Jul 25, 2019 squirrel cage induction motor working principle. Conveyors, ball mils and crane hoists are common applications for wound rotor motors, because of their. Know about the most popular and almost unbreakable construction of 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. With a 60 cycle power supply the synchronous speeds available are. For a squirrelcage motor, the rotor as represented in figure 2 is constituted by a system of bars in copper or aluminum, which are coaxial to the rotation axis and directly diecast in the slots made along the external periphery of the ferromagnetic.
A squirrel cage rotor is the rotating part of the common squirrel cage induction motor. So the main idea behind motor maintenance is to prevent breakdown rather than repairs them. Pdf monitoring and simulation of threephase squirrelcage. A blocked rotor test is conducted on an induction motor. Slip ring induction motor is made up from wound rotor and squirrel cage induction motor is made up from the squirrel cage rotor. How are squirrel cage induction motors constructed. Model repair specifications for low voltage induction motors. Load tests on a threephase induction motor and measurement of the inrush current objectives. But the rotor construction differs with respect to the type of motor. Testing of increased safety ht induction motor for. Almost 95% of the induction motors used is of squirrel cage type.
There is no electrical connection between these bars. Closedform analysis of squirrelcage induction motors with. A 3 phase induction motor has two types based on the rotor construction, named as. The purpose of this article is to dispel some misconceptions about how they work, and to offer valuable tips for failure analysis, repair and testing. Review of electrical tests to assess motor windings. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrelcage rotor. Construction of squirrel cage induction motor explained. The reason for the name squirrel cage is because of the type of rotor used in these motors. Abb offers two types of low voltage induction motor series.
Electrical, mechanical, and thermal motor characteristics define the frame needed for effective motor protection running stage, starting stage, and lockedrotor conditions serve to determine the main motor parameters motor heating and thermal damage motor characteristics depend on both positiveand negativesequence current in the. Medium squirrel cage induction motor standards published by national electrical manufacturers association. Information guide for general purpose industrial ac small and medium squirrelcage induction motor standards. The rotor will constantly be turning to align its magnetic field with that of the stator field. A motor rating of 10 horse power, 415 volts with 1440 rpm and 4pole is selected for design problem and an. In addition to conventional squirrel cage rotor testing methods such as the growler test, techniques that will also be covered are the use of a core. Designing of three phase squirrel cage induction motor for. The synchronous speed of a motor is determined by the power supply and the number of poles built into the structure of the winding. The main purpose of the information that will be presented here is to describe many of the available tests that can be utilized under these different circumstances. Three phase squirrel cage induction motors specifications and standards general specifications rated outputs and effi ciency values are in accordance with iec 60034301. Conveyors, ball mils and crane hoists are common applications for. Three phase squire cage induction motor, fully enclosed.
Apr 15, 2020 in the induction motor, as in all motors, electrical energy is converted into mechanical energy. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. Testing with the motor disassembled testing the rotors of disassembled ac induction motors has certain advantages. Maxwells equations in squirrelcage induction motors. After the maximum torque point which is three to four times the fullload torque, the decrease in rotor p. Hence the fully loaded woundrotor motor turns at 3,600 rpm on 60 hz.
The theory of three phase induction squirrel cage motors. Slipring induction motor also known as rotor resistance start motor. A typical 3phase squirrel cage motor has six connection leads in the electrical connection box for the three coils. Firstly, i am going to tell you about the structure of squirrel cage induction motor. To measure the inrush current when the motor starts. The primary focus of this session is to describe many of the available tests that can be utilized in the service center or at the motor installation site. Induction motor, no load test, blocked rotor test, vibration test, temperature. Torquespeed characteristics of three phase squirrel cage induction motor aim to obtain the torquespeed characteristics tn r of a three phase squirrel cage induction motor using 1. Parameters estimation of squirrelcage induction motors. Also appreciate the rugged construction of squirrel cage rotor and know the spectacular reasons for the skewed arrangements of the rotor conductors. Testing and assessment of ex e motor the designed ex e ht squirrel cage induction motor are tested and assessed for performance of motor to ensure that these designed motor will not be unsafe in hazardous area. Because of the critical roles these motors play in any plant, a failure of the motor, inability to start, noisy operation and sundry other problems need to be remedied as soon as. Working principle of 3 phase squirrel cage induction motor.
