The induction motor rotates due to the rotating magnetic field in 3 phase induction motor, which is produced by the stator winding in the air gap between in the stator and the rotor. A threephase ac induction motor is the only type where the rotating magnetic field is created naturally in the stator because of the nature of the supply. Working principle of an induction motor circuit globe. By reciting the faust in the park in budapest, he discovered the rotating magnetic field which is the heart of his induction motor and alternating current electricity. Virtually all electrical motors use magnetic field rotation to spin their rotors. Rotating magnetic field in 3 phase induction motor your. Three phase induction motor concept of rotating magnetic. Rotating magnetic field an overview sciencedirect topics. An induction motor is the most modest electrical machine from constructional point of view, in the majority of the cases.
Production of rotating magnetic field studyelectrical. The induction motor is made up of the stator, or stationary windings, and the rotor. Dc motors depend either on mechanical or electronic commutation to create rotating magnetic fields. Magnets have two poles, a north pole and a south pole. A rotating magnetic field, as in the synchronous motor, also forms the basic operating principle of an asynchronous induction motor. It will now be shown that when threephase windings displaced in space by 120 0, are fed by threephase current displaced in time by 120 0. This induces an opposing current in the induction motor s rotor, in effect the motor s secondary winding, when the latter is shortcircuited or closed through an external impedance. Concept of rotating magnetic field electrical concepts. Before we look at how the rotating field is produced, we should be clear what it actually is. Elemental principles an examination of the rudimentary interaction between inductance coils and field magnets will provide some insight into the principles. In an induction motor, when ac supply is given to the the stator, magnetic flux is produced which is revolving at synchronous speed. Whenever the ac supply is connected to the stator windings, line currents i r, i y, and i b start flowing. A threephase ac induction motor is the only type where the rotating magnetic field is created naturally in the stator because of.
Motors, generators, and transformers are similar in that their basic principle of operation involves. Because both the rotor and stator iron surfaces are smooth apart from the regular slotting, and are separated by a small air gap, the flux produced by the stator windings crosses the air gap radially. In these motors, the short circuited turns of the rotor develop eddy currents in the rotating field of the stator which in turn move the rotor by lorentz force. With the use of the rotating magnetic field from the stator, the rotor is able to produce torque. Synchronous and asynchronous developing a rotating magnetic field in stator coil the stator of an ac motor is a hollow cylinder in which coils of insulated wire are inserted. How rotating magnetic field works in ac machines eep.
Elemental principles an examination of the rudimentary interaction between inductance coils and field magnets will provide some insight into the principles behind the rotary magnetic field. The induction motor rotor is a completely shortcircuited conductive cage. Working of three phase induction motor production of rotating magnetic field. The rotating magnetic field is produced by the threephase current of the stator in the actual threephase induction motor. The induction motor stators magnetic field is therefore changing or rotating relative to the rotor. Hope the concept of rotating magnetic field and its production in three phase electrical machine like induction motor is clear.
The rotor body is attached to the shaft in order to transmit the created torque. Understanding the rotating magnetic field by eric p. How is a rotating magnetic field is produced in a three. S l r the flux in the singleturn coil on the rotor surface is. As the rotor conductor is short circuited current flows through them. Induction motor equations engn1931f spring 2017 2 let. Classification of motor rotating magnetic field principle of operation induction motor speed induction motors and transformers disadvantages references here we are giving you induction motor seminar and ppt with pdf report. How a rotating magnetic field is formed in the air gap of a threephase induction motor, when the balanced winding of the stator is fed from a. It can be replaced by permanent magnets in a permanent magnet synchronous motor. This then creates a magnetic field which, through magnetic interaction, links to the rotating magnetic field in the stator which in turn causes the rotor to turn.
In synchronous ac motors, the rotor turns at exactly the same speed as the rotating magnetic field. Direction of rotation the phase current waveforms follow each other in the sequence abc. A rotating magnetic field is a magnetic field that has moving polarities in which its opposite poles rotate about a central point or axis. Pdf version the following animation shows how the rotating magnetic field of a threephase ac induction motor is produced by the interaction of three stator winding sets energized with different. A motor with only armortisseur windings is called an induction motor.
