The rotor of the motor consists the cylindrical laminated core having semiclosed circular slots and short circuit at each end by copper or aluminium ring, called short circuiting ring. In simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. At starting the 3 phase windings are connected to a star connected rheostat and during the running condition, the windings are shortcircuited at the slip rings. And in the previous article on types of electrical motors, we have classified induction motors based on the type of rotor used. It also involves its switchgears to control its starting inrush current, starting torque, or both, and its overload and shortcircuit protection. Rotor the rotor need not receive external power or excitation other than from the stator. Squireel cage induction motors are widely used in industries. Compared to the squirrel cage rotor, the rotor construction is not simple. The laminations are aligned and heatshrunk onto the shaft, and then the molten aluminum is forced into the slots to form the squirrel cage. Please have a look at the below figures of squirrel cage induction and wound rotor slip ring induction motor. Three phase induction motor construction electrical academia.
Cylindrical laminated core rotor is wound like winding on the stator. The construction of stator of the induction motor is almost the same as other motors. It provides knowledge for industrial engineers, who use motor current signature analysis mcsa to determine if there are any cage winding breaks in their squirrel cage. The squirrel cage induction motor is by far the most common type of induction motor. Control of motorcharacteristics by squirrelcage rotordesign. Improving squirrel cage induction motor efficiency. There are other types of rotors used in ac motors such as synchronous and wound rotor, however, the focus here will be on the squirrel cage.
In squirrel cage induction motors, rotor windings wound in squirrel cage. A highspeed squirrelcage induction machine requires a totally. Rotor material selection and construction topology influence on the electrical machine design are discussed. The sinusoidally distributed flux density wave is moving at slip speed inducing in the rotor cage voltages of magnitude indicated by the blue vertical lines. Analysis and design of ac induction motors with squirrel cage rotors. So s1f1s2f2, and at starting the slip is equal to 1, so a unique value of. Construction of squirrel cage induction motor explained. The squirrel cage induction motors are 90% used in various industrial, domestic and commercial applications. In the project has been done an analysis of the mathematical equations of the whole system.
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. In the slip ring type,the rotor consists of three phase winding similar to that of the stator winding. Squirrel cage rotor type, which comprises a set of copper or aluminum bars installed into the slots, which are connected to an endring at each end of the rotor. Almost 95% of the induction motors used is of squirrel cage type. This simple and rugged construction makes it the favorite for most applications. A squirrelcage induction motor is one in which the secondary circuit consists of a squirrelcage winding suitably disposed in slots in the secondary core. It provides knowledge for industrial engineers, who use motor current signature analysis mcsa to determine if there are any cage winding breaks in their squirrel cage induction motors scims. Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. The construction of stator for any induction motor is almost the same. Difference between squirrel cage and slip ring induction motor.
Industrial application and case histories, first edition. When voltage is applied to the stator winding, a rotating magnetic field is established. The bars are permanently shorted at both the ends with the help of conducting rings called end rings. But the rotor construction differs with respect to the type of motor. Design of a three phase squirrel cage induction motor for. Pdf squirrel cage rotor design and manufacturing for. Dont worry, difference between squirrel cage and slip ring type induction motor is tabulated after the figure. In an induction motor, the electric current in the rotor needed to produce torque is obtained via electromagnetic induction from the rotating magnetic field of the stator winding. Know about the most popular and almost unbreakable construction of squirrel cage induction motor. Squirrel cage and wound rotor or slip rig induction motor.
Select number of stator slots and suitable three phase winding layout. There are mainly two types of induction motor on the basis of power supply, single phase induction motor and three phase induction motor. Design, construction, and manufacture of squirrel cage. As soon as this torque starts to revolve the rotor, additional torque is produced by singlephase inductionmotor action. Basically, it is the construction of rotor which makes squirrel cage induction motor different from wound type induction motor. A squirrelcage rotor is the rotating part of the common squirrel cage induction motor. Veinott, theory and design of small induction motors, new york. The squirrel cage rotor consists of laminated steel in the core with evenly spaced bars of copper or aluminum placed axially around the periphery, permanently shorted at the ends by the end rings. Current signature analysis for condition monitoring of cage induction motors.
Those induction motors which employ squirrel cage rotor are called squirrel cage induction motors. A highspeed squirrel cage induction machine requires a totally different design compared to the traditional squirrel cage industrial motor because of the mechanical limitations caused by the high speed. The induction motor are of two types based on the construction of rotor. However, should the motor require service, this manual includes a section that assists the. In this article, we will learn about squirrel cage and slip ring induction motors. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. The rotor consists of a cylindrical lamina ted core with parallel slots for carrying the rotor conductors which, it should be. Starting torque is directly proportional to the rotor resistance. Examine the construction of the squirrel cage induction motor module ems 8221, paying particulat attention to the motor, connection terminals and the wiring 2. How are high starting torques obtained in a squirrel cage. Because of the large rotor resistance, this motor has a pullout torque occurring at a high slip, and its starting torque is quite high.
