Experiment 7 et 332b noload and starting characteristics. Squirrel cage wound rotor with slip rings the rotating magnetic field. 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. Know about the most popular and almost unbreakable construction of squirrel cage induction motor. The no load test is similar to the open circuit test on a transformer. The open circuit test performed on the transformer. Studying and improving of squirrel cage induction motor scim efficiency is a continuous area of interest not only among the researchers but also the industry, manufacturer and government. Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. In this test, a rated, balanced ac voltage at a rated frequency is applied to the stator while it is running at no load.
For a fullload operating slip of 3 per cent, the speed will then be 1. Circuit shown below is for no load test to obtain more reliable values ranges of both wattmeter should be 5a, 500 v for no load test. Motor guide february 2014 low voltage motors motor guide. However, with variable frequency drives, these disadvantages can be overcome. But the rotor construction differs with respect to the type of motor. No load and blocked rotor tests, obtained from the above motors. Hp squirrelcage induction motor which you have to parameterize. An induction motor can therefore be made without electrical connections to the rotor. Example no load blocked rotor tests the results of the no load and blocked rotor tests on a threephase, 60 hp, 2200 v, sixpole, 60 hz, class a squirrel cage induction motor are. The following is a description of the four different classes of squirrelcage motors. Particularly, the squirrel cage type is simplicity, robustness and low cost, which has always made it very goodlooking and therefore, captured the leading place in industrial sector. They are used in situations where large power is required.
An induction motor s rotor can be either wound type or squirrelcage type. In the slip ring motor, the rotor winding is short circuited through the slip rings. Information guide for general purpose industrial ac small and medium squirrelcage induction motor standards. Characteristics of induction motors nidec corporation. But increasing the rotor resistance for improving starting torque is not advisory as it will reduce the efficiency of the motor due to more copper loss. Pdf this paper describes a set of tests carried out on an induction motor for a 75 kw escalator.
Squirrelcage induction motors draw a large lagging current at noload since the magnetic circuit includes an air gap. This rotor is a cylinder of steel laminations, with highly. Gradually apply three phase voltage across motor stator terminals via the autotransformer d. Low and high voltage three phase induction motors m line squirrel cage rotor horizontal date. Horizontal squirrel cage mediumvoltage induction motor. Principles of operation of induction motors the stator of an induction motor is similar to that of a synchronous machine, and in the case of a machine supplied with threephase currents, a rotating magnetic flux is. Different method of starting of threephase squirrel cage induction. Squirrel cage rotor almost 90 per cent of induction motors are squirrel cage type. In squirrel cage induction motors, rotor windings wound in squirrel cage. A n power analyser power analyser 230v 50hz variable frequency drive a v 3 phase im mechanical load figure 5. Most of the current goes to i m, since x m is much smaller than r fe. Under both supply conditions, the performance of a 5 hp threephase squirrel cage induction motor was measured through a real load test. The resulting power factor of the unloaded induction motor is very low 0. Noload and load tests on 3 phase induction motors used in.
April 11, 20 1 of 10 experiment induction motor threephase induction motors 208v ll objective this experiment demonstrates the performance of squirrelcage induction motors and the method for deriving electrical equivalent circuits from test data. To obtain the load performance characteristics of a threephase squirrel cage induction motor. Torquespeed characteristics of three phase squirrel cage. Dcar of explosionproof, watercooled squirrel cage induction motors scim are. Threephase squirrelcage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. From the data obtained from the no load test, we can determine the values for the series circuit elements r. The squirrel cage induction motor the slip ring induction motor in this laboratory, we use the squirrel cage induction motor. This test is similar to the open circuit test on transformer. Motors employing this type of rotor are known as squirrel cage inductionmotors. Abb motors and generators 9akk105285 en 022014 5 42 4.
To measure the inrush current when the motor starts. To obtain on load current and its power factor angle. Actually, to achieve synchronous speed in an induction motor is impossible. The squirrel cage induction motor was designed for an extended service life under very demanding. Motors employing this type of rotor are variously known asphasewound motors or wound motors or as slipring motors. This test tells us the magnitude of constant losses occurring in the motor. Normally, we use the motors in industrial drives because they are rugged, reliable and economical. Load tests on a threephase induction motor and measurement of the inrush current objectives.
