor. Thrust fs versus rotor velocity vr of one slim stator unit at a rated slip of 5%, a desired rotor velocity of 15. It is expressed by the percentage of synchronous speed. What is the other name for slip ring induction motor. Portland slip ring induction motorsbrush holder problems and. Slip in electrical induction motors slip is the differentiation between synchronous and asynchronous speed. In the electrical model, the voltage, v, and the slip, s, determine the rotor current.
The bearing oilring maintains lubrication when forcefeed oil supply fails, allowing the motor to come safely to a standstill. 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. Generally, induction motor provides low starting torque as compared to d. Modeling of alternating current motors and reference frame theory. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Also appreciate the external resistances and carbon brush arrangements with the slip rings and advantages of slip ring induction motor. The basic theory and working principles of self excitation in induction machines. Slip ring induction motors are usually started by connecting starting resistance in the secondary circuit, which are shorted out as the motor speed up. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. The woundrotor induction motor or slipring induction motor, as it is. Hence slip ring motors are used where one or more of the above requirements are to be met. Starting and speed control of 3phase slipring induction. The construction of the slip ring induction motor is exactly similar to the construction of squirrel cage induction motor.
This manual covers squirrel cage rotor motor where the rotor consists of a set of non insulated bars that are interconnected by shortcircuiting rings. It certainly can rotate at synchronous speed, or even faster. Pdf design and analysis of drive system with slip ring induction. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. The slip ring rotor chamber has two modification openings. The slip rings brushes allow external resistors to be connected in series with the winding. Be careful it can hurt to tangle with a threephase motor. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. 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. 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. Design of a single sided linear induction motor slim using a user interactive computer program a thesis presented to the faculty of the graduate school university of missouricolumbia in partial fulfillment of the requirements for the degree master of science by sarveswara prasad bhamidi dr.
Differential equations are solved using computer simulation. We will consider a 3phase, y connected machine, the equivalent circuit for the stator is as shown below. Induction motors generally will have low starting torque compared to dc series motor. Starting of slip ring induction motor explained in an easy manner. 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. Wound rotor induction motors with three rotor slip rings have been used in adjustable speed drives for many years. What is the working principle of slip ring induction motor. Portland slip ring induction motorsbrush holder problems. The following section extensively covers the theoretical foundation of induction machines. It is logical that the least expensive, lowest maintenance type. Xd is the synchronous reactance of armature coil offered to the flow of direct axis. Slip rings woundrotor induction motor explain how this motor can be operated as either a synchronous motor or a plain induction motor. Design and analysis of drive system with slip ring induction motor for.
517 640 1514 1109 1502 1073 1257 61 738 1247 133 570 967 574 186 1557 1556 328 1202 424 1401 1173 51 1586 955 966 1402 727 1494 393 455 1230