Working principle of 3 phase squirrel cage induction motor. This article will explain the principles of squirrel cage motors, how they operate, and what kinds of applications they are used for. Most of 3phase induction motors use squirrel cage rotor as it has a remarkably simple and robust construction enabling it to operate in the most adverse circumstances. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Woundrotor motors are also available, usually for special application where external resistance is applied to the rotor for speed control, as described later. We use different starters for both the type of three phase induction motors. The polyphase induction motor the polyphase induction motor is the most commonly used industrial motor, finding application in many situations where speed regulation is not essential. Nema mg 1, motors and generators provides design letters for polyphase induction squirrelcage medium motors. We use starters in order to limit the high starting current. Motors with nameplate volt ages different than those listed in tables 1 or 2 should be referred to the company. Nema mg 1, motors and generators provides design letters for polyphase induction squirrel cage medium motors. Parida department of electrical engineering national institute of technology, silchar,assam, india email. Horizontal squirrel cage mediumvoltage induction motor.
Ac motors polyphase peerless electric designs 3phase motors from 120 to 50 hp in various frame sizes from 4. Normally, we use the motors in industrial drives because they are rugged, reliable and economical. Our polyphase squirrel cage induction motors are designed for across the line or increment starting as required. In the circle diagram for induction motor, the diameter of the circle represents. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes. The rotor consists of a cylindrical lamina ted core with parallel slots for carrying the rotor conductors which, it should be fig. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. In operation, the nonrotating stator winding is connected to an alternating current power source. The vibration of squirrelcage induction motors usually. Model repair specifications for low voltage induction motors. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Available squirrel cage induction motor starting methods include directonline starting, reducedvoltage reactor or autotransformer starting, stardelta starting or, increasingly, new solidstate soft assemblies and, of course, variable frequency drives vfds.
The most common type of motor in this group is the squirrel cage polyphase induction motor so called because the rotor is constructed like a. It converts electrical energy into mechanical energy and it is used to provide motion. Polyphase induction motors mcqs part1 polyphase induction motors mcqs part2 polyphase induction motors mcqs part3 polyphase induction motors mcqs part4 polyphase induction motors mcqs part5. The torque produced at a given rpm is not constant, but pulsates at twice the line frequency around a median value. Polyphase induction motors mcqs answers pdf electrical engg. Reference mg 1 for specific design letter information based on motor horsepower, speed. Squirrel cage motors are a subclass of induction motors, which harness electromagnetism to generate motion. There is no electrical connection between these bars. The squirrel cage induction motors are 90% used in various industrial, domestic and commercial applications. These bars are shorted at each end with shorting rings.
Construction of squirrel cage induction motor explained. Pdf improving squirrel cage induction motor efficiency. In squirrel cage induction motors, the rotor slots are usually given slight skew in order to. Search wegthreephaseinductionmotorstlinesquirrelcage. 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. Nikola tesla 18561943 invented the polyphase ac induction motor not as a result of intense research, but surprisingly, while on vacation. This rotating magnetic field has a speed which is known as the synchronous speed. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used. The electric energy generated purchased by consumers for different needs. Electromagnetic fields inside induction motors have been studied before the. They are socalled squirrel cage motors because the shape of their rotor the. Introduction this manual provides information on how to safely install, couple to the driven equipment, and maintain the toshiba squirrel cage mediumvoltage induction motor. Rotor induction motor an overview sciencedirect topics. This practice covers motors that are totallyenclosed fancooled ic 411 type, premium efficiency ie3, aircooled, with ip 54 degree of protection for motors and auxiliaries, and with.
Design of a three phase squirrel cage induction motor for. Design of a three phase squirrel cage induction motor for electric propulsion system. On the other hand, the polyphase induction motor shown in cutaway in fig. The motor takes its name from the shape of its rotor windings a ring at either end of the rotor, with. Differentiate between the various types of generating electric power stations. Kanpur, india design of a three phase squirrel cage induction motor for electric propulsion system ravi. The torque produced at a given rpm is not constant.
