Portland slip ring induction motorsbrush holder problems and. Slips rings are connected to the external high resistance circuit. In squirrel cage induction motors the rotor is simplest and most rugged in construction. Cage induction machines institut fur elektrische energiewandlung. Slip ring induction motors slip ring motor starter moflon.
By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. Construction of three phase induction motor electrical4u. Number of poles, frequencies and synchronous induction motor speed. Severe arcing between the brushes and collector rings. What are slip rings and why do some motors use them.
The squirrel cage induction motor is the most popular type of ac motor. In a squirrel cage induction motor, the rotor has conductive bars embedded in slots in the laminations, running the length of the rotor. The load test on induction motor is performed to compute its complete performance i. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. Based on the construction of rotor part the 3phase induction motors are divided into two types. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed.
Home category electrical engineering mcq questions and answers 3 phase induction motors 1 the frequency of the induced emf in an induction motor is a. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Lecture 6 three phase induction motors cairo university. 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. The scheme is somewhat analogous to a primitive kramer system, where a dc motor is coupled to the induction motor shaft and is fed by the rectifier slip power through a diode rectifier. Their sole purpose is to allow resistance to be placed in series with the. This work has developed a steadystate and dynamic mathematical model of three phase slipring induction motors with external impedance. Today, i am going to tell you about a wound rotor induction motor, which is also a type of 3 phase induction motor. Foundation design for high voltage induction motors english pdf leaflet. Maruthi prasad and others published rotor side control of high power slip ring induction motor using a single.
This does not involve the power from on rotor side be fed back to the source. In a dc motor, supply is needed to be given for the stator winding as well as the rotor winding. These are used in increasing the starting torque of the motor. 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. Induction motors the singlephase induction motor is the most frequently used motor in the world most appliances, such as washing machines and refrigerators, use a singlephase induction machine highly reliable and economical figure 1 singlephase induction motor. The mechanism employed here is to control the speed via a single thyristor acting as an onoff switch at the rotor side of this slip ring induction motor. Torque slip characteristics of three phase induction motor. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors.
The stator construction is the same in both motors. But in an induction motor only the stator winding is fed with an ac supply. Pdf three phase slip ring induction motor drive with slip power. Starting and speed control of 3phase slipring induction. A wide variety of low speed induction motor options are available to you, such as home appliance, car. Based on the construction of the rotor, induction motors are broadly classified in two categories. The rotor is the rotating part of the induction motor and is mounted on the shaft of the motor to which any mechanical load can be connected. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. Slipring motors are still used in many branches of industry, and their particular. Slip ring induction motors 5kw slip ring motor motco make slipring induction motors are nearly the same as normal induction motors, except that their rotors are wound with windings. For applications that demand high starting torques, low starting current, or both, baldor is proud to offer abbs broad line of slip ring induction motors. Makwana and others published three phase slip ring induction motor drive with slip power control analysis.
Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. Slip power recovery system for variable speed operation of. Torque slip characteristics of induction motor electrical4u. Starting and 5 control of slipring induction motors contents. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles.
In slip ring induction motors the rotor is wound type. But the rotor construction differs with respect to the type of motor. A power reduction is required for higher ambient temperatures. Adjusting the resistance allows control of the speedtorque characteristic of the motor. Telecommunication engineering, southwest jiaotong university, china, 2005 thesis submitted for the degree of masters of engineering science in school of electrical and electronic engineering the university of adelaide, australia august 2010. Rotor side control of high power slip ring induction motor using a single thyristor. Menzel 3phase slip ring induction motors in protection class ip 55 are designed in the ic 411 cooling class. Wound rotor induction motors chapter ac motors pdf version. Slip ring motor fundamentals bright hub engineering. Free download induction motor seminar ppt, pdf report. Generally, induction motor provides low starting torque as compared to d. So, this motor is used in applications like lifts, pumps, mills where we require high starting torque. As these motors have external resistance connected to its rotor circuit, the value of starting current is adjusted or kept minimum, by increasing the resistance of the rotor circuit. Woundrotor motors can be started with low inrush current, by inserting high resistance into the rotor circuit.
