The slip is defined as the ratio of difference of synchronous speed and actual rotor. This ensures stable operation of im in this region, for constant load torque. An induction motors rotor can be either wound type or squirrelcage type. The motor then produces a constant torque and not a pulsating torque as in other singlephase motors. If the slip is zero, what is the speed of a induction motor. Mar 12, 2020 torqueslip speed characteristics of induction motor im threephase induction motor mechanical engineering notes edurev is made by best teachers of mechanical engineering. The speed of the motor comes to zero, when the slip reaches to 1. Highslip, induction motor, additional rotor, motor cooling.
The induction motor is made up of the stator, or stationary windings, and the rotor. Torque slip characteristic of an induction motor the torque slip characteristic is represented by a rectangular hyperbola. Pdf due to the loading effect on threephase induction motors or implemented speed control techniques, the rotational speed of the motor. The induction motor can be made easily and with that the price is rather low compared with other technologies. A squirrelcage induction motor is one in which the secondary circuit consists of a. Slip in electrical induction motors slip is the differentiation between synchronous and asynchronous speed. Pdf highslip induction motor with additional rotor moveable.
Fundamental wave model of lineoperated induction machine. The threephase cage induction motor owes its good reputation as a rugged, problemfree drive unit not least to its good starting characteristics. Torque slip characteristics of three phase induction motor. The required power is 10 hp at about 1,800 rpm and 1. The singlephase stator winding produces a magnetic field that pulsates in strength in a. The basic idea of an electric motor is to generate two magnetic fields. Slip energy recovery of induction motor using converter. The synchronous speed of an induction motor is the same fraction of the supply. The 3phase set of currents, each of equal magnitude and with a phase. Hence the stable operating region of the motor lies for the slip values, s0, and that corresponds to maximum torque. Synchronous motor speed and slip an interesting characteristic of induction motors is that the actual speed of the rotor always lags the progression of the magnetic field around the stator. Introduction slip ring induction motors are widely used in industrial applications by varying rotor parameters. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip.
If slip is zero then their is no relative speed between stator and rotor. If the rotor windings are shorted and a start is attempted i. Construction of three phase induction motor electrical4u. This document is highly rated by mechanical engineering students and. An induction motor can therefore be made without electrical connections to the rotor. Pdf design and analysis of drive system with slip ring. Thus, it passes through the point of maximum torque when r 2 sx 20.
The value of slip in induction motor is can never be zero. For induction motors a very important parameter is the slip of the motor the slip, s, defines the relative speed difference between synchronous speed and rotor speed and is given by. What is slip in an induction motor, how it is calculate and all the details about slip in an induction motor is given in this video watch other videos. Y provides smooth and stepless cutting of resistance in rotor circuit of the motor, reducing starting current and. Slip of induction motor plays an important role in the operation of the induction motor. The motor is supplied from an inverter that provides an instantaneously controlled set of phase currents that combine to. But the output torque developed decreases, if the slip increases. The three phase induction motor is the most widely used electrical motor. An ac alternating current induction motor consists of a stator and a rotor and the interaction of the currents flowing in the rotor bars and the rotating magnetic field in the stator generates the torque that turns the motor. Record all nameplate information for the induction motor. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. The cooling can be integrated so that the induction motor can work in a hermetically sealed environment for instance under water. I havent messed with one of these beasts myself, so take this all with a grain of salt.
So slip of the induction motor is defined as the difference between the synchronous speed ns and actual speed of rotor i. Theseindividualrotormagneticfieldsproducea combine. If the rotor is spun at exactly the same speed as the magnetic field generated by the stator windings, there is. Torqueslip speed characteristics of induction motor im. A slip is created between these fields, when a load is applied to the motor compared to the synchronous speed, the rotor speed decreases at higher slip values. An induction motor or asynchronous motor is an ac electric motor in which the electric current. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. Selecting an oversized ac induction motor also reduces slip. Combining with structure and distribution of heat source of. The rotor will constantly be turning to align its magnetic field with that of the stator field.
The torque produced by the induction motor is directly proportional to induction motor slip. Slip in electrical induction motors engineering toolbox. 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. If the actual shaft rpm is 2200, then slip factor is 2100 22002200 0. This work has developed a steadystate and dynamic mathematical model of three phase slipring induction motors with external impedance. U, electrical engineering department abstract rotating electrical machines play an important role in the worlds industry.
