The reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance. The rotor is not power supplied externally and the currents that flow through it are induced. Horizontal squirrel cage mediumvoltage induction motor. A generalized two axes model of a squirrel cage induction motor is developed. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents. Slip ring induction motor fundamentals pnpntransistor. The induction motor are of two types based on the construction of rotor. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. Reaction of a squirrelcage rotor in a 2pole field in the rotor reference frame.
Analysis and design of ac induction motors with squirrel cage. These motors are very robust in construction and very cheap. 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. The rotor of the motor can be braked to stop at a predetermined. Massachusetts institute of technology cambridge, massachusetts, 029, usa tel. A generalized two axes model of a squirrelcage induction motor for rotor fault diagnosis samir hamdani1, omar touhami2, rachid ibtiouen2 abstract. Analysis and design of ac induction motors with squirrel. 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. The main reason for connecting the armature coils through slip rings rather than connecting them directly is to allow insertion of a variable resistor into the. Older units were cast from copper, though that technique is rarely used today. Please have a look at the below figures of squirrel cage induction and wound rotor slip ring induction motor. A squirrelcage rotor is the rotating part of the common squirrel cage induction motor.
Although the emphasis in this work has been placed on the threephase induction motor with a squirrel cage rotor, the same modelling approaches hold for the. In this approach, the direct connection from geometry to performance is suppressed. This paper describes an investigation into ways of taking advantage of the higher. Analysis and design of ac induction motors with squirrel cage rotors by shine ho university of new hampshire, september, 1996 the traditional approach to modelling the ac induction motor revolves around the wellknown equivalent t circuit model. Squirrel cage rotor 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.
Pdf this paper deals with the optimal design of squirrel cage rotor slots and copper bars of high power induction motors with respect to the values. Squirrelcage rotor options for ac induction motors request pdf. It is called a squirrel cage motor because the rotor inside of it known as a squirrel cage rotor looks like a squirrel cage. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. The rotor is separated from the stator by a small airgap which ranges from 0. Hz, operating voltage 415 volts, squirrel cage rotor type, starting stardelta, efficiency 0. 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 general construction of the slots in the rotor is such that the rotor bars are placed close to the surface so as to reduce the reactance. Squirrel cage induction motor provides low starting torque. Modeling and control of squirrel cage induction generator. Due to shortcircuiting of bars through end rings, rotor terminals are not accessible to the user. An anisotropic homogeneous representation for both squirrelcage rotor and stator windings is used. When a 3 phase supply is given to the stator winding it sets up a rotating magnetic field in space. We saw the construction of the squirrel cage induction motor. Information guide for general purpose industrial ac small and medium squirrelcage induction motor standards. The rotor of a threephase squirrel cage induction motor consists of a set of noninsulated bars that are interconnected by shortcircuit rings. 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. Difference between squirrel cage and slip ring induction motor. However, should the motor require service, this manual includes a section that assists the. Designing squirrel cage rotor slots with high conductivity james l.
A generalized two axes model of a squirrel cage induction motor for rotor fault diagnosis samir hamdani1, omar touhami2, rachid ibtiouen2 abstract. This rotor is a cylinder of steel laminations, with highly. The most popular squirrel cage induction motor is of a 4pole design. Know about the most popular and almost unbreakable construction of squirrel cage induction motor. Information guide for general purpose industrial ac small and. There has been, in recent years, an effort to make cast copper rotors for industrial use induction motors. Also a provision can be made in the switching device to avoid the condition of an open transient during the changeover from y to d as discussed in section 4. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm. Squirrel cage induction motor an overview sciencedirect. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Squirrel cage rotor construction can be stated as follows lamination or motor core material are stacked in cylindrical shape, metal bars are placed in to this lamination slots perpendicularly. Know about the different winding slots, lamination of the stator and its construction.
While aluminum rotors may be diecast, copper models are made using individual components assembled by hand. In a squirrel cage induction motor, the rotor has conductive bars embedded in slots in the laminations, running the length of the rotor. A generalized two axes model of a squirrelcage induction motor is developed. The construction of the rotor is rugged and simple. As its name indicates stator is a stationary part of induction motor. Almost 70% of the industrial motors and drives comes under these category. They are inherently speed regulating machines, this being achieved by adding resistance to the rotor circuit via the slip rings. This model is based on a winding function approach and the coupled. Also lets get to know the methods which are used to control the speed of squirrel cage. The rotor consists of a cylindrical lamina ted core with parallel slots for carrying the rotor conductors which, it should be. Dont worry, difference between squirrel cage and slip ring type induction motor is tabulated after the figure. Also appreciate the rugged construction of squirrel cage rotor and know the spectacular reasons for the skewed arrangements of the rotor conductors. A squirrel cage rotor has a laminated iron core with slots for placing skewed conductors, which may be a copper, aluminum, or alloy bar.
Starting of squirrel cage induction motors487 delta at a higher cost to the insulation system which may also call for a larger frame size. Closedform analysis of squirrelcage induction motors with. Construction of squirrel cage induction motor explained. The standards in this guide cover alternatingcurrent squirrel cage motors up to and including the ratings built in frames corresponding to the continuous opentype ratings given in table 1. What is the difference between a slip ring and a squirrel. These machines are different from the squirrel cage induction motor in that the rotor is wound, and the end of the windings brought out to slip rings.
