It is very interesting to study the nature of torqueslip characteristics. The slip is defined as the ratio of the difference of synchronous speed and actual. Torque slip characteristics of induction motor full guide. 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. 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. As the induction motor is located from no load to full load, its speed decreases hence slip increases. Torque slip characteristics of 3 phase induction motor. Torque slip characteristic of an induction motor low, medium. We have seen that for a constant supply voltage, e 2 is also constant. Torque slip characteristics of 3 phase induction motor youtube. Torqueslip speed characteristics of induction motor nptel. The equation of the torque is given as shown below. The 3phase set of currents, each of equal magnitude and with a phase. Chapter 3 induction motor and different speed control methods page no 3.
In an induction motor the power transferred to the rotor p d, rotor copper loss p cu2 and mechanical power developed p m are in the ratio of 1. Torque slip characteristics of induction motor electrical4u. Torquespeed characteristics of three phase squirrel cage. Speed torque characteristics of 3 phase induction motor duration.
The motor is mounted in a test rig that allows one to control the torque. Torque slip characteristics of induction motor also known as torquespeed characteristics provide us with the information about the variation of torque with the slip. Induction motor aim to obtain the torquespeed characteristics tn r of a three phase squirrel cage induction motor using 1. This torque is called pull out or break down or stalling torque. Consider a three phase squirrel cage induction motor whose stator has three windings displaced in space by 120. This design exhibits normal torques and fullload slip of approximately 3 percent and can be used for many types of. Three phase induction motor is a particular form of transformer which has secondary winding rotating. The rotor terminals are connected to three slip rings which turn with the. The difference between the synchronous speed ns and the actual speed n of.
When the rotor resistance is increased, so is the slip for maximum torque, and the stable operating slip range of the. This region is called the stable region of operation and operating point of the motor should be in this region. Torque slip characteristics of induction motor your. When the speed varies the slip vary and in contrast the torque will also vary. Threephase induction motor torquespeed characteristics. 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.
Hence the stable operating region of the motor lies for the slip values, s0, and that corresponds to maximum torque. Effect of changing rotor resistance on the torquespeed characteristic of an induction motor. The magnetization current im flowing in the motor s equivalent circuit fig. Torque speed characteristics of induction motor slip. The torque produced by three phase induction motor depends upon the following three factors.
Speed torque characteristics of induction motor from eq. A wound rotor, has a 3phase winding similar to the stator winding. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as absence of brushes. Record all nameplate information for the induction motor. The torque slip characteristic curve is divided roughly into three regions. This means no electromagnetic torque will be produced. Three phase induction motor using written pole technology, main winding, exciter winding, control circuit for optimum utilization. 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, electric motor torque curve torque speed. From the above relation it is seen that, when slip s increases the torque, t also increases. Torque slip characteristic of an induction motor the torque slip characteristic is represented by a rectangular hyperbola. Torqueslip characteristics in three phase induction motor. And the variation of the slip obtained with the variation of speed. The speed of the motor comes to zero, when the slip reaches to 1.
The quantity nsn is sometimes called as slip speed. The rotor winding terminals are connected to three slip rings which turn with the rotor. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Thus, it passes through the point of maximum torque when r 2 sx 20. What are the torqueslip characteristics of a 3phase. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. Theory and analysis of three phase induction motor using. The goerges phenomenon is the operation of a 3phase woundrotor induction motor at half of synchronous speed, and it is obtained by unbalancing the rotor circuit. The basic idea of an electric motor is to generate two magnetic fields. Introduction induction motors are employed in textile mills, agriculture and almost all the manufacturing industries to drive the loads because of its rugged construction and ease operation. The maximum torque developed in an induction motor is called the pull out torque or the breakdown torque. Torqueslip characteristics of three phase induction motor presented by aniket raj 2.
What are the torqueslip characteristics of a 3phase induction motor. One singlephase wattmeter plus miscellaneous apparatus as needed. Hence, no emf will be generated in rotor coils to produce rotor current. Slip torque characteristics of an induction motor my. At low values of slip, torque is approximately proportional to slip s and the torque slip characteristics of induction motor is a straight line. Suad ibrahim shahl 26 equivalent circuit model analysis example a 480v, 60 hz, 6pole, threephase, deltaconnected induction. Torque slip characteristics is the graphical relationship between the torque and slip of an induction machine. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents. For any motor load application, it is imperative to know the torque speed characteristic of the motor. An induction motors rotor can be either wound type or squirrelcage.
The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Themotorisallowedtorunatnoload,andissuppliedwithvarious voltages at nofcmal frequency,rangingfrom 25 percentabove normaltoa value at which the motorwill just continuerunning. The torque will attain a maximum value, at s r 2 x 2. An induction motor can therefore be made without electrical connections to the rotor. Torque equation of three phase induction motor electrical4u. We only have three regions or three cases to illustrate and predict variation and they are. Torque speed characteristic of an induction motor torque speed characteristic is the curve plotted between the torque and the speed of the induction motor. Torque slip characteristics of three phase induction motor the torque slip curve for an induction motor gives us the information about the. It is made up of a number of stampings, which are slotted to receive the windings fig.
Further increases in load on the motor causes, the slip to increase still more. Three phase squire cage induction motor, fully enclosed. Threephase induction 208v motor with matlab revised. Torqueslip characteristics of three phase induction motor dont have big difference than of the main induction motor.
Torque slip characteristics of three phase induction motor. 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. It is logical that the least expensive, lowest maintenance type motor should be used most often. A single phase induction motor is inherently not selfstaring can be shown easily. 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. The rotational speed n of an induction motor, and thus the slip, depends on the operating point, which depends on a load torque requirement so, for a motor, if torque is higher, speed is lower.
The magnetization current im flowing in the motors equivalent circuit fig. 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 slip is defined as the ratio of the difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. The curve obtained by plotting torque against slip from s 1 at start to s 0 at synchronous speed is called torqueslip characteristics of the induction motor.
As we have already discussed the torque of the induction motor in the topic torque equation of an induction motor. This characteristic is very useful for the stability analysis of the machine. Since e1 remains constant with the changes in load, then. Draw and explain the torque slip characteristics of three phase induction motor. Therefore, it very important for induction motor to have a positive value of slip. For the immediate value of the slip, the graph changes from one form to the other. This includes motoring mode, generating mode and braking mode for 0 8. We can derive an equation from the equivalent circuit that allows the calculation of the torque for a given value of slip. To draw the torque slip characteristics of induction motor three phase following points are considered at synchronous speed n s. Although single phase induction motor is more simple in construction and is cheaper than a 3phase induction motor of the same frame size, it is less efficient and it operates at lower power factor. In an induction motor,change in slip from no load to full load is hardly 0. Figure 1 showed a plot of induction motor torque vs speed from zero to synchronous speed. Introduction the squirrelcage induction motor is mounted to the dynamometer. Design a is a generalpurpose design used for industrial motors.
The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. The speed of the induction motor is characterized by the term known as the slip. 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. The stator of an induction motor is, in principle, the same as that of a synchronous motor or generator. A 3 phase induction motor can be used for different applications with various speed and load requirements. The rotor will constantly be turning to align its magnetic field with that of the stator field. Torque slip characteristic of an induction motor low. This curve is called the torquespeed characteristic curve. However, the slip at which the maximum torque occurs changes with rotor resistance.
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