Load test on threephase squirrel cage induction motor. Induction motors generally will have low starting torque compared to dc series motor. This work has developed a steadystate and dynamic mathematical model of three phase slipring induction motors with external impedance. What are the applications of a slipring induction motor. As with a squirrel cage induction motor, the rotor is the secondary winding to the primary stator winding. How to calculate the slip ring induction motor rotor current and voltage. From here no load current and the angle between voltage and. Differential equations are solved using computer simulation. The shape of the torqueslip curve of induction motor is. You should also make a dc measurement of stator winding linetoline resistance using a dmm. These tests are performed to check the electrical or mechanical defects of the induction motor. This means that the state of the carbon brushes and the slip ring rotor can be monitored, and cleaning can take place. Core loss is embedded with friction, windage and strayload loss m ind. Motor slip the rotor in an induction motor can not turn at the synchronous speed.
Form noload test i 0 is known and f 0 is found out as taking all quantities on per phase values. Speed control of three phase slip ring induction motor. For short circuit or blocked rotor test by adjusting. Slip in electrical induction motors engineering toolbox. Slip ring induction motor have big advantage of having high starting torque compared to squirrel cage motor. For load sharing to take place automatically, the motor speed should drop considerably as the load increases and this is ensured by using a motor having a high fullload slip, say for example 10%. This circle diagram is used to predict the performance of the machine at different loading. But the rotor construction differs with respect to the type of motor.
Copper losses at rotor side can be neglected in no load test because the slip is small at no load. Connection for load testing of a threephase induction motor. We have to perform no load and blocked rotor test in an induction motor. Noload and blocked rotor test on an induction machine aim to estimate magnetization and leakage impedance parameters of induction machine using noload and blocked rotor tests theory an induction machine in its equivalent circuit form is akin to a transformer with slip as an additional parameter. The open ends of the rotor winding are joined to three insulated slip rings. Read here to know about the starting arrangement and the role played by the external resistances in obtaining better starting characteristics. First noload test the noload test, like the open circuit test on a transformer, gives information about exciting current and rotational losses. Testing, application and failure analysis easa convention 20 mandalay bay resort las vegas, nv july 1, 20. In normal conditions, the slip ring motor functions like a squirrel cage motor. Load tests on a threephase induction motor and measurement of the inrush current objectives.
The ld language enables the description of tests and modifications of. Conduct no load test and blocked rotor test on the induction motor and find out the per phase. To construct the circle diagram three tests are to be performed, namely a noload test. It seems very odd that you want exactly four answers.
Ball and roller bearings are used to suit heavy duty, torublefree running. This article is devoted to slip ring induction motors. Fault identification of 3phase slip ring induction motor free download as powerpoint presentation. Number of poles, frequencies and synchronous induction motor speed. Wound rotor with slip rings the rotating magnetic field. The magnetization current im flowing in the motors equivalent circuit fig. At the time of normal running of induction motor, for a constant torque load, slip is proportional to rotor. What are four possible causes if the brushes for a slip. Setup of load characteristics of 3 phase slip ring induction motor. Noload and blocked rotor test on an induction machine aim. Theory of no load test of induction motor the impedance of magnetizing path of induction motor is large enough to obstruct flow of current. An induction motor can therefore be made without electrical connections to the rotor. Setup of load characteristics of 3 phase slip ring.
When a motor starts to rotate the slip is 100 % and the motor current is at maximum. This can be used in starting a slipring induction motor, for example. Slip ring motor is preferred over squirrel cage induction motor where a high starting torque is required b load. If the slip ring induction motor is started with all the slip rings or the rotor. We can react very quickly due to a comprehensive stock of slip ring motors in a power range up to 15000 kw. To conduct the load test on single phase squirrel cage induction motor and to draw the. Sketch of a crosssection of slip rings for an electric motor. Phasor diagram of induction motor on noload and loaded conditions, visualization of a threephase induction. Therefore slip ring induction motors are generally e. Adams engineering college, paloncha eee department emii lab experiment no.
The load test on induction motor is performed to compute its complete performance i. An induction motors rotor can be either wound type or squirrelcage type. An 8 pole, 50 hz slip ring induction motor runs at a slip of 2. In previous articles i have discussed the construction, operation, starting, speed control, and classes of squirrel cage induction motors. Designing of three phase squirrel cage induction motor for. Short out the slip rings and the motor will run just like a standard 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.