Low starting current of the order of 250 to 350% of the full load current. Menzel squirrel cage induction motors are manufactured for various industries and industrial applications of all kinds. Pdf improving squirrel cage induction motor efficiency. Blocked rotor test of an induction motor the blocked rotor test of an induction motor is similar to the short circuit test of a transformer. Information guide for general purpose industrial ac small. Circuit diagram for vf control the cut section of a squirrel cage induction motor is shown in fig. However, should the motor require service, this manual includes a section that assists the. Hence slip ring motors are used where one or more of the above requirements are to be met. First the measured i 1 and the measured phase power p ph are used to calculate. No load test is intended to detect hidden defects that are. To find these values, we draw graphs of power and line current versus applied voltage as shown in figure 14.
Almost 95% of the induction motors used is of squirrel cage type. As the name suggest no load test is performed when rotor rotates with synchronous speed and there is no load torque. The possibility of the efficiency improvement for the three phase, low voltage, squirrel. Jul 25, 2019 a 3 phase squirrel cage induction motor is a type of three phase induction motor which functions based on the principle of electromagnetism. A three phase, 50 hz, 6 pole squirrel cage induction motor runs at 960 rpm on full load.
Load test on single phase squirrel cage induction motor aim. The actual load tests were also performed in the motors in accordance with is 12615. Hp squirrel cage induction motor which you have to parameterize. Noload and blocked rotor test on an induction machine. Teco totally enclosed fan cooled squirrelcage induction motors are designed, manufactured and tested to meet or exceed the latest nema, ieee, csa and other international standards. Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. Perform no load and block rotor test on 3 phase induction motor. Two digital multimeters and fluke power quality meter with banana cables from the. The set up for no load test of induction motor is shown in the figure. 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. The main disadvantage of squirrel cage induction motor is poor speed control and low starting torque. Express the maximum torque developed in terms of full load toque. No load test of induction motor your electrical guide. In simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel cage induction motor.
Also appreciate the rugged construction of squirrel cage rotor and know the spectacular reasons for the skewed arrangements of the rotor conductors. Designing of three phase squirrel cage induction motor for. In this test, the alternator is run with the prime mover i. The squirrel cage induction motors are 90% used in various industrial, domestic and commercial applications. Advantages and disadvantages of squirrel cage induction motor.
Instruments connected in the circuit serve the function indicated against each. Information guide for general purpose industrial ac small and. This rotating magnetic field has a speed which is known as the synchronous speed this rotating magnetic field induces the voltage in rotor bars and hence shortcircuit currents start flowing in the rotor bars. Three phase induction motors are one of the most popular electric motors commonly found in processing plants or any manufacturing concern. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. In this test, the shaft of the motor is locked so that it cannot move and the rotor winding is short circuited. The load test on induction motor is performed to compute its complete performance i. Routine test of three phase induction motor vishant naik1, saurabh k singh2, sahil chawhan3. The motor was a squirrel cage induction motor, tefv. Noload test the slip of the induction motor at noload is very low. The squirrel cage brand is the most popular and they perform various tasks wherever they are applied.
Schematic diagram for load test on three phase induction motor 3 phase variac to limit the starting current of the motor ammeter to measure the current drawn by the stator. To obtain the load performance characteristics of a threephase squirrelcage induction motor. Nema design b considered a standard type with normal starting torque, low starting current, and low slip at full load. The machine is started in the usual way and runs unloaded from normal voltage mains. Teco totally enclosed fan cooled squirrel cage induction motors are designed, manufactured and tested to meet or exceed the latest nema, ieee, csa and other international standards. Disconnect any mechanical load connected to the induction motor. Almost 70% of the industrial motors and drives comes under these category. Thus no load and blocked rotor tests are performed on the motors. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used.
