An induction motor also known as an asynchronous motor is a commonly used ac electric motor. As a result, they often require forced air or watercooling to achieve published specifications. May 31, 2019 a linear induction motor or lim is a special type of induction motor used to achieve rectilinear motion rather than rotational motion as in the case of conventional motors. 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. Characteristics of linear induction motor considering.
The first reports on the end effect of the linear induction motor were made many years ago in connection with the arch motor, an induction motor in which one part of the stator core was removed. Abstract in this study, procedure of lowspeed linear induction motor design and an application of singlesided flat linear induction motor lim have been analysed. Abstract a singlesided linear induction motor with reaction plates is introduced into a doubly fed long stator linear drive railway system in order to solve the switch. Ppt linear induction motor powerpoint presentation. Due to the irregularity and incontinuity of the reaction plate in the switch area, a robust drive con. Linear induction motor dictionary definition linear. The major difference between them is that transformer is static in nature i. The pulsed linear induction motor uses technology developed for the sandia coil gun program for electromagnetic launch.
And because linear induction motors have lower efficiencies, cooling can have a. In the application example, the performance of lowspeed lim whose pole pitch is changed is analysed. If another type of motor was used for the same purpose, being used for that purpose instead of another purpose wouldnt cause it to be called a linear induction motor. In this work, a flux and speed observer for doublesided linear induction motor applications is presented and experimentally validated. It explains what linear induction motors are used for but the definition of a linear induction motor doesnt state that its used for a certian purpose. Mec design and construction of a pulsed linear induction motor. Four basic types of linear induction motor are currently in use. The linear induction motor is similar in construction to a circular motor that has been opened out flat. Abstract a singlesided linear induction motor with reaction plates is introduced into a doubly fed long stator linear drive railway system in order to solve the switch problem and can be also applied in littleused areas of the railway. Considering a cycle of alternating current fig 1 applied to the stator winding we will explain the working of shaded pole motor. An electrical motor is a device that has brought about one of the biggest advancements in the fields of engineering and technology ever since the invention. Linear induction motors are quite an engineering marvel, to convert a general motor for a special purpose with more or less similar working principle, thus enhancing its. So now what was the stator is now a forcer and the rotor becomes a coil or magnet rail.
The electromagnetic induction is the phenomenon in which the electromotive force induces across the electrical conductor when it is placed in a. There are now large numbers of these motors used in practical applications, and the paper describes many of these. This paper explores the construction process of a linear induction motor lim, the basic concepts behind key aspects of linear induction machines construction and the testing process of a working prototype. 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. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. Linear induction motors are less efficient than permanent magnet linear motors, and thus produce more heat for a given continuous force output. In this type of motor, the stator and rotor are called primary and secondary respectively. This is because does not require any starting device i.
Induction motors are the most commonly used motors in many applications. The principle of the three phase linear motor comes to meet the mentioned problems. 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. Electric energy and induction motors the level of prosperity of a community is related to its capability to produce goods and services. How an induction motor works by equations and physics. What is a linear motor principle ironcore motor principle ironless motor principle linear motors are a special class of synchronous brushless servo motors. In a traditional electric motor, the rotor rotating part spins inside the stator static part in a linear motor, the stator is unwrapped and laid out flat and the rotor moves. May 21, 2016 linear brushless dc motor type feature iron core ironless slotless attraction force most none moderate cost medium high lowest force cogging highest none medium power density highest medium medium forcer weight heaviest lightest moderate linear motor type comparison 10 11. It is a special purpose motor that is used for linear motors. Working of shaded pole induction motor the operation of the motor can be understood by referring to the figure which shows one pole of the motor with a shading coil. Design of a single sided linear induction motorslim using a user interactive computer program 32 books linear induction motor 33 patents linear induction motor construction 34 secondary member for singlesided linear induction motor 35 linear induction motor 36. Construction of a pulsed linear induction motor induction launc hers feasible within the scop e of a small undergraduate pro ject.
