Highslip, induction motor, additional rotor, motor cooling. The rotor core is made up of steel laminations which have slots to accommodate formed 3single phase windings. Determination of the losses in induction machines due to harmonics pdf. 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 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. Selecting an oversized ac induction motor also reduces slip.
So slip of the induction motor is defined as the difference between the synchronous speed ns and actual speed of rotor i. As discussed earlier, a slip ring induction motor is an asynchronous motor, as the rotor never runs in synchronous speed with the stator poles. Ysalient features y robust and nonflammable construction. The basic idea of an electric motor is to generate two magnetic fields. The induction motor can be made easily and with that the price is rather low compared with other technologies. The singlephase stator winding produces a magnetic field that pulsates in strength in a. But the output torque developed decreases, if the slip increases. You should also make a dc measurement of stator winding linetoline resistance using a dmm. The difference, or slip, between actual and synchronous speed varies from about 0.
Introduction types of electrical machines types of 3ph induction motor basic principle working principle compnents of induction motor application comparision between 1ph i. The induction motor doesnt use a combustion process to deliver power so there is no need to refuel or air. If slip is zero then their is no relative speed between stator and rotor. Slip in electrical induction motors slip is the differentiation between synchronous and asynchronous speed.
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. 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standard squirrel cage ac motor by j van niekerk, zest weg group over a number of years slip ring motors have largely been replaced by standard squirrel cage ac induction motors, often in conjunction with ac variable speed drives vsds. The induction motor is made up of the stator, or stationary windings, and the rotor. Pdf design and analysis of drive system with slip ring. This document is highly rated by mechanical engineering students and. Figure illustrates the torque slip characteristics of an induction motor for the rated voltage. Induction motor theory jerry bednarczyk, pe course content introduction the ac induction motor is well suited to applications requiring constant speed operation. Portland slip ring induction motorsbrush holder problems. Package solution for slip ring induction motor with variable speed control sprs is part of the complete package for motor starting process. Well, it turns out that the desired steadystate slip of an induction motor can just as easily be set in a fieldoriented system by adjusting the ratio of d and q axis stator currents as shown in the following equation, where r r and l r are rotor resistance and rotor inductance, respectively, as shown in equation 1. 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. Fundamental wave model of lineoperated induction machine.
This type of rotor is provided with a 3phase, doublelayer, distributed winding consisting of coils used in alternators. The synchronous speed of an induction motor is the same fraction of the supply. The slip is defined as the ratio of difference of synchronous speed and actual rotor. 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 rotor will constantly be turning to align its magnetic field with that of the stator field. Slip in electrical induction motors engineering toolbox. Squirrel cage induction motor an overview sciencedirect topics. 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. Motor analysis block diagram induction motor starting can be analyzed using electrical, mechanical, and thermal models which interact as diagrammed in figure 1. Slip is the differentiation between synchronous and asynchronous speed. Slip of induction motor plays an important role in the operation of the induction motor. Torque slip characteristic of an induction motor the torque slip characteristic is represented by a rectangular hyperbola. Differential equations are solved using computer simulation.
This is seen that for a fixed value of slip, torque is equal to proportional to the square of voltage. Theseindividualrotormagneticfieldsproducea combine. Introduction to induction motor the engineering projects. Rotating magnetic field an overview sciencedirect topics. Larger motors exhibit less slip, and it gets smaller with a partial rather than full motor load. Slip torque characteristics of an induction motor my. This work has developed a steadystate and dynamic mathematical model of three phase slipring induction motors with external impedance. The threephase cage induction motor owes its good reputation as a rugged, problemfree drive unit not least to its good starting characteristics. 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.
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 summation of all torques acting on the motor shaft comprises the mechanical model. This is also called absolute slip or fractional slip and is denoted as s. When a large induction motor is running at its rated load and speed the slip will be only. This ensures stable operation of im in this region, for constant load torque. To explain clearly when there is relative speed between stator and rotor ample amount of emf is induced in th. It can be shown that the synchronous speed of a motor is determined by the following formula.
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. There are two major components of an ac induction motor. Design and analysis of drive system with slip ring induction motor for electric traction in india article pdf available in international journal of power electronics and drive systems 53. Combining with structure and distribution of heat source of. Starting, braking and positioning with threephase cage. 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. I havent messed with one of these beasts myself, so take this all with a grain of salt.