Department of electrical engineering national institute of. Fullload slip varies from less than 1 % in high hp motors to more than 56 % in minor hp motors. What external resistance per phase must be added in the rotor circuit so that the motor now runs ate a slip of 17. Also know about the qualities of slip ring induction motors.
To draw circle diagram for a three phase induction motor. The voltage and current is induced in the rotor circuit from the stator circuit for the operation. Review of the testing methods for fullload temperature. Wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. Therefore, small current is applied to the machine due to which there is a fall in the statorimpedance value and rated voltage is applied across the magnetizing branch.
Starting of slip ring induction motor explained in an easy. An induction motor is based on the principle of induction of voltages and currents. Induction motor and different speed control methods page no 3. Starting torque of slip ring motor and induction motor. What happens if the motor is started as a normal induction motor. The process is noninvasive, requiring only that a current transformer ampprobe or current clamp be placed around one conductor. Record all nameplate information for the induction motor. The rotor of the slip ring induction motor is also cylindrical or constructed of lamination. 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.
A 3 phase induction motor can be used for different applications with various speed and load requirements. Low starting current of the order of 250 to 350% of the full load current. Differential equations are solved using computer simulation and data for an induction machine are obtained from laboratory tests. The test is performed by applying balanced rated voltage on the stator. Stardelta starting of a three phase induction motor 10. The flywheel shares the load with the motor, thus enabling a motor of lower rating to be employed.
Fault identification of 3phase slip ring induction motor. How to calculate the slip ring induction motor rotor. The slip ring rotor chamber has two modification openings. Pdf three phase slip ring induction motor drive with slip power.
Hence slip ring motors are used where one or more of the above requirements are to be met. In an induction motor, noload the slip is generally. Induction motor torquespeed characteristics figure 6. During this test, the motor is operated at rated voltage and frequency and normally loaded mechanically by brake and pulley arrangement. To conduct the load test on 3phase induction motor. The temperature rise was found to be similar from both phantom loading test and actual test for the squirrelcage motor. The slip ring motor has very little application in industries. Because the motor load factor is an average of motor load during a period. 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. Power control analysis for different load torque using. The slip ring rotor chamber of the ic 411 slip ring induction motor is separated by what is known as a labyrinth seal, which prevents contamination from coal dust.
By adding load to the induction motor and decreasing the voltage at constant frequency the speed of induction motor falls to maintain load torque constant so mechanical losses will decrease. The construction of stator of the induction motor is almost the same as other motors. Equivalent circuit of an induction motor enables the performance characteristics which are evaluated for steady state conditions. The rotor and stator are separated by an air gap which allows free rotation of the rotor.
It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. Slip ring motors are normally used where additional torque is required to overcome the inertia of the. What are the advantages of slipring induction motor. Individual motors in those ranges have even lower load factors. Induction motor testing and evaluation summary as energy costs rise, more emphasis is being placed. Ppt induction motor powerpoint presentation free to. No load and blocked rotor test on an induction machine aim to estimate magnetization and leakage impedance parameters of induction machine using no load and blocked rotor tests theory an induction machine in its equivalent circuit form is akin to a transformer with slip as an additional parameter. A slip ring induction motor can be started with external resistance added in its rotor circuit. Slipring motor manufacturer menzel provides shortterm availability and adaptation, applicationspecific requirements and worldwide logistics. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Photograph your local culture, help wikipedia and win.
In no load test, the induction motor is run at no load and by two watt meter method, its total power consumed is calculated which is composed of no load losses only. But how does external resistance aid in better starting characteristics. A squirrel cage induction motor takes 600% to 700% of the full load current, but a slip ring induction motor takes a very low starting current approximately 250% to 350% of the full load current. Slip ring motor fundamentals brighthub engineering. However an increase in speed for both machines used in the test was observed during the phantom loading test. As a result of its extensive use in the industry, induction motors consumes considerable amount of. In this example, the slip rings have a brushlifting device and a sliding contact bar, allowing the sliprings to be shortcircuited when no longer required. Hence slip ring motors are used where one or more of the above requirements. This motor is much heavier than the 22kw slip ring motor and resistor bank so the crane had to be rerated as well.
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