Microsoft powerpoint ieee sf motor protection fundamentals. Torque slip characteristics of induction motor also known as torquespeed characteristics provide us with the information about the variation of torque with the slip. At synchronous speed, no torque is produced by the motor. Torque slip characteristics of induction motor electrical4u. Speedtorquestarting characteristics variations in the voltage will l1ave a significant impact on the motor starting torque since it will vary as the square ofthe flux density. For the immediate value of the slip, the graph changes from one form to the other. The slip for maximum torque is independent of voltage.
Torque slip characteristics of induction motor your. A matlab mfile to calculate and plot the two torquespeed characteristics is shown. With the singlephase motor, the starting torque is generally smaller than the operating torque, while the threephase motor features a relatively greater starting torque. The speed of the motor comes to zero, when the slip reaches to 1. Torquespeed characteristics of three phase squirrel cage induction motor aim to obtain the torquespeed characteristics tnr of a three phase squirrel cage induction motor using 1. This includes motoring mode, generating mode and braking mode for. The magnetization current i m flowing in the motor s equivalent circuit fig. In addition, we clearly need to know what perform ance is required. For motor speeds below the nominal value, the torque capacity of the motor is preserved with the proposed relationship. The basic idea of an electric motor is to generate two magnetic fields. An induction motor is normally sized for the anticipated full load torque. Torque equation of three phase induction motor electrical4u. A torquespeed characteristic curve combining highresistance effects at low.
Induction motor torque speed curveinduction motor torque speed characteristics the torque slip curve for an induction motor gives us the information about the variation of torque with the slip. In modern induction motors, the most common type of rotor has castaluminum conductors and shortcircuiting end rings. Torquespeed characteristics 3192014 typical torquespeed characteristics of induction motoremd ii induction motor design viii sem electrical. Torquespeed characteristics of squirrel cage induction motor. Pdf this paper presents a competent approach to explain torquespeed, torque time and speedtime characteristic of an induction motor. Slip torque characteristics of an induction motor my. The load torque is characterized by an initial breakaway torque value, l, and momentary decrease followed by the increase to its final value, f. When the speed varies the slip vary and in contrast the torque will also vary. Typical torque speed characteristics of induction motor when supplied from variable voltage at rated frequency are given in fig. The speed torque curves of induction motors are usually determined from a set of their.
Recalling that the equivalent circuit is the perphase representation of the machine, the current drawn by the circuit is given by. If the rotor speed is less than the synchronous speed n s, the machine acts as a motor. Typical torquespeed curve of a squirrelcage induction motor given in figure 1 provides information. Maximum torquespeed characteristics in motor and generator operation modes the circle diagram and corresponding torquespeed character. Induction motor aim to obtain the torquespeed characteristics tn r of a three phase squirrel cage induction motor using 1. Torque speed characteristic of an induction motor torque speed characteristic is the curve plotted between the torque and the speed of the induction motor. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as. Speed control of three phase squirrel cage induction motor. The number of torque changes based on a given speed of the load. Induction motor torque speed characteristics all about. The speedtorque curves of induction motors are usually determined from a set of their. The 3phase set of currents, each of equal magnitude and with a phase.
At one extreme, for example, in a steelrolling mill, it may be necessary. To draw the torque slip characteristics of induction motor three phase following points are considered at synchronous speed n s. E 1 we know that transformation ratio k is defined as the ratio of secondary voltage rotor voltage to that of primary voltage stator. The splitphase motor is also known as an induction startinduction run motor.
Torque slip characteristics of induction machine pull out torque, breakdown torque, motoring mode, generating mode, breaking mode of induction motors. The induction machine operates between zero speed slip 1 and synchronous speed slip 0. Torque slip characteristic of an induction motor the torque slip characteristic is represented by a rectangular hyperbola. 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. The maximum torque developed in an induction motor is called the pull out torque or the breakdown torque. Pdf uniqueness of torquespeed characteristics of an induction. The slip is defined as the ratio of difference of synchronous speed and actual rotor. When the speed varies the slip vary and in contrast the torque will also var y. Induction motor speed torque characteristics typically, when a nema design b induction motor is started acrosstheline, an inrush current of 600 to 800% fla occurs, corresponding to the starting torque point. Torque and horsepower torque is the turning effort or force acting through some. As we have already discussed the torque of the induction motor in the topic torque equation of an induction motor. Drive mode use in conjunction with performance testtorquespeed characteristics motor. The implementation is done using a rectifier and an inverter, where the pwm triggering pulses were generated by using pic micro controller for switching the igbts of the inverter. Load torque will depend on the type of load be it a pump or fan etc.
As the load is accelerated to the fullload torque point, the current decreases to 100% fullload current at 100% fullload torque. Where, t is the torque produced by the induction motor. The torque developed by an asynchronous induction motor varies when the motor accelerates from zero to maximum operating speed. The corresponding performance curves are plotted when selecting torquesee. The slip is defined as the ratio of difference of synchronous speed and actual rotor speed to the synchronous speed of the machine. Typically, an electric motor has at three rated torques. Torque speed characteristics of induction motor slip. Pdf this letter states and proves a uniqueness theorem for the torquespeed characteristics tsc of an induction motor. This file calculates the equivalent circuit of a three phase induction motor from the data of open circuit test and blocked rotor test. However different motor designs will affect the shape of the curve and the locked rotor current. This characteristic is very useful for the stability analysis of the machine. The speedtorque characteristic of an induction motor can be modified by effect of voltage variation in induction motor. They are based on the fact that the induction motor torque at a given slip varies as the square of the voltage. The maximum torque that the motor can produce is called the breakdown torque.
