Torque slip characteristics of induction machine electrical. Jun 01, 2018 as we know that, the speed of rotor cannot be equal to synchronous speed i. As in the synchronous motor, applying threephase currents to the armature creates a synchronously rotating magnetic field. Oct 04, 2017 torque speed characteristics of induction motor. The speedtorque characteristic of an induction motor can be modified by effect of voltage variation in induction motor. Nov 18, 2015 induction motor torquespeed characteristics. Derivation of the expression for the gross torque developed as a function of slip speed of induction motor sketch the above characteristics of torqueslip speed, explaining the various features derive the expression of maximum torque and the slip speed at which it occurs.
The terminal box consists of three sets of six terminals of three stator windings. The torque slip characteristic curve is divided roughly into three regions. Design a is a generalpurpose design used for industrial motors. Torque speed characteristics of induction motor electrical.
Slip torque characteristics of an induction motor stable and unstable region of the slip torque characteristics. Two digital multimeters and fluke power quality meter with banana cables from the. The stator copper losses are 2 kw, and the rotor copper losses are 700 w. We only have three regions or three cases to illustrate and predict variation and they are. As the induction motor is located from no load to full load, its speed decreases hence slip increases. The motor operates for the values of the slip between s 0 and s s m. Torque slip characteristics of three phase induction motor the torque slip curve for an induction motor gives us the information about the. Torque slip characteristics of 3 phase induction motor youtube. Themotorisallowedtorunatnoload,andissuppliedwithvarious voltages at nofcmal frequency,rangingfrom 25 percentabove normaltoa value at which the motorwill just continuerunning. Jul 11, 2019 the torque produced by three phase induction motor depends upon the following three factors.
Torque slip characteristics of induction motor your electrical guide. Typical torque speed characteristics of induction motor when supplied from variable voltage at rated frequency are given in fig. If the induction motor s rotor were the rotor bars would be stationary relative turning at synchronous speed to the magnetic field. What is the importance of slip in an induction motor. To measure the inrush current when the motor starts. Ac induction motors are also the most common motors used in main powered home appliances. A 3 phase induction motor can be used for different applications with various speed and load requirements. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol. It follows that any eycient method of speed control must be based on varying the synchronous speed of the weld, rather than the slip. Torque slip characteristics of 3 phase induction motor. F and reactance under running conditions condition for maximum torque under running conditions. Three phase induction motor is a particular form of transformer which has secondary winding rotating.
The quantity nsn is sometimes called as slip speed. The slip for maximum torque is independent of voltage. The two factors that determine the speed of the weld, are the supply. To obtain the load performance characteristics of a three phase squirrelcage induction motor. Hence the stable operating region of the motor lies for the slip values, s0, and that corresponds to maximum torque. The slip is defined as the ratio of the difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Characteristics of a three phase and single phase induction motor. To draw the torque slip characteristics of induction motor three phase following points are considered. The slip is defined as the ratio of difference of synchronous speed and actual rotor. Torque slip characteristics is the graphical relationship between the torque and slip of an induction machine. It is logical that the least expensive, lowest maintenance type motor should be used most often. For induction motor, 0 three phase power supply is connected to the three phase stator winding of induction motor, a rotating magnetic field is produced in the air gap. Firstly the magnitude of rotor current, secondly the flux which interact with the rotor of three phase induction motor and is responsible for producing emf in the rotor part of induction motor, lastly the power factor of rotor of the three phase induction motor. Different types of electrical motors 2 electric motors ac motors synchronous induction squirrel cage slip ring dc motors separately excited self excited series shunt compound 3.
The threephase induction motor is the extensively used for various kinds of industrial drives. Single phase induction motor is very simple and robust in construction. What are the torqueslip characteristics of a 3phase induction motor. The induction motor rotor is a completely shortcircuited conductive cage. The maximum torque developed in an induction motor is called the pull out torque or the breakdown torque. 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. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. We can derive an equation from the equivalent circuit that allows the calculation of the torque for a given value of slip. And on the other hand, when designed to have a high impedance, the motor has an increased amount of torque in a lowspeed range. Torque equation of three phase induction motor electrical4u. However, the slip at which the maximum torque occurs changes with rotor resistance. The stator carries a distributed winding in the slots cut around the inner periphery.
Torque speed characteristic of an induction motor circuit globe. The magnetization current im flowing in the motors equivalent circuit fig. This means that lines of magnetic force must move through conductors in a closed circuit, inducing current in those conductors in order to produce a ma. Slip in electrical induction motors engineering toolbox. Three phase squire cage induction motor, fully enclosed. Assume that a 240v, squirrelcage motor is operated on a 208v, threephase circuit. Torque slip characteristics of three phase induction motor the torque slip curve for an induction motor gives us the information about the variation of torque with the slip.
