An887, ac induction motor fundamentals microchip technology. The threephase induction motor is the easiest motor of this type to understand so these notes start with that type. Slots on the internal circumference of the stator house the stator winding. Wound rotor induction motors ac motors electronics. Calculate rotor bar and end ring resistances and hence the conductor losses math and approximations, skin effect coefficients.
Current signature analysis csa is used to accurately measure faults in the induction motor rotors through changes in the rotor magnetic field. The power from the stator winding is transferred to rotor, via air gap by induction principle. The stator separate from rotor by small air gap have ranges from 0. Typically, they consist of 1 a stator with laminations and turns of copper wire and 2 a rotor, constructed of steel laminations with large slots on the periphery, stacked together to form a squirrel cage rotor. 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. Select number of stator slots and suitable three phase winding layout. The most common causes of induction motor failures are due to breaks in rotor bars or shorted circuit rings due to rotor eccentricity. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b. The aim of this research was to study the charactarestics of the. This mechanical energy then can be supplied to various types of loads.
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. 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. Virtually all electrical motors use magnetic field rotation to spin their rotors. Diagnostics of rotor and stator problems in industrial. Analysis and design of ac induction motors with squirrel cage rotors. Speed control at the rotor side we can change the speed at the rotor by,by adding some external resistance in the rotor circuitby cascade connection of the motor. The other differences between the stator and rotor are shown below in the comparison chart. 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. An induction motor or asynchronous motor is an ac electric motor in which the electric current. Record all nameplate information for the induction motor. Speed control of induction motor is possible in two sides.
The greater the misalignment, the greater the induced current and therefore the higher the electromotive force emf and torque generated. The three phase induction motor is the most widely used electrical motor. Noload test, blocked rotor test the equivalent circuit parameters for an induction motor can be determined using specific tests on the motor, just as was done for the transformer. Like any electric motor, a 3phase induction motor has a stator and a rotor. The motors which are all operating under dc supply is called dc motor. Stator and rotor three phase induction motor induction motor transformer ac generator. A rotor also composed of punched laminations, with rotor slots for the rotor winding.
The 3phase set of currents, each of equal magnitude and with a phase. Skin effect causes nonuniform distribution of current in the conductor current density in the rotor bar is higher closer to airgap. Rotor winding monitoring induction motors iris power. Figure shows the disassembled view of an induction motor with squirrel cage rotor. Free download induction motor seminar ppt, pdf report. Determination of the losses in induction machines due to harmonics pdf. The three phase induction motors are simple in construction, rugged, low cost and easy to maintain.
Analysis and control of dual stator winding induction motor. The singlephase induction motor is more subtle and less efficient. The rotor is located inside the stator and is mounted on the ac motors shaft. List and describe the more commonly used equipment in an electric substation. To achieve this, stator windings are arranged around the rotor so that when energised with a polyphase supply they create a rotating magnetic field. We can change the speed at the stator by, changing the supply frequency, changing the supply voltage and changing the number of stator poles. The rotor will constantly be turning to align its magnetic field with that of the stator field. The main difference between slip ring and squirrel cage induction motor is the rotor construction. A threephase induction motor problem enginuity systems. Traditional design of cage rotor induction motors publish.
A stator consisting of a steel frame that supports a hollow, cylindrical core of stacked laminations. Typical induction motor rotors the magnetic field generated in the stator induces an emf in the rotor bars. The basic idea of an electric motor is to generate two magnetic fields. Methods of speed control of induction motor electrical. You should also make a dc measurement of stator winding linetoline resistance using a dmm. 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. In this project, two kinds of induction motor faults, stator short circuit fault and bro ken rotor bar fault, are investigated by using motor current signature analysis mcsa and zero crossing time zct method. Induction motor seminar ppt, pdf report study mafia. The induction motor receives power from the supply mains through the stator windings. The induction motor always runs at speed less than its synchronous speed. An induction motor is an alternating current, rotating asynchronous motor generally consisting of a stationary, primary winding coil or stator and a rotating secondary coilarmature or rotor. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. Current signature analysis is important in tool in preventing.
