The stator of a double cage induction motor is similar to that of ordinary induction motor. Low at starting and high at normal operating speed c. Pdf emergency motor switchon happens occasionally while operating a doublesquirrel cage motor at full supply voltage with the rotor blocked e. The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. In this small post we will discuss about the double cage induction motor in brief. The stator of a double cage rotor of an induction motor is same as that of a normal induction. This arrangement is used for obtaining high starting torque at a low value of starting current. Double cage rotor of an induction motor 6nq8vq6w61nw. For single squirrelcage machines, provides a set of predetermined electrical and mechanical parameters for. The design and its verification of the double rotor double. The most used generator is the double feed induction generator dfig, and we suggest to change it by squirrel cage induction generator scig, owing to the robustness of scig, and since it has low cost with an almost null maintenance.
The stator is the outer most component in the motor which can be seen. Double cage rotor induction motor twinslotcage rotor. We saw the construction of the squirrel cage induction motor. How are squirrel cage induction motors constructed. Oct 04, 2017 as the motor speeds up, the rotor frequency decreases and the current distributes in both the cages of the double cage rotor or in the complete bar in the deep bar rotor. The deep and narrow rotor bars have the torquespeed characteristics similar to those of a doublecage rotor. A generalized two axes model of a squirrelcage induction. The rotor slot and rotor conductor has modified shape or modified peculiar shape can be draw or can be develop. In operation, the nonrotating stator winding is connected to. Classes a and b have similar torquespeed characteristics. Control of motorcharacteristics by squirrelcage rotordesign. Model the dynamics of threephase asynchronous machine. The double cage rotor has two cages in which rotor winding is accommodated.
Three phase squire cage induction motor, fully enclosed. Construction the three phase doublecage rotor asynchronous motor is. Double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. Vibration signature analysis for rotor broken bar diagnosis. An induction motor can therefore be made without electrical connections to the rotor. Since effective rotor resistance of double cage motor is higher, there is larger rotor heating at the time of starting as compared to that of single cage rotor.
A double squirrel cage induction motor consists of a rotor which has two independent cages one above the other in the same slot. In pdmas january 5 tip, the company discussed what a doublecage rotor is. After the successful tests beremend cement mills co. Doubleslot rotors as well as doublecage rotors form the category of twinslotcage rotors. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. An induction motor with two cage rotor is used for high starting torque. Cage induction machines institut fur elektrische energiewandlung.
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. Torque speed characteristics of induction motor slip power. What is a squirrel cage motor and how does it work. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry.
It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. On the other hand, the inner cage consists of rotor bars having high reactance and low resistance. The single phase induction motor circuit is given by double revolving field theory which states that. Need for deepbar and double cage rotor deepbar rotors torqueslip relationship double cage rotors equivalent circuit diagram applications conclusion 3. This rotor does not spin at the exact frequency of the ac current and is why squirrel cage motors as well as other induction motors are considered asynchronous. A generalized two axes model of a squirrelcage induction motor for rotor. Equivalent circuit for an induction motor electrical4u. The rotor will constantly be turning to align its magnetic field. The name is derived from the similarity between this ringsandbars winding and a squirrel cage. Index terms induction motor, parameter estimation, standstill frequency response test.
Construction the three phase double cage rotor asynchronous motor is adequate for direct starting. The resistance of the upper cage winding is more than the inner c. An double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. Pdf analytical modeling of double cage rotor induction motors in. The model of doublecage induction motor for the analysis. The upper slot conductors from the outer cage and the lower slot conductors form the inner cage. 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 consists of two cages or two layers of bars shortcircuited by end rings since the upper cage is having smaller crosssectional area than the lower cage. But the rotor construction differs with respect to the type which is specified above. As the name indicate the double cage induction motor has two winding in rotor. Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. Emergency motor switchon happens occasionally while operating a double squirrelcage motor at full supply voltage with the rotor. 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.
Firstly, i am going to tell you about the structure of squirrel cage induction motor. The motor rotor shape is a cylinder mounted on a shaft. The heat issues surrounding doublesquirrelcage motors operating in such conditions are represented only in a small number of publications 4. The outer bars consists of rotor bars having low reactance and high resistance. Double cage induction motor electrical engineers guide. May 12, 2017 the stator of a double cage rotor induction motor is the same as that ordinary induction motor. Hence the inductive reactance x l in the inner side bars or deep bars gets decreased and the current faces less inductive reactance and less resistance as a whole. There is always some loss, or slip, between the ac frequency and the rotational frequency of the shaft, and this is a consequence of why the rotor rotates in the first place. Know about the different winding slots, lamination of the stator and its construction.
The double cage motor is so develop that it overcomes the above difficulties and given good starting torque with good efficiency for that purpose. The squirrelcage winding in this design consists of. As the motor speeds up, the rotor frequency decreases and the current distributes in both the cages of the double cage rotor or in the complete bar in the deep bar rotor. More emphasis should be put on the acquisition of an inrushstartup test as a baseline. Double squirrel cage motor 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. 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. High during starting and low at normal operating speed b. Double cage rotors free download as powerpoint presentation. Pdf the model of doublecage induction motor for the analysis of. Squirrel cage induction motor and wound rotor induction motor.