Information guide for general purpose industrial ac small. Lecture 6 three phase induction motors cairo university. In simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. The figure itself depicts many difference between the two types of motors. This rotor is made up from parallel aluminum or copper bars.
Pdf a highspeed squirrelcage induction machine requires totally different design compared to the traditional squirrel cage industrial motor. Designing of three phase squirrel cage induction motor for. Wound rotor induction motors ac motors electronics. Stator is made up of number of stampings in which different slots are. Threephase asynchronous motors with squirrelcage rotor for low voltage applications. Pdf squirrel cage rotor design and manufacturing for high. Wound rotor induction motors ac motors electronics textbook. The rotating magnetizing field represented by the space vector b m or, equivalently by the magnetizing current i m moves at the synchronous speed. Squirrel cage induction motor the engineering projects. Working of double squirrel cage motor at starting of the motor, frequency of induced emf is high because of large slip slip frequency of rotor emf supply frequency. 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 electric motor type the rotor is constituted by a series of bars arranged in the grooves of the rotor crown, joined at their ends to two rings. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface.
Three phase squire cage induction motor, fully enclosed. 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. The motor which employing squirrel cage type rotor is known as the squirrel cage motor. The starting torque is small and the intensity they absorb is high. This regulation specifies the eco design requirements for 2, 4 and 6pole lowvoltage threephase asynchronous motors in the output range from 0. Cage induction machines institut fur elektrische energiewandlung. In squirrel cage induction motors, rotor windings wound in squirrel cage. Design procedure design procedure consists of the following steps.
This type of rotor consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Pdf three phase squirrel cage induction motor, conctruction. A rotor also composed of punched laminations, with rotor slots for the rotor winding. Standard types of squirrel cage motors the three phase squirrel cage induction motors are classified into 6 different standard types based on their electrical characteristics. Recall that leakage reactance is the reactance due to the rotor flux lines that do not also couple with the stator windings. 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 induction rotor. The rotor will constantly be turning to align its magnetic field. Advantages and disadvantages of squirrel cage induction motor. M is totally different from the squirrel cage rotor. Squireel cage induction motors are widely used in industries. The heat generated during starting is mostly dissipated external to the motor in the starting resistance.
The 3phase set of currents, each of equal magnitude and with a phase difference of 120o, flow in the stator windings and generate a rotating. 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. Squirrel cage rotor design and manufacturing for highspeed applications article pdf available in ieee transactions on industrial electronics pp99. Squirrelcage rotor options for ac induction motors. A shorted rotor operates like a squirrel cage rotor. We can able to add external resistance through slip ring in the rotor circuit. 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.
The bars and the end rings together look like a cage and hence such a rotor is called cage rotor or squirrel, cage rotor. In the slip ring type,the rotor consists of three phase winding similar to that of the stator winding. May 18, 2018 please have a look at the below figures of squirrel cage induction and wound rotor slip ring induction motor. Starting torque is directly proportional to the rotor resistance.
In operation, the nonrotating stator winding is connected to an alternating current power source. A squirrel cage motor comprises a stator and a rotor, the latter having a pair of end rings and conductor bars interconnecting the end rings, the bars and rings being supported on the rotor core. Installation, operating and maintenance instructions three. Basically, it is the construction of rotor which makes squirrel cage induction motor different from wound type induction motor. Low and high voltage three phase induction motors m line squirrel cage rotor horizontal date. The stator winding poles rotor lamination rotor bar end ring fan fan. How are squirrel cage induction motors constructed. These rotor bars are shortcircuited at both ends through end rings as shown in fig. Their sole purpose is to allow resistance to be placed in series with the rotor windings while starting figure below. These bars are shorted at each end with shorting rings. Most of the manufactured motors are of the squirrelcage type. Design of a three phase squirrel cage induction motor for electric.
This squirrel cage motor because the rotor rotating field induces currents in the inside of it known as a squirrel cage rotor by electromagnetic induction. This paper describes an investigation into ways of taking advantage of the higher conductivity of cast copper in rotors of induction motors. Each squirrelcage rotor must be carefully constructed to meet the demands of different types of applications. Designing squirrel cage rotor slots with high conductivity.
The bars in a squirrel cage rotor form parallel paths, joined at their ends by end rings. Analysis and design of ac induction motors with squirrel cage rotors. Control of motorcharacteristics by squirrelcage rotordesign the reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance. There is a wide variety of design options available depending upon the motor size and application.
Pdf squirrel cage rotor design and manufacturing for. The squirrel cage induction motor was designed for an extended service life under very demanding conditions. A generalized two axes model of a squirrelcage induction. To overcome this disadvantages of squirrel cage slip ring induction motor is used. These motors can be started at a fullload while developing normal starting torque. Control of motorcharacteristics by squirrelcage rotordesign. Pdf optimal design of rotor slot geometry of squirrel.
Threephase induction motor squirrel cage rotor customer. The main difference between slip ring and squirrel cage induction motor is the rotor construction. The squirrel cage motor is a type of asynchronous motor. Control of motor characteristics by squirrelcage rotor design. The squirrelcage 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. Oct 09, 2016 in simple words, the type of 3 phase induction motor which uses a squirrel cage rotor is called squirrel cage induction motor. According to the national electrical manufacturers association nema, one differentiates between the classes a, b, c, and d as is indicated in the torquespeed characteristics of fig. Search wegthreephaseinductionmotorstlinesquirrelcage.
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