Starting torque is directly proportional to the rotor resistance. Note down the machine ratings and calculate rated current of the machine noload test. Two digital multimeters and fluke power quality meter. The stand still rotor resistance and reactance per phase are 0. These motors are very robust in construction and very cheap. To conduct the load test on single phase squirrel cage induction motor and to draw the performance characteristics curves. Squirrel cage motors have a rotor with short circuited bars whereas slipring motors have wound. It is called a squirrel cage motor because the rotor inside of it known as a squirrel cage rotor looks like a squirrel cage.
April 11, 20 1 of 10 experiment induction motor threephase induction motors 208v ll objective this experiment demonstrates the performance of squirrel cage induction motors and the method for deriving electrical equivalent circuits from test data. Selection of induction motors for industrial applications. Menzel squirrel cage motors are available in all standard motor cooling and protection types for lowvoltage from 75 kw as. A lowresistance rotor develops low slip and high efficiency at full load. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. Know about the different winding slots, lamination of the stator and its construction. How are squirrel cage induction motors constructed. The most popular squirrel cage induction motor is of a 4pole design. Pdf noload and load tests on 3 phase induction motors used in. The induction motors are simple and of rugged design, low maintenance, low cost and most suitable means for such applications. Noload and blocked rotor tests, obtained from the above motors. The circuit diagram of load test on 3 phase squirrel cage induction motor. An induction motor s rotor can be either wound type or squirrelcage.
Basically, it is the construction of rotor which makes squirrel cage induction motor different from wound type induction motor. These motors are suitable for all general applications where an open machine is not applicable due to severe environments such as excessive dirt, dust andor moisture. Introduction this manual provides information on how to safely install, couple to the driven equipment, and maintain the toshiba squirrel cage mediumvoltage induction motor. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. These test results are used to determine the equivalent circuit parameters of each motor.
Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. Singlephase induction motors are used extensively for smaller loads, such as household appliances like fans. Squirrel cage induction motors have poor starting torque and high starting currents. No load test of an induction motor no load test is an indirect method used for determining the efficiency and also to determine the circuit parameters of the equivalent circuit of the threephase induction motors. Circuit diagram for no load and blockedrotor test on 3 phase induction motor a. Squireel cage induction motors are widely used in industries. Nema design b considered a standard type with normal starting torque. Working principle of 3 phase squirrel cage induction motor. Separate view of the stator and rotor of an induction motor is. Pdf performance analysis of a threephase squirrelcage.
The reason for the name squirrel cage is because of the type of rotor used in these motors. In the equivalent circuit r 1 represents, the resistance of the stator winding and x 1 the stator leakage reactance flux that does not link with the air gap and rotor. The construction of stator of the induction motor is almost the same as other motors. Note down the machine ratings and calculate rated current of the machine no load test. To determine the equivalent circuit parameters of an induction motor. Squirrel cage induction motor the engineering projects. From the data obtained from the noload test, we can determine the values for the series circuit elements r. And on the other hand, when designed to have a high impedance, the motor has an increased amount of torque in a lowspeed range. Noload and blocked rotor test on an induction machine aim theory. Power levels of polyphase squirrel cage induction motors at no load. Squirrel cage motors are the most commonly used induction motors, but the main drawback in them is their poor starting torque due to low rotor resistance. With indian and international standards almost similar for the induction motors, squirrel cage or wound rotor, the replacement is extremely easy and fast reducing downtime of outage, which is vital for sustaining. The stator winding is assumed to be yconnected with the access to the phase terminals.
Circuit diagram for noload and blockedrotor test on 3 phase induction motor a. Construction of squirrel cage induction motor explained. Squirrel cage induction motors menzel elektromotoren. Similarly the range of ammeter and voltmeter during no load test should be 5a, 500 v. Test facilities our test room is able to perform testing on high efficiency motors in compliance with the iec 6003421. Notice and disclaimer the information in this publication was considered technically sound by a consensus among persons engaged in its development at the time it was approved. No load test is same as the open circuit test performed on the transformer.
Aug 25, 2018 thus no load and blocked rotor tests are performed on the motors. Induction motor equivalent circuit from the preceding, we can utilise the equivalent circuit of a transformer to model an induction motor. This motor should be mounted on the motor bench, wherein the motor shaft may be coupled to the dynamometer for taking the measurements. The no load test of 3 phase induction motor is performed on induction motor when it is running without load.
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