Torque slip characteristics of induction motor full guide. Torque speed characteristic of an induction motor torque speed characteristic is the curve plotted between the torque and the speed of the induction motor. Load tests on a three phase induction motor and measurement of the inrush current objectives. The number of torque changes based on a given speed of the load. Slip torque characteristics of an induction motor my tech info. To compare the performance of induction motor with d. This includes motoring mode, generating mode and braking mode for 0 of the three modes are. Figure 1 showed a plot of induction motor torque vs speed from zero to synchronous speed. Torque slip characteristics of induction motor electrical4u.
A single phase induction motor requires separate starting circuitry to provide a rotating field to. Torqueslip characteristics of three phase induction motor presented by aniket raj 2. The threephase squirrelcage induction motor can, and many times does, have the same armature stator winding as the threephase synchronous motor. This curve is called the torque speed characteristic curve. Torque slip characteristic of an induction motor the torque slip characteristic is represented by a rectangular hyperbola. Where, s m is the value of the slip corresponding to the maximum torque. Thus, it passes through the point of maximum torque when r 2 sx 20. General principal construction phase wound rotor mathematical proof relation between torque and rotor power factor condition for maximum starting torque rotor e. The speed regulation of the split phase motor is nearly same as that the three phase induction motor therefore it is called as constant speed motor. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors.
Subscribe our electrical engineering related channel electrical academy to get the conceptual videos of network analysis, single phase. Dec 17, 2018 the speed of the induction motor is characterized by the term known as the slip. Torqueslip characteristics of three phase induction motor dont have big difference than of the main induction motor. Pdf speed drive based on torqueslip characteristic of the. The pictorial representation of three phase induction motor with written pole technology is shown in the figure. The scalar control law used for many threephase inductions motor. Record all nameplate information for the induction motor. Calculations show that the slip of the singlephase induction motor is not. Construction, working, torque speed characteristic and application electrical revolution. Slip torque characteristics of an induction motor my.
They are based on the fact that the induction motor torque at a given slip varies as the square of the voltage. When a motor is designed in such a way that impedance of the aluminum conductor of the rotor is reduced, its efficiency is increased in a highspeed range. When the rotor resistance is increased, so is the slip for maximum torque, and the stable operating slip range of the. To draw the torque slip characteristics of induction motor three phase following points are considered at synchronous speed n s. Torque slip characteristics of three phase induction motor presented by aniket raj 2. In an induction motor,change in slip from no load to full load is hardly 0. Torque slip characteristics of induction motor also known as torquespeed characteristics provide us with the information about the variation of torque with the slip. This characteristic is very useful for the stability analysis of the machine.
The friction and windage losses are 600 w, the core losses are 1800 w, and the stray losses are negligible. In twopole singlephase motors, the torque goes to zero at 100% slip zero speed, so these require alterations to the stator such as shadedpoles to provide starting torque. Themotorisallowedtorunatnoload,andissuppliedwithvarious voltages at nofcmal frequency,rangingfrom 25 percentabove normaltoa value at which the motorwill just. Nov 11, 2017 torque slip characteristics of induction machine pull out torque, breakdown torque, motoring mode, generating mode, breaking mode of induction motors, electric motor torque curve torque speed. If the motor slip is known, the rotor speed can be expressed by the equation. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. The slip ringsbrushes allow external resistors to be connected in series with the winding.
Torque slip characteristics of induction machine pull out torque, breakdown torque, motoring mode, generating mode, breaking mode of induction motors. The 3phase set of currents, each of equal magnitude and with a phase. Draw and explain the torque slip characteristics of three phase induction motor. For induction motor, 0 1 slip greater than 1 slip more. Further increases in load on the motor causes, the slip to increase still more.
There are three basic types of small induction motors. Torque slip characteristics in three phase induction motor as the induction motor is located from no load to full load, its speed decreases hence slip increases. Jul 11, 2019 torque slip characteristics of three phase induction motor. The rotor will constantly be turning to align its magnetic field with that of the stator field.