Ref 1 the seraphim train concept is shown in figure 1. These are also called as asynchronous motors, because an induction motor always runs at a speed lower than synchronous speed. Linear induction motor definition of linear induction. It performs linear motion instead of rotary motion as in a conventional induction motor. A linear induction motor or lim is a special type of induction motor used to achieve rectilinear motion rather than rotational motion as in the case of conventional motors. They work like torque motors, but are opened up and rolled out flat. It is comprised of two parts, the primary and secondary, which interact with one another only when power is. Vivek brahmbhatt already has explained very nicely the construction of lim. A linear motor is effectively an ac induction motor that has been cut open and unwrapped. It can be of two types, single phase induction motor or three phase induction motor. Characteristically, linear induction motors have a finite primary or secondary length, which generates endeffects, whereas a conventional induction motor is arranged. For example, if we consider a dc motor, we will provide a supply to the stator and another to the rotor through a brush arrangement. Squirrel cage wound rotor with slip rings the rotating magnetic field. The pulsed linear induction motor university of edinburgh.
Working principle of an induction motor the motor which works on the principle of electromagnetic induction is known as the induction motor. Principle of lim analysis is similar to that of rim machines a. A parallel history of linear induction motors with applications in linear. Induction motors are the commonest type of motor and account for a very large proportion of heavy duty motors. Pdf construction of three phase linear induction motor. Numerous applications of lims can be found in industry today, one of the most interesting being high speed magnetic levitation railway systems. The definition of a linear induction motor is an electric motor that produces and propels motion in a straight line. Linear induction motors are quite an engineering marvel, to convert a general motor for a special purpose with more or less similar working principle, thus enhancing its versatility of operation.
I would just like to add some practical applications of lim. 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. This is interesting development of a conventional induction motor. Linear induction motor working principle your electrical. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain. Through the electromagnetic interaction between a coil assembly primary part and a permanent magnet assembly. The 3phase set of currents, each of equal magnitude and with a phase. The basic idea of an electric motor is to generate two magnetic fields. Linear brushless dc motor type feature iron core ironless slotless attraction force most none moderate cost medium high lowest force cogging highest none medium power density highest medium medium forcer weight heaviest lightest moderate linear motor type comparison 10 11. Characteristics of linear induction motor considering material of reaction plate change meng li school of electrical engineering, beijing jiaotong university, beijing, china email. Nov 03, 2019 an induction motor also known as an asynchronous motor is a commonly used ac electric motor. There basically 2 types of induction motor depending upon the type. Lets break this down and make it simple, linear induction motor lim theory is most easily understood as a rotary motor that has been cut and unrolled to generate linear motion, instead of rotary motion.
The aim this researc h pro ject is to dev elop a linear induction motor system capable of op erating at 400 v olts with an initial energy of 25 j to in v estigate the lo w feasibilit y op erating concept and erify. Thrust control of traction linear induction motors in switch. The working of the threephase induction motor is based on the principle of electromagnetic induction. This paper explores the construction process of a linear induction motor lim, the basic concepts behind key aspects of linear induction machines construction and the testing process of a working. Numerous papers have been published in the proceedings iee on theoretical aspects of linearinductionmotor design. Furthermore, the constant thrust control in switch areas is analyzed and the future research work is discussed. This video explains how a linear induction motor works. These improvements give a hightraction, compact, and efficient linear motor. What is a linear induction motor and how does it work. To understand the principle of operation let us examine stator of the rotary induction motor fig. Motion and temperature heat control are paramount in energy. But in the induction motor we offer only one supply, so it is really interesting to know how it works.
The force normal to the airgap plane, which has not been quantitatively evaluated or understood before, is found to. Linear motors are electric induction motors that produce motion in a straight line rather than rotational motion. The stator is laid out in the form of a track of flat coils made from aluminum or copper and is known as the primary of a linear motor. How an induction motor works by equations and physics introduction. 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. Linear induction motor lim is an asynchronous motor, working on the same principle an induction motor works, but is designed to produce the rectilinear motion, unlike the rotary movement produced by a motor. A linear induction motor lim is a specific type of alternating current ac, multiplephase machine that provides force and movement in a linear direction.
Traction and normal forces in the linear induction motor. When threephase stator winding of an induction motor is energized from a 3 phase supply, a rotating magnetic field is set up which rotates around the stator at synchronous speed n s. We need to give double excitement to make a machine turn. A linear induction motor provides linear force and motion rather than rotational torque. Linear induction motor is normally referred as linear motor. Before starting to explain how an induction asynchronous generator works, i assume that you know the working principle of an induction motor. But producing goods and services is strongly related to the use of energy in an intelligent way. For singlesided assemblies, the reaction plate consists of 18in. The rotor takes the form of a moving platform known as the secondary. Apr 29, 2018 linear induction motor lim is an asynchronous motor, working on the same principle an induction motor works, but is designed to produce the rectilinear motion, unlike the rotary movement produced by a motor. Introduction linear induction motor lim, is basically an advanced version of motor that is in use to achieve rectilinear motion instead of rotational motion as in ordinary conventional motors. Electric motor electric motor linear induction motors. 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.
