Dynamic modeling of double cage induction machines for. In addition, the upper cage is made up of a higher resistance material than the lower cage. Deep bar visavis double cage rotor design for large mv motors. An induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. Expressing torque in per unit of the fullload torque, find a. The slotting arrangement for double cage induction motor is as shown in above figure.
Pdf the model of doublecage induction motor for the analysis of. James federal university of technology, department of electrical and electronics engineering, minna, nigeria pmb 65, minna, niger state abstract. An induction motor or asynchronous motor is an ac electric motor in which the electric current in the rotor needed to produce torque is obtained by electromagnetic induction from the magnetic field of the stator winding. Construction of squirrel cage induction motor explained. The stator and rotor fields interact to produce a rotational torque on the rotor. Three phase squire cage induction motor, fully enclosed. Rotor of a double squirrel cage motor has two independent cages on the same rotor. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents.
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. Application note low inrush current motors help to reduce disturbances to weak supply networks induction motors are used in a wide range of applications, and most are connected directonline. Double cage motor essentially has two sets of bars one of high resistance and the other of low resistance unlike the single cage which has only a low resistance bar. In pdmas january 5 tip, the company discussed what a doublecage rotor is. Ac motors, heating, induction motors, squirrel cage motors, temperature rise 1.
Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. Home category electrical engineering mcq questions. Traditional design of cage rotor induction motors publish. Double cage rotors are still found to some extent today. For single cage model estimation both methods lead to parameter values with deviation less than 1%. Ankaya 2 1department of mechatronics, faculty of engineering and natural sciences, gaziosmanpa. March 2011 converting woundrotor motors to squirrelcage. Study of double cage induction motors with different rotor bar materials. Slip ring rotor for both of them the stator part connection is same.
The rotor of of an induction motor can be designed in two types. Harley and yao duan georgia institute of technology november, 2009. Thus, the starting torque is relatively higher and the starting current is relatively. If the rotor rotated at synchronous speed, the stator flux would not induce a current in the rotor winding, so there would be no torque. Apr 17, 2015 the sliptorque curve for deep bar rotor is shown below along with the deep bar stator. The rotor current frequency is the difference between the rotor speed and the stator rotating magnetic field.
Deep bar or double cage rotors are used in squirrel cage. This is the reactance due to the rotor flux lines that do not couple with the stator windings. Conventional squirrel cage motors suffer from the disadvantages of low starting torque because of low rotor resistance. The double cage behaves like a deep bar cage electric equipment. An induction motors rotor can be either wound type or squirrel cage type. Possible to obtain medium starting torque by using double cage rotor or deep bar rotor viii. If an induction machine with closed or skewed rotor slots is studied, the model for saturation should be extended. Cage rotor 211 double cage rotors 2 deep bar rotors 214 starting and runup of slipring motors 215 influence of supply voltage on torquespeed curve 217 generating and braking 218. At high slips starting conditions the reactances are large. This makes the starting outer cage susceptible to fatigue failure since it must withstand the large thermomechanical stress associated with the high starting current and long acceleration time. Squirrel cage rotor wound type rotor or slip ring type rotor squirrel cage rotor in this type. As stated in prior research l, 2, while starting up the deepbar and doublesquirrelcage. The squirrel cage with deep rotor bar can be equivalent with a double cage, one of these cages being with constant parameters 8. 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.
Since the effective cross section is lower, the rotor resistance is higher. Control of motor characteristics by squirrelcage rotor design. Another phenomenon that is usually omitted within the smallsignal analysis is the skin effect of rotor bars. This article presents a way to analyze the skin effect, in the deep bars of. 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. Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. During the normal operation most of the current flows in the inner cage, called work cage fig. Figure 4 shows the nema designs and the rotor bar geometries that produce the responses. The outer bars consists of rotor bars having low reactance and high resistance. It has been proved that it behaves like a deep bar cage, but it produces even higher starting torque at lower starting current.
Pdf fault prediction of deep bar cage rotor induction motor based. 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. The stator of a double cage induction motor is similar to that of ordinary induction motor. The higher valued rotor resistance results more torque to be developed at the starting. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain published on 27 oct 15.
Traditional design of cage rotor induction motors ronald g. Threephase induction 208v motor with matlab revised. 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. A possible alternative is either a high resistance bar or double cage rotor design.