Realtime polyphase induction motors multiple choice. Wound rotor induction motors ac motors electronics. On the following pages the basic operation and types. Threephase currents flowing within the stator create a rotating magnetic field which induces a current and consequent magnetic field in the rotor. However, should the motor require service, this manual includes a section that assists the. Ac induction motors are also the most common motors used in main powered home appliances. Induction motors are favored due to their ruggedness and simplicity.
Most common ac motors use the squirrel cage rotor, which will be found in virtually all domestic and light industrial alternating current motors. In that period, some estimates surpassed thirty million polyphase induction motors. The squirrel cage motor is the simplest to manufacture and the easiest to maintain. This article presents an understanding of what squirrel cage induction motors are and. We classify starting methods for squirrel cage induction motor into two types on the basis of voltage. Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. Information guide for general purpose industrial ac small and. Nema mg 102001 energy management guide for selection and use of fixed frequency medium ac squirrel cage polyphase induction motors.
Stator and rotor air gap fluxes, the interaction of which produces useful. Tesla polyphase induction motors ac motors electronics textbook. Around 1950, about fifteen million singlephase induction motors were produced annually. Tesla polyphase induction motors ac motors electronics. Learn the working principle and applications of a squirrel cage induction. Pdf noise of polyphase electric motors researchgate. Squirrel cage wound rotor with slip rings the rotating magnetic field. Their sole purpose is to allow resistance to be placed in series with the rotor windings while. Practicing all polyphase induction motors electrical engineering questions and answers in online helps you to improve your ability to attend the real time gate, ies and bsnl jto exams.
Most common ac motors use the squirrelcage rotor, which will be found in virtually all domestic and light industrial alternating current motors. Selfstarting polyphase induction motors produce torque even at standstill. Mostafa elshahed objectives learn a brief history of the electrical power systems construction. Three phase induction motors w60 line squirrel cage rotor horizontal. The reason for the name squirrel cage is because of the type of rotor used in these motors.
Jul 25, 2019 squirrel cage induction motor working principle. Advantages of 3 phase induction motor generally easy to build and cheaper than corresponding dc or synchronous motors induction motor is robust. Most of 3phase induction motors use squirrel cage rotor as it has a remarkably simple and robust construction enabling it. 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. Why the starting torque of squirrel cage induction motor is low. Pdf polyphase induction machines nasrin shaheen academia.
Third international conference on advances in control and optimization of dynamical systems march 15, 2014. There are two general types of polyphase induction motors. Now let us discuss in detail, the most common form of induction motor, the squirrel cage induction motor. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. Information and recommendations for the engineer fe1100. Analysis and design of ac induction motors with squirrel. Latest polyphase induction motors multiple choice questions. 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. Construction of three phase induction motor electrical4u. Recall that leakage reactance is the reactance due to the rotor flux lines that do not also couple with the stator windings. The squirrel cage refers to the rotating exercise cage for pet animals.
Information guide for general purpose industrial ac small. Closedform analysis of squirrelcage induction motors with. In order to choose a starting method for a squirrel cage motor, we have three main considerations. Kanpur, india design of a three phase squirrel cage induction motor for electric propulsion system ravi prakash,mohammad junaidakhtar, r. Squirrelcage rotor almost 90 per cent of induction motors are squirrelcage type, because this type of rotor has the. Control of motorcharacteristics by squirrelcage rotordesign. Squirrel cage induction motor the operation of the squirrel cage motor is. Those induction motors which employ squirrel cage rotor are called squirrel cage induction motors. Advantages of three phase squirrel cage induction motor. Ac motors dc motors permanent magnet series wound shunt wound compound wound singlephase polyphase universal motors induction synchronous induction synchronous squirrel cage wound rotor shaded pole hysteresis reluctance permanent magnet wound rotor squirrel cage splitphase capacitorstart permanent split capacitor capacitor startrun shaded. The squirrelcage motor is the simplest to manufacture and the easiest to maintain. Latest polyphase induction motors multiple choice questions and answers pdf 31.
Polyphase induction motors mcqs answers pdf electrical. 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. The rotor is constructed using a number of single bars shortcircuited by end rings and arranged in a hamsterwheel or squirrel cage configuration. 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. Analysis and design of ac induction motors with squirrel cage rotors.
