Before answering the question we have to know about types of rotors in induction motors. The sliptorque curve for deep bar rotor is shown below along with the deep bar stator. The deep and narrow rotor bars have the torquespeed characteristics similar to those of a doublecage rotor. A double cage rotor has essentially two parallel rotor bar circuits built into the rotor. Performance analysis of three phase squirrel cage induction. Designing of three phase squirrel cage induction motor for. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain published on 27 oct 15. Detecting broken rotor bars prevents catastrophic damage. As the name indicates, the double cage induction motors have two cages in the rotor and they have the advantages of both squirrel cage induction motors and wound rotor induction motors. Double cage induction motor introduction diy electrical. Now that you know some of the design characteristics of the double cage rotor, are there any special considerations that should be given for testing. Harley and yao duan georgia institute of technology november, 2009. A wound rotor motor can be used for very severe starting conditions or when speed control by rotor resistance is required. The double cage behaves like a deep bar cage electric equipment.
It is seen that the top most layer element a is linked with minimum leakage flux and therefore its leakage inductance is minimum. The resistance of the upper cage winding is more than the inner c. For the case when skin effect can be neglected in both cages, let us. The electrical machines ii notes pdf em ii pdf notes em ii notes pdf file to download are listed below please check it. Double cage rotor of an induction motor circuit globe. The outer bars consists of rotor bars having low reactance and high resistance.
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. Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque. Due to this reason, the cost of the motor is quite low. Double cage rotor of an induction motor rotor resistance control of an induction motor. May 02, 2016 before answering the question we have to know about types of rotors in induction motors. Circle diagram in three phase induction motor mcqs with an. Threephase induction 208v motor with matlab revised. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. Nov 01, 2004 broken bars cause torque and speed oscillations in the rotor, provoking premature wear of bearings and other driven components.
Both deep bars and double cage structures 123 4 have the same effects. The rotor of of an induction motor can be designed in two types. Some cages enhance the deep bar effect to improve the starting performances. Parameters estimation of squirrelcage induction motors using. The model of doublecage induction motor for the analysis. Motor torque, load torque and selection of motors 243 2. Analytical calculation of equivalent circuit parameters accounting for deep bar effect in multiplecage squirrel cage rotor conference paper pdf available september 2014 with 119 reads. It has been proved that it behaves like a deep bar cage, but it produces even higher starting torque at lower starting current. Enter your email below to receive free informative articles on.
At squirrel cage rotor we can not add external resistance which means speed. This is the reactance due to the rotor flux lines that do not couple with the stator windings. It is similar to the deepbar rotor, except that the difference between lowslip and highslip operation is even more exaggerated. Conventional squirrel cage motors suffer from the disadvantages of low starting torque because of low rotor resistance. Request pdf study of double cage induction motors with different rotor bar. The rotor will constantly be turning to align its magnetic field with that of the stator field.
In operation, the nonrotating stator winding is connected to an alternating current power source. Advantage of double cage rotor over single cage rotor induction motor enesi asizehi yahaya tola omokhafe eugene o. Pdf skin effect modelling in induction motors rotor deep bars. The induction motor rotor is a completely shortcircuited conductive cage. Induction machines using this type of rotor are widespread. Large air pockets in diecast aluminum alloy rotor windings can cause nonuniform bar expansion leading to rotor bending and imbalance that causes high vibration levels from premature bearing wear. Figure 727a shows a current flowing through the upper part of a deep rotor bar.
Pier b online fault prediction of deep bar cage rotor. The figure below shows a deep bar cage rotor with deep and narrow bars. This arrangement is used for obtaining high starting torque at a low value of starting current. Mar 25, 2017 in some applications, very high starting torquetstarttrated. Advantages and disadvantages of induction motor electrical4u. Classes a and b have similar torquespeed characteristics. Electrical machines 2 pdf notes em 2 pdf notes smartzworld. Pdf analytical calculation of equivalent circuit parameters. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol. More emphasis should be put on the acquisition of an inrushstartup test as a baseline. Jul 06, 2017 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. It consists of a large, lowresistance set of bars buried deeply in the rotor and a small, highresistance set of bars set at the rotor surface.
