Working principle of an induction motor the motor which works on the principle of electromagnetic induction is known as the induction motor. Nov 27, 2019 thus from the working principle of three phase induction motor, it may be observed that the rotor speed should not reach the synchronous speed produced by the stator. Slip ring motors are the motors of choice whenever high starting torque or low starting current are required. Know how to control the speed of slip ring motors bright. This article is devoted to slip ring induction motors. The slip ring induction motor has two distinctly separate parts, one is the stator and other is the rotor. The single phase induction motor resembles, threephase, squirrelcage motor except that, single phase induction motor has no starting torque and some special arrangement have to be made to make it as self starting.
Slip ring induction motor application slip ring induction motor provides high starting torque. But slip ring induction motors over come it by having different speed control methods. Three phase slip ring induction motor my tech info. Ysalient features y robust and nonflammable construction. Contents hide 1 why slip ring induction motor is preferred for high starting torque application. In the ac induction motor, the stator winding generates a rotating magnetic field. The induction motor always runs at speed less than its synchronous speed.
Slip ring motor conversion to vsd driven standard squirrel. The rotor will constantly be turning to align its magnetic field with that of the stator field. The 3phase set of currents, each of equal magnitude and with a phase. There basically 2 types of induction motor depending upon the type. When a threephase power supply is given to the stator of a threephase motor. Principle operation of three phase induction motor the figure shows the portion of a three phase induction motor and is principle explained below. But how does external resistance aid in better starting characteristics. Differentiate between the various types of generating electric power stations. Induction motors have been ruling the industrial world for many decades. A pulsating magnetic field is produced, when the stator winding of the singlephase induction motor shown below is energised by a single phase supply. The most basic ways to control the speed of a slip ring induction motor is either from the stator or rotor side. Induction motor working principle and its equations. The three phase stator winding gets energized when a three phase supply is given to the stator winding, a rotating magnetic field is produced which revolves round the stator its synchronous speed n.
A single phase induction motor has two types of rotor. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. A stator winding is placed in the stator of induction motor and the three phase supply is given to it. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. Working principle of a threephase induction motor rotating. They are especially suitable for heavy load inertia applications. Feb 07, 2018 in this video, i will explain you about the working of the threephase induction motor. Analysis and modelling of an induction machine with a. The slip ringsbrushes allow external resistors to be connected in series with the winding. There are two types of induction motors, one is named as single phase induction motor, while the second one is named as 3 phase 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. Slip ring induction motor fundamentals pnpntransistor.
Substituting the value of s, the maximum value of torque is 2 2 2 0 2 3 1 2 x e x k t s r m. When the injected voltage is in phase opposition with the induced rotor e. When 3phase balanced stator winding is energised from a 3phase balanced supply, a rotation magnetic field is set up which rotates around the stator core at synchronous speed, n s 120fp in rpm. Slip ring induction motor advantages and disadvantages. Due to the lag between the flux current in the rotor. Slip ring induction motor as an extension to the available non slip power recovery mechanisms available for low power srims. 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.
The surfacecooling principle in slip ring induction motors ic 411 the standard threephase slip ring induction motor in protection class ip 55 has ic 411 cooling. Based on the construction of rotor part the 3phase induction motors are divided into two types. This cooling type corresponds to the design of a surfacecooled motor with a housing featuring cooling fins and an external fan mounted on the shaft. Due to this current, a rotating magnetic field of constant amplitude and a constant speed is set up in the air gap between stator and rotor. So, this document provides information about single phase induction motor, constructionstator, rotor, working principle, types of single phase induction motors, starting methods of single phase induction motors, and applications of single. Therefore slip ring induction motors are generally e. Induction motor working principle your electrical guide.
Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. Know about the parameters which are altered to control the speed in slip. This is the basic principle followed by all these types of single phase induction motors. Induction motor is an ac electric motor, having a stator and a rotor just like other motors, but the working principle is a little different which would be discussed further. 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.
Why slip ring induction motor is preferred for high starting torque application. Induction motors generally will have low starting torque compared to dc series motor. Working, application and construction is this article describes construction, working, applications and various problems associated with lim or linear induction motor written by sunil saharan on sunday, july 11th, 2010 at 01. Jan 03, 2018 three phase induction motor operating principle differs from the dc motor in the aspect of current availability in the rotor winding. So obviously the speed of an induction motor can be controlled by varying any of three factors namely supply frequency f, number of pole p or slip s. In a conventional round rotor induction motor the behavior of the machine is only needed to be calculated ov er one pole pi tch.