The squirrel cage induction motor was designed for an extended service life under very demanding. The rotor is constructed using a number of single bars shortcircuited by end rings and arranged in a. The most common type of motor in this group is the squirrelcage polyphase induction motor so called because the rotor is constructed like a squirrelcage fig. Wound rotor induction motors ac motors electronics textbook. It is very commonly used in industries because it is very cheap, robust, efficient, and reliable. For squirrelcage motors this peaktorque slip is relatively small, much as is shown. These induction motors require special attention during its design.
Starting methods for polyphase induction machine electrical4u. Due to the simple rotor construction, the squirrel cage motor is rugged and durable, and is the most common type. In a squirrel cage induction motor, the rotor has conductive bars embedded in slots in the laminations, running the length of the rotor. The most common type of motor in this group is the squirrel cage polyphase induction motor so called because the rotor is constructed like a squirrel cage fig. It is simple and relatively inexpensive, and the absence of sliding contacts in the squirrelcage machine reduces maintenance to a minimum. What is a squirrel cage motor and how does it work. Dual voltage motors polyphase and singlephase motors may be furnished as dual voltage ratings under the following conditions. The majority of commercial and industrial applications usually involve the use of a threephase squirrelcage induction motor. The most common type of motor in this group is the squirrelcage polyphase induction motor so called because the rotor is constructed like a. Pdf the subject of this paper is the control possibility of the multiphase cage. 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. In this method we directly switch the stator of the three phase squirrel cage induction motor on to the supply mains. Class 8736 starters consist of one class 8502 contactor and one class 8536 starter mechanically and electrically interlocked.
For motors falling outside this description, the more comprehensive model specifications below are recommended. Designing of three phase squirrel cage induction motor for. Analysis and design of ac induction motors with squirrel cage. In order to understand the speed control, theory and methods, it is important that the basic theory of the controlled component i. The majority of commercial and industrial applications usually involve the use of a threephase squirrel cage induction motor. Those design letters provide information regarding lockedrotor torque, pullup torque, and slip values at rated torque and are shown in table 8. Pdf speed control of multiphase cage induction motors. The threephase induction motor is the extensively used for various kinds of industrial drives. Squirrelcage induction motor the operation of the squirrelcage motor is. Wegthreephaseinductionmotorstlinesquirrelcagerotor12364818manualenglish. The three phase induction motor is the most widely used electrical motor. Efficiency of polyphase squirrelcage medium motors with continuous ratings nominal efficiency column in table 50 which shall be not greater than the average efficiency of a large population of motors of the same design.
Almost 90 per cent of induction motors are squirrel cage type, because this type of rotor has the simplest and most rugged construction imaginable and is almost indestructible. A wound rotor induction motor has a stator like a squirrel cage induction motor, but a rotor with insulated windings brought out via slip rings and brushes however, no power is applied to the slip rings. A simple explanation of squirrel cage induction motors. Almost 95% of the induction motors used is of squirrel cage type. Nema classes for polyphase squirrel cage induction motors.
A 3 phase ac induction motor photoed by hordu motor. It is low cost and requires low maintenance in comparison with other motor types. Let us consider first squirrel cage type of induction motor. It is simple and relatively inexpensive, and the absence of sliding contacts in the squirrel cage machine reduces maintenance to a minimum. A 3 phase induction motor can be used for different applications with various speed and load requirements.
The efficiency shall be identified on the nameplate by the. The squirrel cage induction motor is the most commonly used motor in industry. Polyphase and singlephase motors may be furnished as dual volt. The squirrelcage refers to the rotating exercise cage for pet animals. This way, designers can make informed choices when choosing the right motor. A polyphase induction motor consists of a polyphase winding embedded in a laminated stator and a conductive squirrel cage embedded in a laminated rotor. Both voltages are standard for the particular rating as listed in tables 1 and 2. What is the difference between a squirrel cage motor and a. The effect of unbalanced voltages on polyphase induction motors is equivalent to the. This method is also known as the dol method for starting the three phase squirrel cage induction motor. Realtime polyphase induction motors multiple choice questions.
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