In this animation you get the principle of the rotating magnetic. Using a 60 hz power supply, this process will repeat 60 times per second. Consider a simple electromechanical device consisting of a piece of iron with a copper loop. Classification of motor rotating magnetic field principle of operation induction motor speed induction motors and transformers disadvantages references here we are giving you induction motor seminar. The threephase induction motor is the easiest motor of this type to understand so these notes start with that type. It is also a basis for mri technology, therefore teslas name was honored with the tesla unit, used to measure the capacity of mri machines. Physical layout of induction motor in an induction motor induction refers the field in the rotor is induced by the stator currents and asynchronous refers that the rotor speed is not equal to the stator speed. Induction motors in practice what controls the speed of an ac motor.
Speed is important to the rotating magnetic field of an ac motor. All you need to do is just click on the download link and get it. When a 3phase winding is energized from a 3phase supply, a rotating magnetic field is produced. This video provides basic construction and working principle of three phase induction motor. Nov 20, 2016 this video provides basic construction and working principle of three phase induction motor. When the 3 phase stator windings are fed by 3 phase supply, a magnetic flux of constant magnitude which is rotating at synchronous speed is set up. L r s and be the angular velocities of the magnetic field line frequency, rotor, and slip respectively.
This post will explain you in brief about production of rotating magnetic flux for 2 phase as well as 3 phase supply. The explanation related to the concept of rotating magnetic field rmf in 3phase induction motor im and its visualization is a tricky issue in teachinglearning process. In this period of the current cycle, the rotating field rotates 90o. A magnetic field in a stator can be made to rotate electrically, around and around. In this article, we will try to understand the theory behind the production of rotating magnetic field. Motors, generators, and transformers are similar in that their basic principle of operation involves induction. Working principle of a single phase induction motor production of rotating field. Ac induction motors how ac motors work explain that stuff. Working principle of an induction motor the motor which works on the principle of electromagnetic induction is known as the induction motor. We arrange the threephase winding in such a manner in the slots that they produce one rotating magnetic field when we switch on the threephase ac supply source. The winding wound on the stator of three phase induction motor is also called field winding and when this winding is excited by three phase ac supply it produces a rotating magnetic. Pdf version the following animation shows how the rotating magnetic field of a threephase ac induction motor is produced by the interaction of three stator winding sets energized with different phases a, b, and c of a threephase ac power source.
May 09, 2017 the magnetic rotating field rmf is the basis for the threephase motors whether synchronous or asynchronous induction motors. The rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. If you have any doubt, please write in comment box. When we connect the primary winding, or the stator to a 3 phase ac source, it establishes rotating magnetic field which rotates at the synchronous speed. Elleec cttrriicaall immaacchhiinneess 7ivv t ccooddee. Because both the rotor and stator iron surfaces are smooth. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. After going through this lesson, the students will be able to answer the following questions. Production of rotating magnetic field in polyphase stator. Induction motor basics, single phase and three phase. Production of rotating magnetic field, slip and rotor frequency is also discussed. The threephase windings of the inner stator are spaced 120 electrical degrees apart. Induction motors achieve both these objectives, which is why they now are used in well over 90% of all motor applications. It can be replaced by permanent magnets in a permanent magnet synchronous.
The singlephase induction motor is more subtle and less efficient. The premise for motor operation is that if you can create a rotating magnetic field in the stator of the motor, it. May 15, 2018 in this article, we will try to understand the theory behind the production of rotating magnetic field. An everyday ac induction motor with its case and rotor removed, showing the copper windings of the coils that make up the stator the static, nonmoving part of the motor.
Aug 19, 2018 thus, the rotating magnetic field revolves with a speed of 120fp r. Rotating magnetic fields in threephase ac induction motors. Nov 27, 2019 the stator of three phase induction motor is made up of numbers of slots to construct a 3 phase winding circuit which we connect with 3 phase ac source. For that, we will first imagine one stator of an electric motor where threephase winding is physically distributed in the stator core in such a manner that winding of each phase is separated from other by 120 o in space. Induction motor works on the principle of induction where electro magnetic field is induced into the rotor when rotating magnetic field of stator cuts the. An alternating current is supplied to the stator that generates an alternating magnetic field.