Select specific electric loading ac ampere conductors per meter of air gap circumference from. Advantages and disadvantages of squirrel cage induction motor. However, it suffers from the disadvantage of a low starting torque. The rotor is of the squirrel cage type and is under the influence of this moving field.
Know about the different winding slots, lamination of the stator and its construction. Its torquespeed characteristic is also shown in figure 726. Modeling and control of squirrel cage induction generator. Design, construction, and manufacture of squirrel cage rotors.
Cage rotors are cast or fabricated of aluminum, copper, or other metals. An induction motor also known as an asynchronous motor is a commonly used ac electric motor. The rotor cage is similar in appearance to pet rodent exercise wheels from over a century ago, thus the name squirrel cage. Third international conference on advances in control and optimization of dynamical systems march 15, 2014. Induction motor construction squirrel cage rotor duration.
Squirrel cage rotor design and manufacturing for highspeed applications article pdf available in ieee transactions on industrial electronics pp99. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Squirrel cage induction rotor winding failure mechanisms. Pdf squirrel cage rotor design and manufacturing for high. Their susceptibility to failure is dependent on the type of winding construction, the motor application, operating duty, winding geometry, and the materials of construction.
The rotor is built of a stack of steel laminations, such as the one shown in figure 3. The rotor is constructed using a number of single bars shortcircuited by end rings and arranged in a hamsterwheel or squirrelcage configuration. Parida department of electrical engineering national institute of technology, silchar,assam, india email. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. Based on the rotor construction, 3 phase induction motor can be of two types. 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. Aluminum rotor bars are usually diecast into the rotor slots, which results in a very rugged construction. In operation, the nonrotating stator winding is connected to an alternating current power source. In the induction motors used in lift and hoists, you will see a type of rotor called a slip ring rotor, whereas in most of the other applications you will see a simpler, squirrel cage type of rotor. The following are common methods to start a squirrel cage motor, depending upon the limitation, if.
The starting torque of the squirrelcage rotor can be increased by shaping the rotor bars. Keeping the vf ratio constant, when frequency is reduced then that results in constant slipfrequency at running. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents. Horizontal squirrel cage mediumvoltage induction motor. Designing of three phase squirrel cage induction motor for. Several text books show how to compute rotor bar and end ring currents, resistances. Squirrel cage induction motor is used in lathes, drilling machine, fan, blower printing machines etc. The motor accelerates to a speed slightly below the synchronous speed and runs as a. Electrical interview questions which motor is best. Kanpur, india design of a three phase squirrel cage induction motor for electric propulsion system ravi prakash,mohammad junaidakhtar, r.
Squirrel cage induction motor the engineering projects. This results in a more complicated rotor construction and expensive material selection, and sets higher standards for the manufacturing precision. How are squirrel cage induction motors constructed. 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. Most of single phase induction motors use squirrel cage rotor as it has a remarkably simple and robust construction enabling it to operate in the most adverse circumstances. The figure itself depicts many difference between the two types of motors. 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. The starting of an induction motor does not relate to simple switching alone. Pdf design and fabrication of high efficiency squirrel cage. A squirrelcage motor with this type of rotor construction is called. The entire structure looks like cage hence it is called a squirrel cage rotor. Squirrelcage rotor design and manufacturing for highspeed. These motors are very robust in construction and very cheap.
The construction of the rotor is rugged and simple. This rotor consists of uninsulated copper or aluminium bars, placed in the slots. Consequently, a small starting torque is developed. This results in a more complicated rotor construction and expensive. Traditional design of cage rotor induction motors publish. This chapter presents the essential features of the design, construction, and manufacture of squirrel cage induction rotors. These motors are having the difference in rotor construction. The rotating magnetizing field represented by the space vector b m or, equivalently by the magnetizing current i m moves at the synchronous speed. The construction of these rotor windings resembles a squirrel cage. Almost 70% of the industrial motors and drives comes under these category. What is the difference between a slip ring and a squirrel.
A identify the stator windings note that they consist of many tuns of small diameter wize evenly spaced axound the stator. According to the labelled notation a represents stator b rotor c bearing shields d fan e ventilation grill and f terminal box. Pdf improving squirrel cage induction motor efficiency. Squirrelcage rotor design and manufacturing for high. Closedform analysis of squirrelcage induction motors with. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. Squirrelcage rotor almost 90 per cent of induction motors are squirrelcage type, because this type of rotor has the simplest and most rugged construction imaginable and is almost indestructible. Also appreciate the rugged construction of squirrel cage rotor and know the spectacular reasons for the skewed arrangements of the rotor conductors. Three phase squire cage induction motor, fully enclosed. Shaded pole induction motors working and construction. The motor which employing squirrel cage type rotor is known as the squirrel cage motor. Basic construction of 3phase ac induction motors you.
A squirrel cage motor with this type of rotor construction is called nemadesign class d. Using variable voltage variable frequency vvvf drive. As there are no brushes and slip ring, these motors requires less maintenance. The rotor of an induction motor can be a squirrel cage rotor or wound type rotor. But the rotor construction differs with respect to the type which is specified above. 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. Control of motor characteristics by squirrelcage rotor design. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Standard handbook of petroleum and natural gas engineering third edition, 2016.
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