The result is a flat stator, or upper section, of iron laminations. Ac drives are used to stepless speed control of squirrel cage induction motors mostly used in process plants due to its ruggedness and maintenance free long life. This value of slip is small, for normal wound rotor or slip ring im, without any additional resistance inserted in the rotor circuit. The shape and operation of a linear induction motor can be visualized as depicted in the figure by making a radial cut in a rotating induction machine and flattening it out.
The main methods employed for speed control of induction motors are as follows. The induction motor is made up of the stator, or stationary windings, and the rotor. The basic idea of an electric motor is to generate two magnetic fields. The slip ring induction motors usually have a phasewound rotor. Except some additional functions takes place in this motor which adds an advantage. Induction motors are the most commonly used motors in many applications. Working principle of an induction motor circuit globe. Introduction to induction motor the engineering projects. You also come to know about the law on which the motor works, the types of field induces on the rotor, and. The speed of an induction motor is given as n 120fp 1s. These types of motors are known as selfstarting induction motors. Vibrations amplifications on the unsupported shaft extensions of the rotors.
Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. The induction motor can simply classify as single phase induction motor and three phase induction motor. Working principle of a single phase induction motor circuit. As its name indicates stator is a stationary part of induction motor. Pdf construction of three phase linear induction motor.
Induction machine basics the motor, used in this thesis work, is a two pole induction machine composed of a cage rotor and a stator containing windings connected to the 3phase power supply. Starting of slip ring induction motor explained in an easy. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. What is the operating principle of a 3 phase induction motor. Slip of induction motor plays an important role in the operation of the induction motor. This does not involve the power from on rotor side be fed back to the source. The motor is coupled to a 220 v, separately excited dc generator feeding power to fixed resistance of 10.
These are also called as asynchronous motors, because an induction motor always runs at a speed lower than synchronous speed. The electromagnetic induction is the phenomenon in which the electromotive force induces across the electrical conductor when it is placed in a rotating magnetic field. Portland slip ring induction motorsbrush holder problems and. Squirrel cage induction motor slip ring induction motor 2. Working principle of a single phase induction motor. In the induction motor rotor always rotates speed less than synchronous speed. Possibility of adding additional resistance to control speed. Pdf induction motor with outer rotor and ring stator. Rotor side control of high power slip ring induction motor. In a dc motor, supply is needed to be given for the stator winding as well as the rotor winding. 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. 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 most common type of ac motor being used throughout the work today is the induction motor. Lecture 6 three phase induction motors cairo university.
Slip ring induction motor slip ring induction motor. Starting and speed control of 3phase slipring induction. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. The rotor can be wound a threephase star or delta winding, distributed winding, wound for the same as that of the stator of the motor. An induction motors rotor can be either wound type or squirrelcage type. The value of slip in induction motor is can never be zero. Apr 11, 2017 induction motors generally will have low starting torque compared to dc series motor. The invention of induction motors permanently altered the course of human civilization. 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. Ac drive control speed of ac motor by varying output voltage and frequency through sophisticated microprocessor controlled electronics device. Our 60 minute guide to motor maintenance is designed to give you, the engineer, all the information you need in industrial electric motor maintenance in a format that is concise, easy to understand and is a point of reference. Synchronous speed is the speed of rotation of the magnetic field in a rotary machine, and it depends upon the frequency and number poles of the machine. The rotor of an induction motor can be a squirrel cage rotor or wound. Introduction to induction motor instrumentation and.