Induction motor damage curves motor thermal limit curve ieee 620, ieee guide for the presentation of thermal limit curves for squirrel cage induction machines rotor temperature limits during starting stator temperature limits during running. Induction motor output, losses and efficiency my tech info. We saw the construction of the squirrel cage induction 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. The cross sectional view of induction motor and its various parts 4 are as shown in fig 3. The rotor and stator are separated by an air gap which allows free rotation of the rotor. The rotor is separated from the stator by a small airgap which ranges from 0. The objective of these motor components is to make the rotor rotate which in turn will rotate the motor shaft. Rotor induction motor an overview sciencedirect topics. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes however, no power is applied to the slip rings. The induction motor stator resembles the stator of a revolving field, three phase alternator. There are two basic reasons for the use of singlephase motors rather than 3phase motors. Induction motors an induction motor has two magnetically coupled circuits. The rotor then is the rotating part of the ac motor.
Even though thermal and vibration monitoring have been utilized for decades, most of the recent research has been directed toward electrical monitoring of the motor with emphasis on inspecting the stator current of the motor. Its starting torque is somewhat inferior to that of a d. Speed control of induction motor detailed explanation. Synchronous motor speed and slip an interesting characteristic of induction motors is that the actual speed of the rotor always. Ac motor basic stator and rotor operation diagrams. The voltage and current is induced in the rotor circuit from the stator circuit for the operation. Whereas a synchronous motors rotor turns at the same rate as the stator field, an induction motors rotor rotates at a somewhat slower speed than. Abstract electromagnetic forces act between the rotor and stator when the rotor is performing eccentric motions with respect to the stator. An alternating current is supplied to the stator that generates an alternating magnetic field. 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. Modeling and evaluation of stator and rotor faults for induction.
The 3phase set of currents, each of equal magnitude and with a phase difference of 120o, flow in the stator windings and generate a rotating field will constant magnitude. An electric motor is a device which converts an electrical energy into a mechanical energy. Online stator and rotor resistance estimation for induction motors. The significant difference between the rotor and the stator is that the rotor is the rotating part of the motor whereas the stator is the stationary part of the motor. The voltage equations for the stator and the rotor are as given in equations 3. The magnetic field in the air gap from the voltage applied to. The stator losses total 1 kw and the friction and winding losses total 2 kw. Request pdf online stator and rotor resistance estimation for induction motors a ninthorder estimation algorithm is designed which provides online. If the slip of the motor is 4%, find a the mechanical power output b the rotor cu loss per phase and c the efficiency. Finding induction motor parameters locked rotor test finds the rotor parameters r 2, x 2 and stator reactance x 1. In three phase induction motor, the power is transferred from stator to rotor. Pdf modeling of induction motor based on winding function. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below.
The device converts electrical energy to mechanical energy by use of the electromagnetic induction. The mechanical power is obtained at the shaft of the motor to perform mechanical work. As its name indicates stator is a stationary part of induction motor. The rotor bars are not insulated from the rotor core because they are made of metals having less resistance than the.
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 the two. If the induction motor is viewed as a type of transformer, it becomes easy to understand. This rotor is made up from parallel aluminum or copper bars. Noload test balanced voltages are applied to the stator terminals at the rated frequency with the rotor uncoupled from any mechanical load. Equivalent circuit of an induction motor enables the performance characteristics which are evaluated for steady state conditions. Construction of three phase induction motor electrical4u. A three phase induction motor mainly consists of two parts, stator and rotor. Module 6 electromagnetism ac induction motors ac induction motor stator. The power input to a 3phase induction motor is 40 kw. The stator carries a 3phase winding called stator winding while the rotor carries a shortcircuited winding called rotor winding only the stator winding is fed from the 3phase supply. Generally, it is known as the asynchronous motor because its running speed is less than its synchronous speed.
Lecture 6 three phase induction motors cairo university. The motor is mounted in a test rig that allows one to control the torque applied to the motor shaft and to measure both rpm and torque. A 480v, 60 hz, 6pole, threephase, deltaconnected induction motor has the following parameters. The rotating magnetic field produced in the stator will create flux in the rotor, hence. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. Differentiate between the various types of generating electric power stations. In traditional designs of 60 hz linefed induction machines, skin effect is. In turn, a current is produced in the rotor bars and shorting ring and another magnetic field is. How an induction motor works by equations and physics. Construction an induction motor consists essentially of two main parts. This is similar to a transformer, whose secondary is rotating and shortcircuited. An induction motor is based on the principle of induction of voltages and currents.
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