The stator winding poles rotor lamination rotor bar end ring fan fan. The model of double cage induction motor for the analysis of thermal fields in transient operations. The basic concept is illustrated with a deep bar rotor in figure 727. A bar may be assumed to be made up of number of narrow layers as shown in fig. Sep 15, 2017 double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. Based on the influence of the skin effect over electrical rotor parameters can be constructed a mathematical mode. Double cage induction motor electrical engineers guide. Consequently, at high slip frequency, the rotor current resides mainly in the upper starting cage while, at low slip frequency, the current flows mainly into the working lower cage. The double cage rotor has two cages in which rotor winding is accommodated.
Due to the absence of brushes, there are no sparks in the motor. Advantage of double cage rotor over single cage rotor. The squirrel cage with deep rotor bar can be equivalent with a double cage, one of these cages being with constant parameters 8. Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. Double cage rotor of an induction motor 6nq8vq6w61nw idocpub. A squirrel cage induction motor does not contain brushes, slip rings and commutators. Deep bar and double cage rotor design how can a variable rotor resistance be produced to combine the high starting torque and low starting current of class d, with the low normal operating slip and high efficiency of class a use deep rotor bars class b or double cage rotors class c the basic concept is illustrated below. Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. The deep bar rotor has a single cage, usually of copper, formed in slots which are deeper and narrower than in a conventional single cage design. An induction motor model with deepbar effect and leakage.
Control of motor characteristics by squirrel cage rotor design the reactance x2 in the equivalent circuit of an induction motor represents the rotor s leakage reactance. A thermal lumpedparameter model that accurately determines the stator and rotor representative temperatures is proposed and experimentally verified. Thus external resistance could not be added to the rotor circuit. Double cage rotors free download as powerpoint presentation. This includes the starting and running values of the rotor single cage equivalent circuit. In deep bar double cage rotor bars are there in two layers. Slip ring rotor for both of them the stator part connection is same. When the speed of the rotor of the deep bar double cage induction motor increases, the frequency of the induced emf and current in the rotor gets gradually decreased. As the torrent of water dried up for the first time in thousands of years. Squirrel cage rotor wound type rotor or slip ring type rotor squirrel cage rotor in this type. Rotor as the name suggests it is a rotating part of an electrical machine, in which current is induced by transformer action from rotating magnetic field.
Construction of squirrel cage induction motor explained. Home category electrical engineering mcq questions. Dec 26, 2015 in this small post we will discuss about the double cage induction motor in brief. This article presents a way to analyze the skin effect, in the deep bars of induction motors im. Types of starters in three phase induction motor mcqs with. Pdf skin effect modelling in induction motors rotor deep. James federal university of technology, department of electrical and electronics engineering, minna, nigeria pmb 65, minna, niger state abstract.
Pdf the model of doublecage induction motor for the. Double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. These drawbacks are removed by a double squirrel cage motor, which has high starting torque without sacrificing efficiency. Basically the design of electric motor involves the study of the voltages designing of three phase squirrel cage induction motor for good efficiency 1jagdish singh, 2khushdeep singh, 3harleen kaur. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. The attractive qualities of lowcost, ruggedness and maintenancefree operation of the squirrelcage motor has impelled designers to find ways of. A twophase dynamic induction motor model is derived which includes the effects of rotor bar eddy currents and leakage inductance saturation. The double cage behaves like a deep bar cage electric. Vibration signature analysis for rotor broken bar diagnosis. In this small post we will discuss about the double cage induction motor in brief. The paper aims to investigate the use of the finite element method for electrical and mechanical faults detection in threephase squirrel cage, induction machines. Dynamic modelling of induction motor squirrel cage for di. Dynamic modelling of induction motor squirrel cage for. Deepbar cage rotor figure below shows a cage rotor with deep and narrow bars.
Generally in induction motor related operations, squirrel cage induction motors are widely used. Control of motorcharacteristics by squirrel cage rotordesign. Thus both r be and x be vary with slip frequency as they do in a deep bar single cage figure 9. What are the merits and demerits of singlecage and double. As it will be shown in later chapters, both types of electrical conduction are found in turbogenerators. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor.
Nema national electrical manufacturers association class a. The higher valued rotor resistance results more torque to be developed at the starting. Double cage and deep bar squirrel cage rotor induction motor. Deep bar or double cage rotors are used in squirrel cage. One set is deeper closer to the shaft and the other set is commonly smaller and shallower closer to the. The slotting arrangement for double cage induction motor is as shown in above figure. Study of double cage induction motors with different rotor bar.
