Nov 27, 2019 the three phase induction motor is the most widely used electrical motor. You should also make a dc measurement of stator winding linetoline resistance using a dmm. By far the most commonly used ac motor is the induction motor. The rotor will constantly be turning to align its magnetic field with that of the stator field. 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. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. Speed control of wound rotor induction motor using rotor. Sep 27, 2016 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. Starting, braking and positioning with threephase cage. Induction motor protection system circuit and its working. The corresponding performance curves are plotted when selecting torquesee generator. Slip energy recovery of an induction motor circuit globe. In the electrical model, the voltage, v, and the slip, s, determine the rotor current.
This paper suggests a novel method of motor starting by. Per phase equivalent circuit of induction motor to determine expressions for torque and power, the equivalent circuit in fig. 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. As with other electrical machines, an equivalent electric circuit can be developed for the purpose of gaining insight into the motors operation. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy. Starting and speed control of 3phase slipring induction. Number of poles, frequencies and synchronous induction motor speed.
For details and the theoretical background of each macro, see the pdf documents in. Advantages of slip ring induction motor it has high starting torque and low starting current. The direction of rotation of a 3 phase induction motor can be reversed by interchanging any two of the three motor supply lines. The absence of slip ring and brushes make the construction of single phase. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Induction motors horizontal and vertical weg electric machinery, wem, induction motors have been specifically designed and manufactured for the most severe industrial applications, such as heavy duty fans, pumps, refiners, compressors, crushers and grinding mill drives. Learn more about the construction and operation of a slip ring induction motor. The induction machine operates between synchronous speed slip 0 and double value of the synchronous speed slip 1. An induction motor or asynchronous motor is an ac electric motor in which the electric current.
In fact, an induction motor can be treated as a rotating transformer i. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. 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. Consult cantoni motors entire general purpose slipring induction motors catalogue on directindustry. 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.
The load test on induction motor is performed to compute its complete performance i. The perphase equivalent circuit of an induction motor is shown in figure 1. It is logical that the least expensive, lowest maintenance type motor should be used most often. When selecting a 3phase induction motor for an application several motor types can fill the need manufactures often specify the motor class best suited to drive the load 3phase induction motors under 500 hp are standardized the frames have standard dimensions a 25 hp, 1725 rpm, 60 hz motor from one manufacture can be. The three phase induction motor is the most widely used electrical motor.
Slip of induction motor plays an important role in the operation of the induction motor. Slip ring induction motor are used where high starting torque is required i. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. April 11, 20 6 of 10 the impedances of the circuits shown in figure 5 are found from noload and blockedrotor tests. Possibility of adding additional resistance to control speed. The motor speed is a function of its rotor resistance. The starting of threephase wound rotor induction motors by stepped resistances added in the rotor circuit suffers from several problems. So, the rotor current is directly proportional to the induced emf. 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. Currentspeed curve of an induction motor it is a vshaped curve having a minimum value at synchronous speed.
Full descriptions of the circuits and the tests are found in reference 1. The torque produced by the induction motor is directly proportional to induction motor slip. There are two major components of an ac induction motor. At another of the lab benches, your instructor has set up the induction motor drive system as shown above. 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. In the rotor resistance control method, the slip power in the rotor circuit is wasted as i 2 r losses during the lowspeed operation. Because it is a capacitortype induction motor, it has a high power factor and runs with a low noise level caution. Figure shows the disassembled view of an induction motor with squirrel cage rotor. Variable frequency induction motor drive schematic. These motors work on 3phase supply and a standard temperature to keep the loads at preferred conditions. General purpose slipring induction motors cantoni motor pdf. The cooling can be integrated so that the induction motor can work in a hermetically sealed environment for instance under water. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i.
This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. The singlephase ac induction motor best fits this description. The value of slip in induction motor is can never be zero. The torquespeed characteristic of an induction motor can be significantly changed by designing. In practice, an ac induction motor is an asynchronous motor in which the rotor lags field speed so its rotor must spin more slowly than the field, or slip. Slip in electrical induction motors engineering toolbox. If the 3phase slip ring induction motor is started as a normal motor with the slip rings shorted, due to low starting torque of slip ring motor, the motor will draw high current i.