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%. 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. Also know about the qualities of slip ring induction motors. In this chapter, we shall focus our attention on the construction, working and characteristics of commonly used singlephase motors. This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. It is logical that the least expensive, lowest maintenance type. Induction motor working principle when a threephase stator winding of an induction motor is connected to the ac supply, current starts flowing in the stator conductors. The rotor terminals are connected to three slip rings which turn with the. The rotating magnetic field produced in the stator will create flux in the rotor, hence causing the rotor to rotate. Once the motor picks up the speed, this additional winding is removed from the supply. 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 working principle of a three phase induction motor is basically lenzs law as explained below. In the case of three phase ac alternating current operation, the most widely used motor is a 3 phase induction motor, as this type of motor does not require an additional starting device. What are the applications of a slipring induction motor. The great majority of medium power industrial motors are of this type. Slip ring induction motor are used where high starting torque is required i. Severe arcing between the brushes and collector rings. 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 motors have the disadvantage over their speed control. Singlephase motors will last for years as well, and usually, most failures from singlephase motors are a result of an inappropriate application rather. The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. An induction motor always operates at a speed lower than the synchronous speed because the rotating magnetic field that occurs in the stator will generate flux in the rotor that will cause the rotor to rotate, but due to the delay of the flow current in the rotor with current flow in the stator, the rotor will never reach its rotating magnetic field speed, that is, the synchronous speed. Principle operation of three phase induction motor my tech info.
A slip ring induction motor can be started with external resistance added in its rotor circuit. But there is no restriction for the direction of phase rotation. This hundredyearold motorinvented by the great scientist nikola teslais the most common motor type. What is slip ring induction motor practical explanation. 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 working principle electrical mastar. The torque produced by the induction motor is directly proportional to induction motor slip. Learn more about the construction and operation of a slip ring induction motor. By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. Working principle of a single phase induction motor a single phase induction motor consists of a single phase winding which is mounted on the stator of the motor and a cage winding placed on the rotor. The remaining two contactors are used to control the speed of a motor by cutting the resistance of rotor of a motor. An induction motor can therefore be made without electrical connections to the rotor.
In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. Applications of single phase induction motor pnpntransistor. The rotor winding terminals are connected to three slip rings which turn with the rotor. The slip ring induction motor working in the induction principle. 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 induction motor slip is usually expressed as a percentage of synchronous. Slip ring induction motor working principle electrical. Induction motor working principle is also similar to the electromagnetic induction principle and induction motor is also known as the rotating transformer. It is in these circumstances that slip ring induction motors are used, as they produce high starting torquefig. The difference being the rotar which has 3 phase wiring in star point or delta connection and also has the sliprings connected to.
A wound rotor, has a 3phase winding similar to the stator winding. Applications of threephase induction motors of size varying from half a kilowatt to. In normal conditions, the slip ring motor functions like a squirrel cage motor. In this type of induction motors, the rotor comes with the separate winding section as similar to stator of the motor. The main induction motor working principle behind these motor are same. This value is higher in the case of squirrel cage im. Electric motor electric motor linear induction motors.
Induction motor with outer rotor and ring stator winding for multispeed applications article pdf available in ieee transactions on energy conversion 284. This is one of the most widely used types of single phase induction motors. Hi friends, in this article i am describing the importance of slip in induction motor and hoping you will find it informative and useful. The stator coil is exactly the same as a 3 phase induction motor. Speed control of slip ring induction motors part ii. C series motors but this disadvantages of the induction motor can be overcome by slip ring induction motor. Rotor side control of high power slip ring induction motor using a single thyristor. List and describe the more commonly used equipment in an electric substation. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. But in an induction motor only the stator winding is fed with an ac supply. The singlephase stator winding produces a magnetic field that pulsates in strength in a sinusoidal manner.
Types of single phase induction motors electronics hub. Adjusting the resistance allows control of the speedtorque characteristic of the motor. If the speeds become equal, there would be no such relative speed, so no emf induced in the rotor, and no current would be flowing, and therefore no torque would be generated. Energy conserving double winding induction motor is ideal to be. Coming to practical world, many industries operate with slip ring induction motor for high starting torque application. An electrical motor is an electromechanical device which converts electrical energy into mechanical energy. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation.
A 3phase, 440 v, 50 hz, 4pole slip ring induction motor is fed from the rotor side through an autotransformer and the stator is connected to a variable resistance as shown in the figure. A pulsating magnetic field is produced, when the stator winding of the singlephase induction motor shown below is energised by a single phase. A linear induction motor provides linear force and motion rather than rotational torque. The first two contactors are used to change the phase sequence of power supply tochange the direction of a motor as per our requirement. 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. Synchronous speed means the speed of the rotating magnetic field in the stator. In common for induction machines is that the stator is made up of a stack of steel laminations pressed into a aluminum or cast iron frame, and. The electromagnetic induction is the phenomenon in which the electromotive force induces across the electrical conductor when it is placed in a.
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