Advantage of double cage rotor over single cage rotor. Double cage induction motor introduction diy electrical. In operation, the nonrotating stator winding is connected to an alternating current power source. 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. 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. Circle diagram in three phase induction motor mcqs with an. Classes a and b have similar torquespeed characteristics.
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. The slotting arrangement for double cage induction motor is as shown in above figure. At squirrel cage rotor we can not add external resistance which means speed. 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. Mar 25, 2017 in some applications, very high starting torquetstarttrated. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain high starting torque. The different bar shapes can give usefully different speedtorque characteristics as well as some control over the inrush current at startup. Due to the absence of brushes, there are no sparks in the motor. Squirrel cage rotor wound type rotor or slip ring type rotor squirrel cage rotor in this type. 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 model of double cage induction motor for the analysis of thermal fields in transient operations. 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. Dynamic modelling of induction motor squirrel cage for di. Three phase squire cage induction motor, fully enclosed. A wound rotor motor can be used for very severe starting conditions or when speed control by rotor resistance is required. Nema national electrical manufacturers association class a. Detecting broken rotor bars prevents catastrophic damage. In a slip ring induction motor, the rotor resistance is a. A thermal lumpedparameter model that accurately determines the stator and rotor representative temperatures is proposed and experimentally verified. Designing squirrel cage rotor slots with high conductivity. A squirrel cage rotor is the rotating part of the common squirrel cage induction motor. Deepbar cage rotor figure below shows a cage rotor with deep and narrow bars. 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 figure below shows a deep bar cage rotor with deep and narrow bars. 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. Dynamic modelling of induction motor squirrel cage for. 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. A bar may be assumed to be made up of number of narrow layers as shown in fig. Generally in induction motor related operations, squirrel cage induction motors are widely used. We have already discussed that the rotor which is of squirrel cage type has two end rings, which are permanently shorted with the rotor conductors. Effect of harmonics on performance of three phase induction. An induction motor model with deepbar effect and leakage. Deep bar cage rotor figure below shows a cage rotor with deep and narrow bars. Control of motorcharacteristics by squirrel cage rotordesign.
More emphasis should be put on the acquisition of an inrushstartup test as a baseline. Thermal and deep bar skin effect models have been created that can be used together for parameter estimation in a vector control application. The induction motor rotor is a completely shortcircuited conductive cage. The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. The stator of a double cage induction motor is similar to that of ordinary induction motor. Construction of squirrel cage induction motor explained. Deep bar and multiple cage effects are useful in design of such machines. It is seen that the top most layer element a is linked with minimum leakage flux and therefore its leakage inductance is minimum. 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.
This is the reactance due to the rotor flux lines that do not couple with the stator windings. 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. Parameters estimation of squirrelcage induction motors using. The paper aims to investigate the use of the finite element method for electrical and mechanical faults detection in threephase squirrel cage, induction machines.
High during starting and low at normal operating speed. The attractive qualities of lowcost, ruggedness and maintenancefree operation of the squirrelcage motor has impelled designers to find ways of. A double cage rotor has essentially two parallel rotor bar circuits built into the rotor. A twophase dynamic induction motor model is derived which includes the effects of rotor bar eddy currents and leakage inductance saturation. A crosssectional view of a doublecage rotor is shown in figure 725c. The stator winding poles rotor lamination rotor bar end ring fan fan.
Advantage of double cage rotor over single cage rotor induction motor enesi asizehi yahaya tola omokhafe eugene o. Pdf analytical calculation of equivalent circuit parameters. The electrical machines ii notes pdf em ii pdf notes em ii notes pdf file to download are listed below please check it. 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. As the torrent of water dried up for the first time in thousands of years. Pier b online fault prediction of deep bar cage rotor. Designing of three phase squirrel cage induction motor for. Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. Home category electrical engineering mcq questions. Current density in im with double cage rotor bars at different. Text books electrical machines ii notes em ii notes pdf em ii pdf. 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.
Brief summary of rotor cage design for large motors. Pdf skin effect modelling in induction motors rotor deep. It is possible to produce a variable rotor resistance by the use of deep rotor bars or double cage rotors. The invention further relates to a method for producing such a cage rotor. Nov 01, 2004 broken bars cause torque and speed oscillations in the rotor, provoking premature wear of bearings and other driven components. 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. Pdf the model of doublecage induction motor for the. Double cage rotor of an induction motor rotor resistance control of an induction motor. The rotor of of an induction motor can be designed in two types. In general, the farther away a rotor bar is from the stator, the. The higher valued rotor resistance results more torque to be developed at the starting.
The resistance of the upper cage winding is more than the inner c. A squirrel cage induction motor does not contain brushes, slip rings and commutators. 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. Slip ring rotor for both of them the stator part connection is same. Two models of induction machines with two rotor windings, that include magnetising flux saturation, are available at present. Double cage rotors free download as powerpoint presentation. Both deep bars and double cage structures 123 4 have the same effects.