Expanding on the growler testing of squirrel cage rotors, a popular variation from using a hack saw blade is to put magnetic particle paper over the rotor section that the growler coil is inducing current into. Jan 03, 2016 what is the three phase induction motor working principle. The squirrel cage brand is the most popular and they perform various tasks wherever they are applied. This rotating magnetic field has a speed which is known as the synchronous speed. The circuit diagram of load test on 3 phase squirrel cage induction motor. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents. To obtain the load performance characteristics of a threephase squirrel cage induction motor. Pdf this paper describes a set of tests carried out on an induction motor for a 75 kw escalator. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. Rotor testing with mce pdma a leader in electric motor. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Ieee std 432000ieee recommended practice for testing insulation resistance of rotating machinery electric machine parameter and testing part 4. The basic idea of an electric motor is to generate two magnetic fields. Normally, we use the motors in industrial drives because they are rugged, reliable and economical.
In a squirrel cage induction motor, the rotor has conductive bars embedded in slots in the laminations, running the length of the rotor. The hysteresis motor takes advantage of the wide hysteresis loop in the highcoercivity cobaltsteel rotor. For motors falling outside this description, the more comprehensive model specifications below are recommended. Find, read and cite all the research you need on researchgate. Determining whether or not a squirrel cage rotor is defective is an issue that is a challenge to every service center as there is often no simple way to determine the integrity of a rotor. A 3 phase squirrel cage induction motor is a type of three phase induction motor which functions based on the principle of electromagnetism. The primary focus of this session will be to describe many of the available tests that can be utilized in the service center or at the motor installation site. This hundredyearold motorinvented by the great scientist nikola teslais the most common motor type.
A squirrel cage rotor slips behind synchronous speed. 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. Test methods with the motor assembled, and test methods with the motor disassembled. In operation, the nonrotating stator winding is connected to an alternating current power source. 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. Motors of this type employ squirrel cage having relatively low resistance and reactance. The three most common starting methods for squirrel cage motors are pws part winding start, wds wyedelta start, and electronic softstart.
The maximum torque of a squirrel cage induction motor is also called pullout torque because of the way the motor reacts to an overload. The rotor of an induction motor is like the secondary. If the turn insulation fails in a formwound stator winding, the motor will likely fail in a few minutes. Practical aspects of rotor cage fault detection for medium. This final thesis will mostly be dedicated to induction motors but also to synchronous permanent magnet and reluctance motors. A typical 3phase squirrelcage motor has six connection leads in the electrical. Dec 01, 2017 slipring induction motor also known as rotor resistance start motor. A wound rotor motor runs synchronous with line frequency. The motor efficiency class and nominal motor efficiency must be stated on the. Testing of increased safety ht induction motor for hazardous area.
Jan 11, 2019 reluctance motors are not selfstarting. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used. Slipring induction motor connection and testing youtube. In the transient behavior analysis of a squirrelcage induction motor, the parameters of the singlecage and doublecage models are studied. Diagnostics of rotor and stator problems in industrial. In addition to conventional squirrel cage rotor testing methods such as the growler test, also covered will be. The cylindrical squirrel cage consists of heavy copper, aluminum, or brass bars set into grooves and connected at both ends by conductive rings that electrically short the bars together. In this project, two kinds of induction motor faults, stator short circuit fault and bro ken rotor bar fault. Former is cheaper and broadly used as it requires less maintenance than later one. Information guide for general purpose industrial ac small. It is called a squirrel cage motor because the rotor inside of it known as a squirrel cage rotor looks like a squirrel cage. Instruments connected in the circuit serve the function indicated against each. Two digital multimeters and fluke power quality meter with banana cables from the.
Some of the electrical energy supplied to the stator is read more power flow in an induction motor. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. Diagnostics of rotor and stator problems in industrial induction motors. With a 60 cycle power supply the synchronous speeds available are 3600 rpm, 1800 rpm, 1200 rpm and 900 rpm. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface.
Squirrel cage induction rotors can be one of the toughest things to analyze. This hundredyearold motorinvented by the great scientist. In this test, the rotor of the induction motor is blocked. An induction motor can therefore be made without electrical connections to the rotor. Horizontal squirrel cage mediumvoltage induction motor. Variable voltage variable frequency vf control theory an induction motor compared to a dc motor has some major advantages such as. The tests and assessment for the ex e motors are as follows. Due to high input frequency from laboratory supply, the analysis of power loss made by hysteresis and eddy current become very important. Testing of a squirrel cage rotor requires some under standing of how the rotor functions. The most commonly used motors are squirrel cage induction motors. Torquespeed characteristics of three phase squirrel cage. Because of the critical roles these motors play in any plant, a failure of the motor, inability to start, noisy operation and sundry other problems need to be remedied as soon as possible to avoid costly production downtime. Parameters estimation of squirrelcage induction motors using ann and anfis.