The rotor is normally connected over a 3 stage resistor bank. Threephase squirrelcage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. 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. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. The construction of stator of the induction motor is almost the same as other motors. Squirrel cage induction motor slip ring induction motor 2. The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Higher protection classes can be realized on request at any time. Diagnostics of rotor and stator problems in industrial. Three phase slip ring induction motor my tech info. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Slip ring motors are built using proven standardized motor design, highquality materials and advanced ventilation technology.
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. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Already since 1927, we are a global manufacturer, supplier, and distributor of large slip ring motors up to 15000 kw and,8 kv. In previous articles i have discussed the construction, operation, starting, speed control, and classes of squirrel cage induction motors. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. But how does external resistance aid in better starting characteristics. 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.
Since slip ring induction motors used to accelerate heavy loads over a long period of time and to withstand excessive heat phosphorous bronze slip is used. The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Induction motors generally will have low starting torque compared to dc series motor. Our design experience and application expertise have made us a leading manufacturer of high voltage slip ring.
Squirrelcage rotor almost 90 per cent of induction motors are squirrelcage type, because this type of rotor has the simplest and most rugged construction imaginable and is almost indestructible. The slip rings brushes allow external resistors to be connected in series with the winding. A slip ring is an electromechanical device that allows the transmission of power and electrical signals from a stationary to a rotating structure. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. In the induction motors used in lift and hoists, you will see a type of rotor called a slip ring rotor, whereas in most of the other applications you. A slip ring can be used in any electromechanical system that requires rotation while transmitting power or signals. Fundamental wave model of lineoperated induction machine. Our slip ring induction motors in the 411 cooling class can be overloaded once per hour with 1. An induction motor s rotor can be either wound type or squirrelcage type. Terminals are brought out from each phase for connecting external resistances. 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. There is no electrical connection between these bars.
A wound rotor motor uses three slip rings typically made of copper or a copper alloy mounted to but insulated from the motor shaft. It is in these circumstances that slip ring induction motors are used, as they produce high starting torque fig. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound rotors having three windings each connected in star. Percent slip is a way to measure the speed performance of an induction motor. The value of slip in induction motor is can never be zero. Starter push button type for 23 hp motors 1 machine required. Slip ring induction motor advantages and disadvantages. In this project we are going to start and control the speed of 3phase slip ring induction motor. Therefore slip ring induction motors are generally employed where load requires high starting torque or good speed control. As its name indicates stator is a stationary part of induction motor. Also know about the qualities of slip ring induction motors. Slip ring induction motor working principle electrical mastar. Learn more about the construction and operation of a slip ring induction motor. Speed control of three phase induction motor electrical4u.
What is the difference between a squirrel cage motor and a. In the case of a squirrel cage induction motor, the rotor is inaccessible and rotor circuit resistance is xed, whereas the woundrotor machines are provided with slip rings by which additional resistance can be connected in series with the machine rotor. The addition of these rings along with the external high resistance increases the resistance and decreases the inductive reactance. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. 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 motor seminar ppt, pdf report study mafia. 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. These motors are having the difference in rotor construction. Slip rings a conductive device attached to the end of a wound rotor that conducts current to the brushes. In this article, we will learn about squirrel cage and slip ring induction motors.
The slip ring motor has very little application in industries. General purpose slipring induction motors cantoni motor pdf. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Slip energy recovery of an induction motor circuit globe. Slip ring induction motor fundamentals pnpntransistor. The speed control of induction motor is done at the cost of decrease in efficiency and low electrical power factor. The slip energy recovery method provides the speed control of a slip ring induction motor below its synchronous speed. This article is devoted to slip ring induction motors.
Selecting the correct squirrel cage motor to replace a slip ring motor has been challenging for. It can improve mechanical performance, simplify system operation and eliminate damageprone wires dangling from. This, combined with the fullybraced and vacuumimpregnated windings, ensure they are extremely efficient and reliable. Dec 19, 2017 in this video you will learn connection of slip ring motor with starter panel now you can join our whatsapp group. It is logical that the least expensive, lowest maintenance type motor should be used most often. Singlephase induction motors are used extensively for smaller loads, such as household appliances like fans. Selecting the correct squirrel cage motor to replace a slip ring motor has been challenging for those doing the selection. Oct 04, 2017 how motors work for beginners episode 3. Oct 30, 2015 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 nslip slip speed nsync speed of the magnetic field nm mechanical shaft speed of the motor slip sync mn n n. Wound rotor induction motor applications how it works wound rotor motors are an extremely versatile breed of induction motors. It is explosion proof as there are no slip rings and brushes. The rotor winding terminals are connected to three slip rings which turn with the rotor. These motors are usually started with full line voltage applied across its terminals.