Deep bar and multiple cage effects are useful in design of such machines. The model is based on approximate analysis of the airgap. Traditional design of cage rotor induction motors ronald g. The stator of a double cage induction motor is similar to that of ordinary induction motor. Figure 4 shows the nema designs and the rotor bar geometries that produce the responses. An induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. At standstill, the rotor current is the same frequency as the stator current, and tends to travel at the outermost parts of the cage rotor bars by skin effect. Brief summary of rotor cage design for large motors. A crosssectional view of a doublecage rotor is shown in figure 725c. It is shown that a useful understanding of how different slot shapes work may be developed through the use of frequency response curves that describe rotor slot impedance as a function of rotor frequency. The invention further relates to a method for producing such a cage rotor.
The invention relates to a cage rotor for an asynchronous machine 1 comprising starting bars for improving the starting behavior. Double cage equivalent of deep bar rotor motor electric. Introduction as stated in prior research l, 2, while starting up the deep bar and double squirrel cage motors with soldered rotors, the squirrel cage winding is the component most vulnerable to damage. However, slip rings are used in wound type induction motor to add external resistance to the rotor winding. Us20120187796a1 us391,147 us2010391147a us2012187796a1 us 20120187796 a1 us20120187796 a1 us 20120187796a1 us 2010391147 a us2010391147 a us 2010391147a us 2012187796 a1 us2012187796 a1 us 2012187796a1 authority us united states prior art keywords operating bars operating bars cage rotor material prior art date 20090819 legal status the legal. 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. A squirrel cage rotor is the rotating part of the common squirrel cage induction motor. Apr 17, 2015 the sliptorque curve for deep bar rotor is shown below along with the deep bar stator. Can any body advise me of a straightforward method of converting these parameters to the resistance and reactance of a double cage induction motor, which has a torque speed curve similar to that of the deep bar machine. One can not even add external resistance for starting of purposes, as the rotor bars are permanently short circuited construction of a squirrel cage rotor is here. The squirrel cage with deep rotor bars can be equivalent with a double cage, one of these cages having constant parameters 8. 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.
Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. Two models of induction machines with two rotor windings, that include magnetising flux saturation, are available at present. Designing squirrel cage rotor slots with high conductivity. The squirrel cage winding in this design consists of two layers of bars shortcircuited by end rings. As the name indicate the double cage induction motor has two winding in rotor. Text books electrical machines ii notes em ii notes pdf em ii pdf. This paper deals with deep bar effect in squirrel cage rotors. Ac motors, heating, induction motors, squirrel cage motors, temperature rise 1. Based on the influence of the skin effect over electrical rotor parameters can be constructed a mathematical model for the asynchronous motor with deep rotor bar, that allows simulation of. Effect of harmonics on performance of three phase induction.
Construction is simpler and therefore cheaper than in a double cage rotor, as shown on the right in fig. Double cage rotor of an induction motor a double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. Current density in im with double cage rotor bars at different. High during starting and low at normal operating speed. The bars in a squirrel cage rotor form parallel paths, joined at their ends by end rings. Deep bar cage rotor figure below shows a cage rotor with deep and narrow bars. In general, the farther away a rotor bar is from the stator, the. It is possible to produce a variable rotor resistance by the use of deep rotor bars or double cage rotors. For the caged rotor of the induction motor, the doublecage model is better than the singlecage model. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain high starting torque. Pdf this article presents a way to analyze the skin effect, in the deep bars of induction motors im. Control of motorcharacteristics by squirrelcage rotordesign.
The different bar shapes can give usefully different speedtorque characteristics as well as some control over the inrush current at startup. In a slip ring induction motor, the rotor resistance is a. Deep bar rotor the deep bar rotor in an induction motor is used to obtain high rotor resistance at starting and low rotor resistance at the running condition. Select current density in rotor bars and end rings depends on ambient temp, cooling conditions, and duty cycle, and from rotor bar and end ring currents get their cross sectional areas. Three phase squire cage induction motor, fully enclosed. Double cage rotor a rotor design, which though more expensive gives still better starting, and running performances than the deep bar design, is the double cage rotor.
517 1366 1012 1309 964 1361 217 1637 691 826 29 802 769 1381 301 627 1545 1425 986 1422 988 1646 808 249 581 527 1448 724 1108 878 318 192 887 566 874