Slipring induction motor connection and testing people education online. The theory of three phase induction squirrel cage motors m. Aug 31, 2017 the invention of induction motors permanently altered the course of human civilization. There are two types of induction motors, one with wound type rotor, also called slipring motor and another one with squirrel cage rotor. The panel required for testing of the real system under test is use of line. By far the most commonly used ac motor is the induction motor. Pdf locked rotor shortcircuit test lrt performed on squirrel cage motors is part of the motor routine test. Three most common starting methods for squirrel cage motors. This work is introducing the designing of new three phase squirrel cage induction motor with an objective of getting good efficiency. The invention of induction motors permanently altered the course of human civilization. Standard types of squirrel cage motors are as explained below. The motor was a squirrel cage induction motor, tefv. Induced current serves the same purpose as dc current delivered to a wound rotor. Our test motor with squirrel cage has a circumferential speed of 40 ms.
An induction motors rotor can be either wound type or squirrelcage type. The stator carries a 3phase winding called stator winding while the rotor carries a short circuited winding called rotor winding. Though viewing the rotor can make fault identification easy, in the case of squirrel cage induction rotors, seeing is not always believing. However, should the motor require service, this manual includes a section that assists the repair technician with maintenance, disassemblyassembly, part replacement, and. The iec 60034301 is part of an effort to unify motor testing standards, efficiency requirements and product. Model repair specifications for low voltage induction motors these model repair specifications are intended to cover routine repair and rewind of lowvoltage randomwound threephase ac squirrel cage induction motors. Test results of induction motor broken rotor bar fault. Slippage induces current into shorted turns formed by the squirrel cage. Pdf improving squirrel cage induction motor efficiency. High speed im with appropriate squirrel cage can reach circumferential speed up to 200 ms, see in 2. Squirrel cage induction motor requires significantly less maintenance as it does not contain brushes, commutators, slip rings. The load test on induction motor is performed to compute its complete performance i.
The rotor winding derives its voltage and power from the externally. Routine test of three phase induction motor vishant naik1, saurabh k singh2, sahil chawhan3, jatin wankhede4. Since here we are talking about maintenance of induction motor, and it is of two types. However, a blocked rotor current test is conducted on squirrel cage rotor motors. Squirrel cage induction motor and wound rotor induction motor. Direct starting of squirrelcage induction motors with direct starting, the poles of contactor and motor protective device are connected to the pole conductors figure 1 and the operating current of the motor flows through them.
Oct 09, 2016 a 3 phase induction motor has two types based on the rotor construction, named as. Telecommunication engineering, southwest jiaotong university, china, 2005 thesis submitted for the degree of masters of engineering science in school of electrical and electronic engineering the university of adelaide, australia august 2010. If someone works with ac 3phase motors, then it is important to know how to connect these motors in star and delta connection, and how to detect an electrical problem. These motors are tested to strict quality control for routine and type tests at every stage of production and are ideally suitable for various industrial applications. What is the difference between a squirrel cage motor and a. Squirrel cage induction motor the engineering projects.
The 3phase set of currents, each of equal magnitude and with a phase. Some of the electrical energy supplied to the stator is. The most popular squirrel cage induction motor is of a 4pole design. The fault severity index can indicate the possibility of a rotor cage fault even in the absence of baseline data. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm. Rotor defects were estimated to be responsible for approximately 10% of motor failures based on a 1980s research effort on squirrel cage induction motors. It consists of a cylinder of steel laminations, with aluminum or copper. Most modern induction motors have a rotor in the form of a squirrel cage. Poloujadoff laboratoire delectrotechnique, universites paris, 6 et 11 ua 845 batiment 214, orsay, 91405, france pages 245264.
For this reason, special windings called squirrel cage windings are frequently built into the rotor, so the reluctance motor starts as an induction motor. Test procedure for polyphase induction motors and generators. Know about the different winding slots, lamination of the stator and its construction. Few methods exist that instill the confidence you need to make a call, and. Like any electric motor, a 3phase induction motor has a stator and rotor. Each serves approximately the same purpose but is dependent upon the number of contactors provided. In the induction motor, as in all motors, electrical energy is converted into mechanical energy. These bars are shorted at each end with shorting rings.
The study of steady state operation of squirrel cage induction machines may be seen from the point of view of the theory of circuits with periodically variable mutual inductances. A typical 3phase squirrelcage motor has six connection leads in the electrical connection box for the three coils. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. The construction of stator of the induction motor is almost the same as other motors. Diagnostics of rotor and stator problems in industrial induction motors by fang duan b.