The squirrel cage winding in this design consists of two layers of bars shortcircuited by end rings. 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. 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. 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. Harley and yao duan georgia institute of technology november, 2009.
Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque. Based on the influence of the skin effect over electrical rotor parameters can be constructed a mathematical mode. 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. Electrical machines 2 pdf notes em 2 pdf notes smartzworld. These drawbacks are removed by a double squirrel cage motor, which has high starting torque without sacrificing efficiency.
However, slip rings are used in wound type induction motor to add external resistance to the rotor winding. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. 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. What is a double cage rotor, part 2 in the january 5, 2010 tip we discussed what a double cage rotor is. Thus external resistance could not be added to the rotor circuit. What are the merits and demerits of singlecage and double. Before answering the question we have to know about types of rotors in induction motors.
In this small post we will discuss about the double cage induction motor in brief. 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. Ac motors, heating, induction motors, squirrel cage motors, temperature rise 1. Figure 727a shows a current flowing through the upper part of a deep rotor bar. This arrangement is used for obtaining high starting torque at a low value of starting current. Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. 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. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol. Double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. 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. This paper deals with deep bar effect in squirrel cage rotors. This article presents a way to analyze the skin effect, in the deep bars of induction motors im.
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. Some cages enhance the deep bar effect to improve the starting performances. The outer bars consists of rotor bars having low reactance and high resistance. Pdf skin effect modelling in induction motors rotor deep bars. Construction is simpler and therefore cheaper than in a double cage rotor, as shown on the right in fig. The double cage rotor has two cages in which rotor winding is accommodated. The sliptorque curve for deep bar rotor is shown below along with the deep bar stator. 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. An induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Conventional squirrel cage motors suffer from the disadvantages of low starting torque because of low rotor resistance.
Types of starters in three phase induction motor mcqs with. The deep and narrow rotor bars have the torquespeed characteristics similar to those of a doublecage rotor. Motor torque, load torque and selection of motors 243 2. For the case when skin effect can be neglected in both cages, let us.
This includes the starting and running values of the rotor single cage equivalent circuit. Due to this reason, the cost of the motor is quite low. In deep bar double cage rotor bars are there in two layers. It is similar to the deepbar rotor, except that the difference between lowslip and highslip operation is even more exaggerated. The rotor will constantly be turning to align its magnetic field with that of the stator field. Vibration signature analysis for rotor broken bar diagnosis. In this paper, a new diagnostic index that allows the extraction of rotor fault components issued from axial vibration signals, is defined to improve the fault quantification procedure. Traditional design of cage rotor induction motors ronald g.
As it will be shown in later chapters, both types of electrical conduction are found in turbogenerators. Apr 17, 2015 the sliptorque curve for deep bar rotor is shown below along with the deep bar stator. Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. Thus both r be and x be vary with slip frequency as they do in a deep bar single cage figure 9. In pdmas january 5 tip, the company discussed what a doublecage rotor is. The invention relates to a cage rotor for an asynchronous machine 1 comprising starting bars for improving the starting behavior.
One set is deeper closer to the shaft and the other set is commonly smaller and shallower closer to the. Figure 4 shows the nema designs and the rotor bar geometries that produce the responses. The model is based on approximate analysis of the airgap. The basic concept is illustrated with a deep bar rotor in figure 727. The double cage behaves like a deep bar cage electric. For the caged rotor of the induction motor, the doublecage model is better than the singlecage model. Study of double cage induction motors with different rotor bar. Double cage and deep bar squirrel cage rotor induction motor. The bars in a squirrel cage rotor form parallel paths, joined at their ends by end rings. As the name indicate the double cage induction motor has two winding in rotor. Deep bar or double cage rotors are used in squirrel cage. 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. Performance analysis of three phase squirrel cage induction.
Advantages and disadvantages of induction motor electrical4u. Double cage rotor of an induction motor 6nq8vq6w61nw idocpub. 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. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. 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. Dec 26, 2015 in this small post we will discuss about the double cage induction motor in brief. Double cage induction motor electrical engineers guide. The squirrel cage with deep rotor bar can be equivalent with a double cage, one of these cages being with constant parameters 8. Threephase induction 208v motor with matlab revised. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain published on 27 oct 15. Induction machines using this type of rotor are widespread. Control of motorcharacteristics by squirrelcage rotordesign.
Request pdf study of double cage induction motors with different rotor bar. The model of doublecage induction motor for the analysis. James federal university of technology, department of electrical and electronics engineering, minna, nigeria pmb 65, minna, niger state abstract. Double cage rotor of an induction motor circuit globe.
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