What is a double cage rotor, part 2 in the january 5, 2010 tip we discussed what a double cage rotor is. In this small post we will discuss about the double cage induction motor in brief. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol. These machines, because of their rotor bar design, exhibit a high rotor resistance to the flow of negative sequence currents and produce extreme heating during unbalanced conditions. 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. Deepbar model the mathematical approach in terms of modeling for a deepbar and doublecage rotor construction is similar. If an induction machine with closed or skewed rotor slots is studied, the model for saturation should be extended. The net reactance of deep bar rotor at standstill is higher than that in a normal bar design. Deep bar or double cage rotors are used in squirrel cage. In a slip ring induction motor, the rotor resistance is a. Classes a and b have similar torquespeed characteristics. Mar 25, 2017 in some applications, very high starting torquetstarttrated.
This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. Pdf skin effect modelling in induction motors rotor deep bars. The changes are made keeping the original flavor of the book intact, that is, indepth coverage of fundamental concepts. Double cage rotors free download as powerpoint presentation. Deep bar or double cage rotors are used in squirrel cage induction motor to obtain published on 27 oct 15. The deep bar rotor has a single cage, usually of copper, formed in slots which are deeper and narrower than in a conventional singlecage design. 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. As the name indicates, the double cage induction motors have two cages in the rotor and they have the advantages of both squirrelcage induction motors and wound rotor induction motors. Indirect vector control of multi cage induction motor citeseerx.
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. Double cage and deep bar squirrel cage rotor induction. A bar may be assumed to be made up of number of narrow layers as shown in fig. Double cage equivalent of deep bar rotor motor electric. The model is based on approximate analysis of the airgap. The model of doublecage induction motor for the analysis of. In pdmas january 5 tip, the company discussed what a doublecage rotor is. More emphasis should be put on the acquisition of an inrushstartup test as a baseline.
Both rotor types can be effectively modeled using two windings perphase in the rotor. The invention relates to a cage rotor for an asynchronous machine 1 comprising starting bars for improving the starting behavior. Three double rotor bar induction motors have been simulated and their. 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. 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 parameters are estimated either in the transient state or in the steady state by using a curve. Deepbar cage rotor figure below shows a cage rotor with deep and narrow bars. What are the merits and demerits of singlecage and double. Harley and yao duan georgia institute of technology november, 2009. 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 rotor consists of deep bars, short circuited by two end rings one on each side. 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. Construction is simpler and therefore cheaper than in a doublecage rotor, as shown on the right in fig.
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. The invention further relates to a method for producing such a cage rotor. The parameters are estimated either in the transient state or. Current versus speed characteristics, double cage rotor, induction motor. Based on the influence of the skin effect over electrical rotor parameters can be constructed a mathematical mode. A double cage rotor has essentially two parallel rotor bar circuits built into the rotor. Hence breakdown or pull ot torque in deep bar rotor is lower. An induction motor model with deepbar effect and leakage. This paper presents a doublecage induction motor model for analysis of thermal fields in transient operation. Apr 17, 2015 the sliptorque curve for deep bar rotor is shown below along with the deep bar stator. 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. The model of double cage induction motor for the analysis of thermal fields in transient operations. The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. These drawbacks are removed by a double squirrel cage motor, which has high starting torque without sacrificing efficiency.
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. Study of double cage induction motors with different rotor bar materials. Designing squirrel cage rotor slots with high conductivity. The double cage behaves like a deep bar cage electric equipment. Advantage of double cage rotor over single cage rotor. Mar 04, 2016 the squirrel cage induction motor is widely used rotor copper losses are high and hence less efficiency less rotor copper losses and hence high efficiency speed control by rotor resistance method is possible speed control by rotor resistance method is not possible slip ring induction motor are used where high starting torque is required i. Consequences of broken rotor bars rotor windings in squirrel cage induction motors are manufactured from aluminum alloy, copper, or copper alloy. An induction motors rotor can be either wound type or squirrelcage. 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. 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. 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. Massachusetts institute of technology cambridge, massachusetts, 029, usa. Introduction as stated in prior research l, 2, while starting up the deepbar and doublesquirrelcage. The rotor of the three phase induction motor are further classified as squirrel cage rotor, slip ring rotor or wound rotor or phase wound rotor.
More emphasis should be put on the acquisition of an inrushstart. Designing squirrel cage rotor slots with high conductivity james l. Deep bar cage rotor figure below shows a cage rotor with deep and narrow bars. Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. In some applications, very high starting torquetstarttrated. Construction is simpler and therefore cheaper than in a double cage rotor, as shown on the right in fig.
The double cage behaves like a deep bar cage electric. Double cage induction motor introduction diy electrical. It is seen that the top most layer element a is linked with minimum leakage flux and therefore its leakage inductance is minimum. 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.
Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque. Pdf electric machines by dp kothari and ij nagrath pdf download. The squirrel cage with deep rotor bars can be equivalent with a double cage, one of these cages having constant parameters 8. Generally in induction motor related operations, squirrel cage induction motors are widely used. The sliptorque curve for deep bar rotor is shown below along with the deep bar stator.
The rotor is connected to the mechanical load through the shaft. One set is deeper closer to the shaft and the other set is commonly smaller and shallower closer to the. A triplecage circuit of a deepbar induction motor is numerically identified in the time domain. Three phase squire cage induction motor, fully enclosed.
An induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. There is no constructional difference between stator of seep bar rotor motor and that of ordinary induction motor. A triple cage circuit of a deep bar induction motor is numerically identified in the time domain. One set is deeper closer to the shaft and the other set is commonly smaller and shallower closer to the stator. The sliptorque curve for deepbar rotor is shown below along with the deepbar stator. 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. 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. 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. The rotor of of an induction motor can be designed in two types. Dec 26, 2015 in this small post we will discuss about the double cage induction motor in brief. Performance analysis of three phase squirrel cage induction. Nov 01, 2004 broken bars cause torque and speed oscillations in the rotor, provoking premature wear of bearings and other driven components. The model of doublecage induction motor for the analysis of thermal fields in transient operations. Double cage and deep bar squirrel cage rotor induction motor.
Parameter estimation for a deepbar induction motor. As stated in prior research l, 2, while starting up the deepbar and doublesquirrelcage. This article presents a way to analyze the skin effect, in the deep bars of induction motors im. Im design above 100kw and constant v and f size your own im high voltage stator design. The skin effect is mostly relevant in the case of deep rotor bars and a doublecage structure. Gersh, finite element calculation of double cage rotor equivalent circuit parameters, ieee trans. On the other hand, the inner cage consists of rotor bars having high reactance and low resistance. This paper presents a doublecage induction motor model for ana lysis of thermal. Redistribution of current in deep bar cage rotors as a result of. Traditional design of cage rotor induction motors ronald g. This includes the starting and running values of the rotor single cage equivalent circuit.
Ac motors, heating, induction motors, squirrel cage motors, temperature rise 1. The model of doublecage induction motor for the analysis. 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 stator of a double cage rotor of an induction motor is same as that of a normal induction motor. A twophase dynamic induction motor model is derived which includes the effects of rotor bar eddy currents and leakage inductance saturation.
May 02, 2016 before answering the question we have to know about types of rotors in induction motors. Torqueslip characteristics covering motoring, generating and braking regions of operation, induction generator, noload and blocked rotor tests, circle diagram and therefrom performance evaluation of the motor, cogging and crawling, equivalent circuit and performance of doublecage and deepbar motors. Before answering the question we have to know about types of rotors in induction motors. The slotting arrangement for double cage induction motor is as shown in above figure. As the name indicate the double cage induction motor has two winding in rotor. At startup, the reactance of these bars is large compared to the resistance, resulting in. This arrangement is used for obtaining high starting torque at a low value of starting current. The double cage rotor has two cages in which rotor winding is accommodated. A doublecage rotor has essentially two parallel rotor bar circuits built into the rotor. Now consider that the bar consists of many number of layers. Nema class b design has large and deep rotor bars accommodated. The stator of a double cage induction motor is similar to that of ordinary induction motor.
Double cage induction motor electrical engineers guide. Pdf electric machines by dp kothari and ij nagrath pdf. Detecting broken rotor bars prevents catastrophic damage. Slip ring rotor for both of them the stator part connection is same. An induction motor can therefore be made without electrical connections to the rotor. Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. The electrical machines ii notes pdf em ii pdf notes em ii notes pdf file to download are listed below please check it.
Starting performance torque of induction machine has improved. The outer bars consists of rotor bars having low reactance and high resistance. 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 2009. The magnetic leakage flux lines are shown by dotted lines. Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. Electrical machines 2 pdf notes em 2 pdf notes smartzworld. Diagnosis and fault detection in electrical machines and. Vibration signature analysis for rotor broken bar diagnosis. Another phenomenon that is usually omitted within the smallsignal analysis is the skin effect of rotor bars. The induction machines design handbook 2nd edition ion. The starting cage features a large active resistance and low leakage reactance, whereas the operation cage oppositely shows low active resistance.
Electric machines by dp kothari and ij nagrath now in its 5. Pdf the model of doublecage induction motor for the. Parameter estimation for a deepbar induction motor request pdf. It is usually designed for fixedspeed operation, larger ratings having such features as deep rotor bars to limit direct on line dol starting currents. 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. The figure below shows a deep bar cage rotor with deep and narrow bars. Introduction as stated in prior research l, 2, while starting up the deep bar and double squirrel cage. Smallsignal model for saturated deepbar induction machines. Improvements in deep bar rotor induction motors us3290526a. This reduces the evidence of a faulty rotor bar and may.
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