Torque slip characteristics of three phase induction motor. Thus, induction motor synchronous speed is defined by following equation 6. Torque slip characteristic of an induction motor low. The construction of a stator is the same for both the squirrel cage and slip ring induction motor. Hence the stable operating region of the motor lies for the slip values, s0, and that corresponds to maximum torque. Construction of three phase induction motor electrical4u. Concluding, advantage of induction motor is its simple operation, reliability and low cost. The maximum torque developed in an induction motor is called the pull out torque or the breakdown torque. Electromagnetic analysis of induction motor using fem. The magnetic winding is made by joining coils to form phases.
An induction motors rotor can be either wound type or squirrelcage type. Slip ring motor conversion to vsd driven standard squirrel. The slip ring induction motors usually have a phasewound rotor. The singlephase induction motor is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth. U, electrical engineering department abstract rotating electrical machines play an important role in the worlds industry. The cooling can be integrated so that the induction motor can work in a hermetically sealed environment for instance under water. Torque slip characteristics of induction motor electrical4u. The motor then runs as a singlephase induction motor. Introduction slip ring induction motors are widely used in industrial applications by varying rotor parameters. The slip in an induction motor is the difference between the main flux speed and their rotor speed. A squirrelcage induction motor is one in which the secondary circuit consists of a. The speed of the motor comes to zero, when the slip reaches to 1.
Pdf due to the loading effect on threephase induction motors or implemented speed control techniques, the rotational speed of the motor. Traditionally for the control of srim additional rotor resistances have been added. This system cordinates with the motor during the motor startup and makes it available for process control. 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. The motor is supplied from an inverter that provides an instantaneously controlled set of phase currents that combine to. Pdf highslip induction motor with additional rotor moveable. If the rotor is spun at exactly the same speed as the magnetic field generated by the stator windings, there is. For the immediate value of the slip, the graph changes from one form to the other. If the xaxis lies along the line joining the centres of poles rr, then the. It is expressed by the percentage of synchronous speed. Furthermore, the inherent slip of im allows multiple motors to be fed. Slip energy recovery of induction motor using converter. Electromagnetic analysis of induction motor using fem 1bhagat komal vipinchandra 2.
Y provides smooth and stepless cutting of resistance in rotor circuit of the motor, reducing starting current and. The 3phase set of currents, each of equal magnitude and with a phase. An induction motor can therefore be made without electrical connections to the rotor. The three phase induction motor is the most widely used electrical motor. An induction motor or asynchronous motor is an ac electric motor in which the electric current. Torqueslip speed characteristics of induction motor im. 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. 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. The torque slip curve for an induction motor gives us the information about the variation of torque with the slip. Slip in induction motor is the relative speed between the rotating magnetic flux and rotor expressed in terms of per unit synchronous speed. It should be noted that the slip is a very important factor in the induction motor. Cage induction machines institut fur elektrische energiewandlung. 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, it passes through the point of maximum torque when r 2 sx 20. This method is inefficient due to the wastages of power in the. Slip power recovery system for variable speed operation of. If the rotor windings are shorted and a start is attempted i. A single phase induction motor has two types of rotor. Record all nameplate information for the induction motor. Pdf selection of slip compensation technique in threephase. The most commonly used is the squirrel cage induction motor. Thus we cannot combine this rotor circuit with the stator equivalent circuit of fig. The required power is 10 hp at about 1,800 rpm and 1.
In the electrical model, the voltage, v, and the slip, s, determine the rotor current. The rotor speed is slightly lower than the synchronous speed by the slip frequency, typically 3%. A wide variety of low speed induction motor options are available to you, such as home appliance, car. According to the type of rotor, an induction motor is divided into two types. The alternating current ac induction motor is one of the most rugged and most widely used machines in industry. The value of slip in induction motor is can never be zero. The value of slip in induction motor at full load varies from about 6% for small motors to about 2% for large motors. Pdf this research focuses on the problem of selfcooled highslip induction motors. The torque produced by the induction motor is directly proportional to induction motor slip. Torqueslip characteristics, induction motors, assignment help. If the actual shaft rpm is 2200, then slip factor is 2100 22002200 0. Learn more about the construction and operation of a slip ring induction motor. In general, the induction motor is cheaper and easier to maintain compared to other alternatives. The frequency of the start voltage controls the synchronous speed.
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