Jun 01, 2018 slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. Induction motor introduction an induction motor is an alternating current motor in which the primary winding on one member usually the stator is connected to the power source and a secondary winding or a squirrelcage secondary winding on the other member usually the rotor carries the induced current. This slip must be present, even when operating in a fieldoriented. What is the working principle of slip ring induction motor. How can direction of rotation of 3 phase induction motor. That is why such motors are known as induction motors. Why we need to start induction motor using a starter or with one of starting methods. 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. Record all nameplate information for the induction motor. Lower startup torque higher startup current low r2 n.
The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. Learn more about the construction and operation of a. Lecture 6 three phase induction motors cairo university. As a result of these factors, more than 90 percent of motors installed worldwide are ac induction.
The slip ring induction motor could be used for industrial wires where variable speed and high starting torque are prime requirements. Squirrel cage rotor ac induction motor cutaway view. Let the phase sequence of the threephase voltage applied to the stator winding is. There are two types of induction motors, one with wound type rotor, also called slip ring motor and another one with squirrelcage rotor. Electromagnetic analysis of induction motor using fem 1bhagat komal vipinchandra 2. The page also answers why single phase induction motor is not.
This method is also known as static scherbius drive. Electromagnetic analysis of induction motor using fem. The induction motor is made up of the stator, or stationary windings, and the rotor. Section 5 threephase induction motors by hashem oraee pdf. Motors and drives ac induction motor slip what it is and. The alternating current ac induction motor is one of the most rugged and most widely used machines in industry. Three phase slip ring induction motor my tech info. Connected between the variable frequency drive and the induction motor windings, your instructor will have inserted a power analyzer. This is evident from the equivalent circuit shown in fig. 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.
The induction motor is an essential device in various industrial applications. Induction motor driving a centrifugal compressor advantages. The good power factor of an induction motor can be achieved if the average flux density in the air gap is a absent b small c large d infinity ans. What is common to all the members of this family is that the basic physical process involved in their operation is the conversion of electromagnetic energy to mechanical energy, and vice versa. Introduction to induction motor the engineering projects. The induction motor cannot make a quickreversal run because of the torque acting in the opposite direction. The 3phase set of currents, each of equal magnitude and with a phase. Threephase induction motors with slip ring rotor in the ic 411 cooling class are also designated as ribcooled motors. U, electrical engineering department abstract rotating electrical machines play an important role in the worlds industry. Construction of three phase induction motor electrical4u. Therefore stop the induction motor once, change the wire connections and make a reverse run. The difference, or slip, between actual and synchronous speed varies from about 0. It is logical that the least expensive, lowest maintenance type.
Induction motor introduction an induction motor is an alternating current motor in which the primary winding on one member usually the stator is connected to the power source and a secondary winding or a squirrelcage secondary winding on the other. This work presents a symmetrical v connected twophase induction motor with windings displaced by. Applications of single phase induction motor these are used in low power. Slip, which varies from zero at synchronous speed and 1 when the rotor is at rest. The basic idea of an electric motor is to generate two magnetic fields. Since flux is purposely kept constant, it means that magnetising current is the same at all synchronous speeds. 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. The stator is composed of laminations of highgrade sheet steel. General purpose slipring induction motors product catalogue. Aug 22, 2017 in this video you will learn about slip of induction motor website now you can join our whatsapp group. A wide variety of low speed induction motor options are available to you, such as home appliance, car. The emf induces in the rotor because of the relative motion, or we can say the slip speed of the motor. Sensorless field oriented control of 3phase induction motors.
By putting resistance in series with the rotor windings, the starting current can be kept low while mainta. This article is devoted to slip ring induction motors. The threephase cage induction motor owes its good reputation as a rugged, problemfree drive unit not least to its good starting characteristics. The dissipated heat generated in the motor is output to the motor housing and is discharged by the cooling air of the external fan via the cooling fins. An induction motor can therefore be made without electrical connections to the rotor. Induction motors are popularly used in the industry focus on threephase induction motor main features. As we know, the slip speed is the difference between the synchronous and rotor speed of the induction motor. Induction motors p3 typical torquespeed and powerspeed curves for a 4pole induction motor torque power p these curves are greatly affected by the rotor resistance r2 in our model. Slip energy recovery of an induction motor slip energy recovery is one of the methods of controlling the speed of an induction motor. This minimum is equal to the magnetising current which is needed to create flux in the machine. The induction machine operates between zero speed slip 1 and synchronous speed slip 0. If the motor slip is known, the rotor speed can be expressed by the equation. The circuit impedances are defined in ohms by the following. The induction motor can be made easily and with that the price is rather low compared with other technologies.
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