Linear induction motor, lowspeed application, linear machine design. The linear induction motor is designed for high speed operation. Oct 23, 2017 choosing a backup generator plus 3 legal house connection options transfer switch and more duration. Just like a dc machine, a same induction machine can be used as an induction motor as well as an induction generator, without any internal modifications. Take a conventional rotary servo motor and unwrap it. While the conventional induction motor gives rotary motion, a working principle of linear induction motor provides translational or linear motion. The simulation of speed control and thrust control is conducted to verify thecontrol syst em. The double sided linear induction motor has primary on both the sides of the secondary. Nov 11, 2011 the linear induction motor is designed for high speed operation. Sizes vary from fractional horsepower to several thousand horsepower used for such appli. There are two basic reasons for the use of singlephase motors rather than 3phase motors. Induction generators are also called as asynchronous generators. The shape and operation of a linear induction motor can be visualized as depicted in the figure by making a radial cut in a.
Linear induction motor having a slotted magnetic field structure wound with a multiphase winding having legs which extend in the slots. If secondary of the linear induction motor is fixed and the primary is free to move, the force will move the primary in the direction of the travelling wave. The magnetic field now sweeps across the flat motor face instead of rotating. Making use of three phase systems, fundamental devices are used to produce. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. Aug 12, 2016 this video demonstrates the working model of using linear induction motor in movement of train. Synchronous speed means the speed of the rotating magnetic field in the stator. Normally lim is used to make a motion frictionless absolutely. With this design, the load is connected directly to the motor. Numerous applications of lim s can be found in industry today, one of the most interesting being high speed magnetic levitation railway systems.
A linear induction motor lim is an alternating current ac, asynchronous linear motor that works by the same general principles as other induction motors but is typically designed to directly produce motion in a straight line. 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. Force engineering ltd how linear induction motors work. The induction motor is made up of the stator, or stationary windings, and the rotor.
Applications of linear induction motors in industry iet. Linear induction motor definition, an electric motor in which a movable part moves in a straight line, with power being supplied by a varying magnetic field set up by a fixed part of the system, as a metal rail on the ground. The thrust produced by a linear induction motor is a factor of the supplied voltage, the amount of slip, and the size of the air gap, as well as the influence of end effects. This is the basic linear induction motor working principle. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Linear motors complement todays linear motion technologies. The lims 3phase coil assembly can be directly connected to the ac line for single speed applications or to an adjustable frequency drive for variable speed control. Like cylindrical induction motor, lim also runs at speed less than synchronous speed. The rotor will constantly be turning to align its magnetic field with that of the stator field. Working principle of an induction motor circuit globe. But the three phase motor has a wider use in industries and homes.
The singlesided stator and the doublesided stator configurations of the infinitely long linear induction motor are analyzed from electromagnetic field theory, and the traction force and the normal force equations are derived using the maxwell magnetic stress tensor. The induced currents interacting with the field produce thrust on rotor plate and drags the rotor plate along within the same direction. However, the direct current homopolar linear motor railgun is another high acceleration linear motor design. Construction of a linear motor or linear induction motor. Basic construction and operating principle like most motors, an ac induction motor has a fixed outer portion, called the stator and a rotor that spins inside with a carefully engineered air gap between. It is comprised of two parts, the primary and secondary, which interact with one another only when power is applied. The double sided linear induction motor dlim is shown in the figure below. The stator generally consists of a multi phase winding in a laminated iron core. In this program, projectiles have been launched electromagnetically to more than 1 ws. More in detail, from a doublesided linear induction motor. To understand its working principle, lets take a look at its structural parts. Linear induction motors can be manufactured in a wide range of force outputs, speeds, and footprints. Linear induction motor a linear induction motor lim is an advanced version of rotary induction motor which gives a linear translational motion instead of the rotational motion. Shaded pole induction motors working and construction.