Thus, the description of the rotating magnetic field given thus far applies to both motor and generator action in ac machines. How is a rotating magnetic field is produced in a three phase. Both synchronous and induction types of motors rely on rotating magnetic fields in their stators to cause their rotors to turn. Eddy currents are induced in the rotor conductors by the. The winding wound on the stator of three phase induction motor is. As a voltage and a current is applied to the stator winding terminals, a magnetic field is developed in the windings. In a motor, on the other hand, the rotational motional voltage generated in the armature opposes the applied voltage. Rotating magnetic fields in threephase ac induction. Three phase ac motor theory motors have been described as a transformer with a rotating secondary. It becomes a current carrying conductor in magnetic field and start rotating. This field is such that its poles do no remain in a fixed position on the stator but go on shifting their positions around the stator. Induction motor, rotating magnetic field, threephase balanced winding, and balanced voltage. These coils are designed to produce a rotating magnetic field, which turns the rotor the moving part of the motor in the space between them. Rotating three phase magnetic field figure 1 shows a cross section of an.
Single phase induction motor double revolving field theory the pulsating filed is divided a forward and reverse rotating field motor is started in the direction of forward rotating field this generates small 5% positive slip reverse rotating field generates a larger 1. Lecture 6 three phase induction motors cairo university. The magnetic field in the air gap from the voltage applied to the stator. Ideally, the rotation changes direction at a constant angular rate.
How an induction motor works by equations and physics. The rotor body is the rotating part of the motor and is made of a steel core with aluminium windings. 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. The rotor will constantly be turning to align its magnetic field with that of the stator field. The electromagnetic induction is the phenomenon in which the electromotive force induces across the. Physical layout of induction motor in an induction motor induction refers the field in the rotor is induced by the stator currents and asynchronous refers that the rotor speed is not equal to the stator. The rotor of the squirrel cage three phase induction motor is cylindrical in shape and have slots on its periphery. The motor which works on the principle of electromagnetic induction is known as the induction motor.
Module 6 electromagnetism ac induction motors ac induction motor stator. What is the operating principle of a 3 phase induction motor. Pdf finite element method magnetics based demonstration. The stator of three phase induction motor is made up of numbers of slots to construct a 3 phase winding circuit which we connect with 3 phase ac source. The stator consists of a series of wire windings of very low resistance permanently attached to the motor frame. If we interchange any two of the lines connected to the stator, the new phase sequence will be acb. Jun 02, 2015 these two synchronously rotating magnetic fields, in fact, superimpose on each other and give rise to the actually existing rotating field, which corresponds to the magnetising current of the stator winding. Magnetic fields are an invisible force that attracts ferromagnetic metals such as iron, steel, nickel and cobalt. Because magnets degrade with time, induction motors use shortcircuited rotors instead of a magnet which follow the rotating magnetic field of a multicoiled stator. 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. Induction motor seminar ppt, pdf report study mafia. The stator of the motor consists of overlapping winding offset by an electrical angle of 120 o. Thus revolving field is a key to the operation of the induction motor. However, instead of the rotor being constructed from permanent magnet material, the induction motor has a rotor constructed only from conductive material.
The stator has a three phase stationary winding which can be either star connected or delta connected. Thus, the rotating magnetic field revolves with a speed of 120fp r. These two synchronously rotating magnetic fields, in fact, superimpose on each other and give rise to the actually existing rotating field, which corresponds to the magnetising current of the. Rotating magnetic fields the principle of rotating magnetic fields is the key to the operation of most ac motors. The magnetic rotating field rmf is the basis for the threephase motors whether synchronous or asynchronous induction motors. The production of rotating magnetic field in 3 phase supply is very interesting.
It will now be shown that when threephase windings displaced in space by 120 0, are fed by threephase current displaced in time by 120 0, they produce a resultant magnetic flux which rotates in space as if actual magnetic poles were being rotated mechanically. This post will explain you in brief about production of rotating. Working principle of a single phase induction motor. Both synchronous and induction types of motors rely on rotating magnetic fields in.