This arrangement is used for obtaining high starting torque at a low value of starting current. Jan 05, 2016 as explained in chapter 6, the double cage rotor or the deep bar rotor combines the merits of both high and lowresistance rotors by having an outer cage with high resistance and relatively low reactance, in which most of the mains frequency starting current xows, and an inner cage of relatively low resistance and high reactance. Double cage motors double cage rotor asynchronous induction motors for cementmill drive fortherawandcementballmilltwindrivesslipring. Therefore the motor produces higher starting torque. This outer winding has relatively large resistance. The model is based on approximate analysis of the airgap. The electrical machines ii notes pdf em ii pdf notes em ii notes pdf file to download are listed below please check it. Ganz first in the world successfully broke this tradition with double squirrel cage motors supplied to dunadrava cement company at beremend. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain high starting torque. In this small post we will discuss about the double cage induction motor in brief. In deep bar double cage rotor bars are there in two layers. Eindhoven university of technology master modelling and. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. It is seen that the top most layer element a is linked with minimum leakage flux and therefore its leakage inductance is minimum.
It consists of two cages to exaggerate its variation more than the deep bar. Both deep bars and double cage structures 123 4 have the same effects. Pdf electric machines by dp kothari and ij nagrath pdf. 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. Pdf skin effect modelling in induction motors rotor deep bars. In the double cage rotor of an induction motor, there are two layers of the bars. This new solution is significantly cheaper also from the investment side compared to the traditional solutions. 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.
The resistance of the upper cage winding is more than the inner cage winding. Squirrel cage induction motor slip ring induction motor advantages. How a doubly fed induction generator be modelled using a. Double cage rotor of an induction motor 6nq8vq6w61nw idocpub. The squirrel cage with deep rotor bars can be equivalent with a double cage, one of these cages having constant parameters 8. Thus external resistance could not be added to the rotor circuit.
One set is deeper closer to the shaft and the other set is commonly smaller and shallower closer to the. Doublecage rotor asynchronous induction motors for cement. To order a back issue with the full article, converting wound rotor motors to squirrel cage, call 3123219440 or visit our online webstore. Text books electrical machines ii notes em ii notes pdf em ii pdf.
Double cage induction motor introduction diy electrical. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. It is to make use of the fact that while high rotor figure 7. It is possible to produce a variable rotor resistance by the use of deep rotor bars or double cage rotors. Pdf analytical calculation of equivalent circuit parameters. 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. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. In double cage induction motor, the rotor consists of two cages or two layers of bars short circuited by end rings. Control of motorcharacteristics by squirrelcage rotordesign. Request pdf study of double cage induction motors with different rotor bar.
A double cage rotor has essentially two parallel rotor bar circuits built into the rotor. Vibration signature analysis for rotor broken bar diagnosis. The changes are made keeping the original flavor of the book intact, that is, indepth coverage of fundamental concepts. Electric motors and drives fundamentals, types and applications third edition austin hughes. Control of motorcharacteristics by squirrel cage rotordesign. 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. Generally in induction motor related operations, squirrel cage induction motors are widely used. The double cage rotor has two cages in which rotor winding is accommodated.
Study of double cage induction motors with different rotor bar. Deepbar or doublecage rotors of the induction motor have a high effective resistance at starting and a low effective resistance under normal running conditions. 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. Designing squirrel cage rotor slots with high conductivity. At high slips starting conditions, the reactances are large compared to the resistances in the rotor bars, so all the current is forced to flow in the lowreactance part of the bar near the stator. Double cage rotor of an induction motor circuit globe. 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. 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. 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. Double cage motor at starting s 1, f 2 f 1, the current mostly flows in the outer cage.
When the rotor is stationary or turnin g slowly the frequency of rotor currents is relatively high, the currents crowd to the top of the rotor bar and the resistive part of impedance is relatively high. The double cage behaves like a deep bar cage electric. Approximate equivalent circuits electric equipment. Broken rotor bar fault detection in inverterfed squirrel cage induction motors using stator current analysis and fuzzy logic mehmet akar1. 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.
Double cage induction motors are typically employed in applications that require high starting torque for frequent, loaded starts. More emphasis should be put on the acquisition of an inrushstartup test as a baseline. The figure of the double cage induction motor is shown below. The model of doublecage induction motor for the analysis.