For the immediate value of the slip, the graph changes from one form to the other. Torque slip characteristics of induction motor your. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as. The national electrical manufacturers association nema provides design letters to indicate the torque, slip, and starting characteristics of threephase induction motors they are as follows. Induction motor classification of ac motors induction motor. This includes motoring mode, generating mode and braking mode for. An induction motor is dependent on electromagnetic induction thus the name to produce torque. In the design of the induction motor, operational characteristics can be determined through a series of calculations. This torque is called pull out or break down or stalling torque. A 480v, 60 hz, 50hp, three phase induction motor is drawing 60 a at 0. A wound rotor, has a 3phase winding similar to the stator winding. Torquespeed characteristics of three phase squirrel cage induction motor aim to obtain the torquespeed characteristics tn r of a three phase squirrel cage induction motor using 1. One single phase wattmeter plus miscellaneous apparatus as needed.
At very small slips operating region of the motor and r. As we have already discussed the torque of the induction motor in the topic torque equation of an induction motor. Torque speed characteristics of three phase squirrel cage induction motor aim to obtain the torque speed characteristics tn r of a three phase squirrel cage induction motor using 1. The rotor winding terminals are connected to three slip rings which turn with the rotor. The equation of the torque is given as shown below. Performing these calculations can help the engineer. Torqueslip speed characteristics of induction motor nptel. Characteristics of induction motors nidec corporation. Speed torque characteristics in three phase induction motor.
The torque produced by three phase induction motor depends upon the following three factors. Torqueslip characteristics in three phase induction motor as the induction motor is located from no load to full load, its speed decreases hence slip increases. Apr 21, 2018 torque slip characteristics is the graphical relationship between the torque and slip of an induction machine. More expensive than three phase motors of the same output.
Speed torque characteristics in three phase induction motor uptill now, we have seen torque slip characteristics of an induction motor. The singlephase ac induction motor best fits this description. The basic idea of an electric motor is to generate two magnetic fields. The vector diagram for the split phase induction motor is shown in the figure b. Speed control we have seen that to operate eyciently an induction motor must run with a small slip. Number of poles, frequencies and synchronous induction motor speed. It can be seen from that the figure that for the stable region of operation, the characteristics is similar to that of d. The difference between the synchronous speed ns and the actual speed n of. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Torqueslip characteristics in three phase induction motor. As the winding resistance of starting winding is high, the angle between voltage and current i s is small similarly the inductance of the running or main winding is high therefore the angle between i m and v is very large but less than 90 0 the starting torque in the split phase motor is directly proportional. Threephase induction motor torquespeed characteristics.
The rotor terminals are connected to three slip rings which turn with the. When a motor starts to rotate the slip is 100 % and the motor current is at maximum. By avinash srivastava ravi kumar mtech caid msrit basic induction motor concepts the development of induced torque in an induction motor. And the variation of the slip obtained with the variation of speed. One singlephase wattmeter plus miscellaneous apparatus as needed. This rotating magnetic field sweeps across the rotor conductors and hence an electromagnetic force emf. It is made up of a number of stampings, which are slotted to receive the windings fig. More expensive than threephase motors of the same output. Torque slip characteristic of an induction motor low. The speed of the motor comes to zero, when the slip reaches to 1. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents.
Nov 02, 2019 induction motor, three phase induction motor 1. We can derive an equation from the equivalent circuit that allows the calculation of the torque for a. Torque slip characteristic of an induction motor low, medium. This design exhibits normal torques and fullload slip of approximately 3 percent and can be used for many types of industrial. Torque slip characteristics of three phase induction motor. The magnetization current i m flowing in the motor s equivalent circuit fig. Speed torque characteristics of induction motor from eq. The torque will attain a maximum value, at s r 2 x 2. Firstly the magnitude of rotor current, secondly the flux which interact with the rotor of three phase induction motor and is responsible for producing emf in the rotor part of induction motor, lastly the power factor. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine.
Torque slip characteristics of three phase induction motor youtube. What are the torqueslip characteristics of a 3phase. Due to this, three phase induction motor is practically said to be constant speed motor as drop in speed from no load to full load is not significant. This curve is called the torquespeed characteristic curve. The torque, t of a three phase induction motor is given by. Torquespeed characteristics of three phase squirrel cage.
The value of 208 v is 87% of the rated voltage of the motor. The following example shows that for a given value of slip, the torque varies as the square of the impressed voltage. You should also make a dc measurement of stator winding linetoline resistance. Theory and analysis of three phase induction motor using. But using the relations p m p d ls and n r n s ls we have.
Torque speed characteristics of induction motor slip power. If the rotor speed is less than the synchronous speed n s, the machine acts as a motor. When the speed varies the slip vary and in contrast the torque will also vary. For a typical induction motor, the pullout torque is 2 to 3 times the rated full load torque.
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