This work has developed a steadystate and dynamic mathematical model of three phase slip ring induction motors with external impedance. Pdf rotor side control of high power slip ring induction motor. Read here to know about the starting arrangement and the role played by the external resistances in obtaining better starting characteristics. The function of a threephase slip ring induction motor is shown in the figure below. The figure below shows the connection and method for recovering the slip energy and power recovery of an induction motor the basic principle of the slip power recovery is to connect an external source of the emf of the slip frequency of the rotor circuit. Slip ring motor conversion to vsd driven standard squirrel. What is the working principle of slip ring induction motor. What are the applications of a slipring induction motor. They are especially suitable for heavy load inertia applications.
In the slip ring motor, the windings on the rotor are terminated to three insulated slip rings mounted on the shaft with brushes resting on them. Features and benefits the slipring motor is an induction machine where the rotor comprises a set of coils that are terminated in slip rings to which external. Slip ring induction motor application slip ring induction motor provides high starting torque. A woundrotor 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. Rotor side control of high power slip ring induction motor. Slip ring induction motor slip ring induction motor. Figure 4 shows the torquespeed characteristics of slip ring induction motor in modified static kramer drive. Stator winding can be either star or delta connected depending upon the design. These bars are shorted at each end with shorting rings. 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.
Abb slipring modular motors abb high voltage induction. Advantages and disadvantages of slip ring induction motor. Slip power recovery system in three phase slip ring. A slip ring induction motor can be started with external resistance added in its rotor circuit. Jul 07, 2018 these motors are usually started with full line voltage.
Squirrel cage induction motor vs slip ring induction motor. Rarely 5% 10% slip ring motors are used in industries because it has several disadvantages like it required. General purpose slipring induction motors product catalogue. The terminals of the rotor windings of the slipring motors. Starting of slip ring induction motor explained in an easy.
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. Pdf three phase slip ring induction motor drive with. Slip in electrical induction motors engineering toolbox. Compared to squirrel cage rotor the rotor construction is not simple. Terms used in wound rotor slip the difference between a motors synchronous speed and its speed at full load. A wound rotor induction motor is also known as slip ring induction motor.
Once the inertia of the load is overcome the rotor is shorted and at that time it is running like an induction motor. Apr 11, 2017 induction motors generally will have low starting torque compared to dc series motor. This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. The catalogue covers slipring induction motors called also wound rotor induction motors that are applied to start a high inertia load or a load that requires a very.
Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. Differential equations are solved using computer simulation. Nov 27, 2019 the three phase induction motor is the most widely used electrical motor. Speed control of wound rotor induction motor using rotor. If the slip ring induction motor is started with all the slip rings or the rotor terminals. Wound rotor induction motors ac motors electronics. Be specially designed for energy saving purpose which is totally enclosed and fancooled type.
In a version of the ac induction motor referred to as a wound rotor motor, slip rings are used not for transferring power, but for inserting resistance into the rotor windings. A 3phase 440 v, 50 hz induction motor has a 4% slip. I will tell about the construction of a wound rotor later in this article. Traditionally, speed control of slip ring induction motor was achieved through varying the rotor resistance. Threephase induction motors are the most common and frequently encountered machines in industry simple design, rugged, lowprice, easy maintenance wide range of power ratings. Rotor side control of high power slip ring induction motor using a. Starting torque of slip ring motor and induction motor with. Vibrations amplifications on the unsupported shaft extensions of the rotors. Dec 19, 2016 slip ring motors are normally used where additional torque is required to overcome the inertia of the load. The generally humidityprotected motor winding is designed to be in thermal class f and is impregnated using the vpi process. Before discussing the methods to control the speed of three phase induction motor one should know the basic formulas of speed and torque of three phase induction. Wound rotor induction motor the engineering projects. A three phase induction motor is basically a constant speed motor so its somewhat difficult to control its speed. The slip ring induction motors usually have a phasewound rotor.
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