Torquespeed curves influence of rotor parameters 211 cage rotor 211 double cage rotors 2 deep bar rotors 214 starting and runup of slipring motors 215 influence of supply voltage on torquespeed curve 217 generating and braking 218 generating region overhauling loads 219 plug reversal and plug braking 220 injection braking 221. We use cookies to offer you a better experience, personalize content, tailor advertising, provide social media features, and better understand the use of our services. Rotor bar width to depth geometry now depends on what torquespeed. The induction motor rotor is a completely shortcircuited conductive cage. The model is based on approximate analysis of the airgap and slot electromagnetic fields which leads directly to lumped circuit equations. To order a back issue with the full article, converting woundrotor motors to squirrelcage, call 3123219440 or visit our online webstore. Dynamic modelling of induction motor squirrel cage for. Based on the influence of the skin effect over electrical rotor parameters can be constructed a mathematical mode.
The upper cage has smaller crosssectional areas than the lower cage. The approximate equivalent circuit of double cage rotor. Mar 25, 2017 in some applications, very high starting torquetstarttrated. An induction motor can therefore be made without electrical connections to the rotor.
Advantage of double cage rotor over single cage rotor induction motor enesi asizehi yahaya tola omokhafe eugene o. The oemethodis able to estimate all double cageparameters with the same accuracy. Double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. It is similar to the deepbar rotor, except that the difference between lowslip and highslip operation is even more exaggerated. Electric machines by dp kothari and ij nagrath now in its 5. Its torquespeed characteristic is also shown in figure 726. Now when the motor is started, the current flows through the high resistance bar first and hence high starting torque. Deepbar cage rotor figure below shows a cage rotor with deep and narrow bars. Deep bar motor at starting s1, f 2 f 1, the current density is much higher at the top of the bar resulting in higher effective resistance. Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. May 02, 2016 before answering the question we have to know about types of rotors in induction motors. Deep bar visavis double cage rotor design for large mv motors free download as pdf file. Poly phase induction motorcircle diagram,deep bar and double cage rotor. Thus both r be and x be vary with slip frequency as they do in a deep bar single cage figure 9.
Power systems modelling and fault analysis theory and practice nasser d. Advantage of double cage rotor over single cage rotor. What is a double cage rotor, part 2 in the january 5, 2010 tip we discussed what a double cage rotor is. A bar may be assumed to be made up of number of narrow layers as shown in fig. The figure at left shows the cross sectional diagram of a double squirrel cage rotor.
An induction motor model with deepbar effect and leakage. Jre school of engineering preuniversity test may15. A possible alternative is either a high resistance bar or doublecage rotor design. The upper cage is called start cage, since the current at start flows mainly through this cage. An induction motor with two cage rotor is used for high starting torque. 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. Classes a and b have similar torquespeed characteristics. The sliptorque curve for deepbar rotor is shown below along with the deepbar stator. Pdf the paper aims to investigate the use of the finite element method for electrical and mechanical faults detection in threephase squirrel. Analytical calculation of equivalent circuit parameters accounting for deep bar effect in multiple cage squirrel cage rotor conference paper pdf available september 2014 with 119 reads. Dynamic modelling of induction motor squirrel cage for di. 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. Three double rotor bar induction motors have been simulated and their. A crosssectional view of a doublecage rotor is shown in figure 725c.
The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. A double cage rotor is another type of rotor whose effective resistance varies as shown in fig. Tag results found for electrical machines in files. Bars of high resistance and low reactance are placed in the outer cage, and bars of low resistance and high reactance are placed in the inner cage.
In deep bar induction motor, the rotor consists of deep bars, short circuited by two end rings one on each side. 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. Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque. In general, the farther away a rotor bar is from the stator, the. What are the merits and demerits of singlecage and double. The figure below shows a deep bar cage rotor with deep and narrow bars. Both methods are applied to single and double cagesimulation models. Such rotors are called double cage rotors or deep bar rotors. 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 twophase dynamic induction motor model is derived which includes the effects of rotor bar eddy currents and leakage inductance saturation. 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. Doublecage induction motors behavior under flicker conditions.
A squirrelcage motor with this type of rotor construction is called. As the name indicate the double cage induction motor has two winding in rotor. Performance analysis of three phase squirrel cage induction. Application note low inrush current motors help to reduce. Electrical machines 2 pdf notes em 2 pdf notes smartzworld. A bar may be assumed to be made up of a number of narrow layers connected in parallel. Deep bar or double cage rotors make use of skin effect. Figure 727a shows a current flowing through the upper part of a deep rotor bar. The basic concept is illustrated with a deep bar rotor in figure 727. Deep bar and multiple cage effects are useful in design of such machines. The skin effect is mostly relevant in the case of deep rotor bars and a doublecage structure. Broken rotor bar fault detection in inverterfed squirrel. 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. 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.
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