The induction motor doesnt use a combustion process to deliver power so there is no need to refuel or air. Learn more about the construction and operation of a slip ring induction motor. 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. A wide variety of low speed induction motor options are available to you, such as home appliance, car. This method is inefficient due to the wastages of power in the. Thus, induction motor synchronous speed is defined by following equation 6. Portland slip ring induction motorsbrush holder problems. Motor analysis block diagram induction motor starting can be analyzed using electrical, mechanical, and thermal models which interact as diagrammed in figure 1. Concluding, advantage of induction motor is its simple operation, reliability and low cost. This is seen that for a fixed value of slip, torque is equal to proportional to the square of voltage. Pdf selection of slip compensation technique in threephase.
Slip ring motor conversion to vsd driven standard squirrel cage ac motor by j van niekerk, zest weg group over a number of years slip ring motors have largely been replaced by standard squirrel cage ac induction motors, often in conjunction with ac variable speed drives vsds. This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. When a large induction motor is running at its rated load and speed the slip will be only. It should be noted that the slip is a very important factor in the induction motor. It is expressed by the percentage of synchronous speed. A single phase induction motor has two types of rotor. You should also make a dc measurement of stator winding linetoline resistance using a dmm. Larger motors exhibit less slip, and it gets smaller with a partial rather than full motor load.
The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. Rotating magnetic field an overview sciencedirect topics. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. The magnetic winding is made by joining coils to form phases. The rotor speed is slightly lower than the synchronous speed by the slip frequency, typically 3%. A slip ring, three phase induction motor rotates at a speed of 1440rpm, when a supply of 400v, 50hz is applied across the stator terminals. Thus we cannot combine this rotor circuit with the stator equivalent circuit of fig. The frequency of the start voltage controls the synchronous speed. Differential equations are solved using computer simulation.
Pdf this research focuses on the problem of selfcooled highslip induction motors. The summation of all torques acting on the motor shaft comprises the mechanical model. Torque slip characteristics of induction motor electrical4u. Slip power recovery system for variable speed operation of. It can be shown that the synchronous speed of a motor is determined by the following formula. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. The slip ring induction motors usually have a phasewound rotor. Torque slip characteristic of an induction motor low. Ysalient features y robust and nonflammable construction. 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 motor then runs as a singlephase induction motor. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Determination of the losses in induction machines due to harmonics pdf. Furthermore, the inherent slip of im allows multiple motors to be fed. Electromagnetic analysis of induction motor using fem 1bhagat komal vipinchandra 2. The alternating current ac induction motor is one of the most rugged and most widely used machines in industry. According to the type of rotor, an induction motor is divided into two types. If i increase the load torque, as the load torque increases, the new operating point has higher slip compared with that of point a which in turn means that speed of induction motor has decreased, and hence operating point a is stable. The most commonly used is the squirrel cage 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. The difference, or slip, between actual and synchronous speed varies from about 0. Cage induction machines institut fur elektrische energiewandlung.
The maximum torque developed in an induction motor is called the pull out torque or the breakdown torque. For the immediate value of the slip, the graph changes from one form to the other. Squirrel cage induction motor an overview sciencedirect topics. Figure illustrates the torque slip characteristics of an induction motor for the rated voltage. Traditionally for the control of srim additional rotor resistances have been added. Slip ring motor conversion to vsd driven standard squirrel. This system cordinates with the motor during the motor startup and makes it available for process control. In this type of three phase induction motor the rotor is wound for the same number of poles as that of stator but it has less number of slots and has less turns per phase of a heavier conductor.
Electromagnetic analysis of induction motor using fem. Induction motor the downside of the slip ring motor is that slip rings and brush assemblies need regular maintenance, which is a cost not applicable to the standard cage motor. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process. Torqueslip characteristics, induction motors, assignment help. Starting, braking and positioning with threephase cage. The slip in an induction motor is the difference between the main flux speed and their rotor speed. Slip is the differentiation between synchronous and asynchronous speed. To explain clearly when there is relative speed between stator and rotor ample amount of emf is induced in th. Introduction to induction motor the engineering projects. There are two major components of an ac induction motor.
1586 1275 1091 1089 759 342 658 363 1562 779 1126 760 346 114 864 709 559 979 671 1329 1035 67 251 1434 706 902 378 50 157 645 615 600 134 1039 181 657 1140 1235 652 805 1022 932 893 701 756 180 116