Analytical approach to determine speedtorque curve of induction. Torque slip characteristics of three phase induction motor. The locked rotor torque or starting torque is the torque an electrical motor develops when starting at zero speed. Characteristics of induction motors nidec corporation. Induction motors are widely used every production process today. 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. Application report induction motor speed torque characteristics. Starting of 3 phase induction motors, high starting torque motors, speed control, rheostatic method, pole changing method, cascade control of speed, double cage induction motor, cogging an d crawling of induction motor. The impactthatvoltage variations have on ac induction. Hence the stable operating region of the motor lies for the slip values, s0, and that corresponds to maximum torque. Load requirements torquespeed characteristics the most important things we need to know about the load are the steadystate torquespeed characteristic, and the effective inertia as seen by the motor.
The rotor will constantly be turning to align its magnetic field with that of the stator field. A high starting torque is more important for application or machines. The magnetization current im flowing in the motors equivalent circuit fig. The speed at which the magnetic field rotates is the synchronous speed of the motor and is determined by the number. Torquespeed characteristic of induction motor in order to estimate the speed torque characteristic let us suppose that a sinusoidal voltage is impressed on the machine.
Torque slip characteristics of induction motor full guide. To obtain the torquespeed characteristics tnr of a three phase squirrel cage induction motor using. Simulink model of three phase induction motor file. Torque slip characteristics is the graphical relationship between the torque and slip of an induction machine. Lecture 6 three phase induction motors cairo university. Create scripts with code, output, and formatted text in a single executable document. Communities more files in the power electronics control community.
Torquespeed characteristics of three phase squirrel cage induction motor aim. Determination of the torquespeed characteristic of. The motor cannot operate in the steadystate at speeds below the breakdown torque. Doc describes basic principles of ac motor operation pertinent to use with vfds. Torquespeed characteristics of motors 17 4 ac motors 19 a. Pdf performance characteristics of induction motor under. Induction motor the starting torque is low, typically 100% to 175% of. Generally, this, where 100% is equal to synchronous speed, as determined by the mains frequency and number of pole pairs. Single phase induction motor double revolving field theory the threephase induction motor starting torque inversely depends on the slip this implies that a small positive slip 0. Ninformation from the motor manufacturer includes a speed torque curve plotted in percent of full load torque and percent of synchronous speed, full load torque, full load speed, wk2 of the motor rotor, and an amps vs. And the variation of the slip obtained with the variation of speed. The only part of the curve, which is almost linear, is good for operation. Torquespeed characteristics of three phase squirrel cage. It also calculates the thevenin equivalent circuit parameters, maximum torque induced, starting torque and slip for maximum power or torque.
Speed control of three phase squirrel cage induction motor using vf method is implemented. Thus, it passes through the point of maximum torque when r 2 sx 20. Pdf estimating torquespeed characteristic of threephase. The torque the motor produces changes proportionally to roughly.
Threephase induction motor torquespeed characteristics. Equivalent circuit of an induction motor and torque speed. From above equation greater the slip greater will be the induced e. Speed of an induction motor the magnetic field created in the stator rotates at a synchronous speed n s. A new v f relation that improves the speed response of the single squirrel cage induction motor is presented and is defined by a frequency factor. Figure 7 induction motor torquespeed characteristic. Sometimes this characteristic is called torqueslip characteristic, where slip is defined as speed relative to synchronous speed expressed as a fraction of synchronous speed. The rotor turns when the moving magnetic field induces a current in the shorted conductors. Disadvantages of 3 phase induction motor induction motor has low inherent starting torque draw large starting currents, typically 68 x their full load values speeds not easily controlled as dc motors operate with a poor lagging power factor when lightly loaded induction motor components an induction motor has two main parts. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Pdf this paper presents a competent approach to explain torquespeed, torquetime and speedtime characteristic of an induction motor. When a motor is designed in such a way that impedance of the aluminum. You should also make a dc measurement of stator winding linetoline resistance using a dmm.
Control of motor characteristics by squirrelcage rotor design. Pdf torquespeed characteristics of three phase squirrel. Starting torque, from stopped, running torque at rated rpm and hp output, stall torque, when prevented from running with power applied. Record all nameplate information for the induction motor. Torquespeed characteristics the torque developed by a 3ph induction motor depends on its speed but the relation cannot be represented by a simple equation. 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 slip characteristic of an induction motor low. The equation of the torque is given as shown below. It finally plots torque speed characteristics of induction motor.
211 1497 631 638 617 980 1443 1066 1243 1418 1411 290 60 1142 1004 931 58 152 1290 526 80 1413 1032 524 171 432 1151 1092 782 407 995 872 1428 1153