The figure below shows a deep bar cage rotor with deep and narrow bars. The stator of a double cage rotor of an induction motor is same as that of a normal induction motor. Internally it contains longitudinal conductive bars usually made of aluminium or copper set into grooves and connected at both ends by shorting rings forming a cage like shape. The two rotors which are recommended to be double cage type for development of high starting torque can run with equal or unequal speed independently, depending on their individual loading. Double cage rotors an induction motor with two rotor windings or cages is used for obtaining high starting torque at low current.
Squirrel cage induction motor the engineering projects. Modeling and control of squirrel cage induction generator. The model of doublecage induction motor for the analysis of thermal fields in transient operations. Analytical modeling of double cage rotor induction motors in healthy and broken bars conditions conference paper pdf available november 2014 with 810 reads how we measure reads. The rotor consists of two cages or two layers of bars shortcircuited by end rings since the upper cage is having smaller crosssectional area than. Also appreciate the rugged construction of squirrel cage rotor and know. The stator of a double cage rotor induction motor is the same as that ordinary induction motor. Construction of squirrel cage induction motor explained. Output parameters of single cage and double cage rotor parameters single cage rotor double cage rotor starting torque, t st nm 4. Need for deepbar and doublecage rotor deepbar rotors torqueslip relationship. Doublecage rotors an induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. Parameters estimation of squirrelcage induction motors.
As the name indicates, the double cage induction motors have two cages in the rotor and they have the advantages of. The concept of a double rotor motor presented earlier and its equivalent circuit has been developed, showing a nonlinear parameter content. The squirrelcage winding in this design consists of two layers of bars shortcircuited by end rings. 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. Comparison between single cage and double cage motors. Double cage and deep bar squirrel cage rotor induction motor. Recall that leakage reactance is the reactance due to the rotor flux lines that do not also couple with the stator windings. More emphasis should be put on the acquisition of an in. The heat issues surrounding double squirrel cage motors operating in such conditions are represented only in a small number of publications 4. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. A 3 phase induction motor has two types based on the rotor construction, named as.
Remains same during starting and normal operating speed d. Generally in induction motor related operations, squirrel cage induction motors are widely used. Analytical modeling of double cage rotor induction motors in healthy and broken bars conditions. Therefore, it is more suitable for direct on line starting. Pdf analytical modeling of double cage rotor induction. An induction motors rotor can be either wound type or squirrel cage type. The model of doublecage induction motor for the analysis of. A double cage rotor has low starting current and high starting torque. Control of motorcharacteristics by squirrelcage rotordesign the reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance. Starting torque is directly proportional to the rotor resistance. 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 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.
The slotting arrangement for double cage induction motor is as shown in above figure. For the caged rotor of the induction motor, the doublecage model is better than the singlecage model. The upper cage is having higher resistance than that of the lower cage. Current versus speed characteristics, double cage rotor, induction. There is a difference between single phase and three phase equivalent circuits. Deep bar rotor see in first figure during starting conductor in upper slot are active due to majority of current flowing through these conductor because conductor in lower slot have large leakage flux hence large lea. The output parameters of the single and the double cage rotor induction motor are shown in table 2 table 2.
As the name indicate the double cage induction motor has two winding in. Double cage and deep bar squirrel cage rotor induction. The rotor will constantly be turning to align its magnetic field with that of the stator field. 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. Study of double cage induction motors with different rotor bar materials. In a slip ring induction motor, the rotor resistance is a. Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. Former is cheaper and broadly used as it requires less maintenance than later one.
Torque speed characteristics of induction motor slip. This paper presents a double cage motor model with a cast structure rotor and a soldered cage to analyse the thermal field of the rotor in selected, severe operating conditions. A double squirrel cage rotor is shown in the figure. To achieve this goal several simulations were performed using small signal model of a doublecage induction motor. The main difference between slip ring and squirrel cage induction motor is the rotor construction. The effective resistance is small and running performance is improved. Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. Know about the construction of double squirrel cage motor with a graphical comparison with single cage.
The model of double cage induction motor for the analysis of thermal fields in transient operations. 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. Construction an induction motor with two cage rotor is used for high starting torque. 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.
Double cage rotor a rotor design, which though more expensive gives still better starting, and running performances than the deepbar design, is the doublecage rotor. Double squirrel cage induction motor your electrical guide. A combined use of current and vibration analysis was developed. Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. 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.
Doublecage induction motors behavior under flicker conditions. Stator fundamental field induces rotor cage loops with rotor frequency. Dec 26, 2015 in this small post we will discuss about the double cage induction motor in brief. A double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used.
Diagram of the double squirrel cage rotor with separate end rings on. Pdf the model of doublecage induction motor for the. This paper presents a doublecage motor model with a cast structure rotor and a soldered cage to analyse the thermal field of the rotor in selected, severe operating conditions. Know about the most popular and almost unbreakable construction of squirrel cage induction motor. Jun 12, 2016 the slotting arrangement for double cage induction motor is as shown in above figure. Pdf the model of double cage induction motor for the. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm. Advantage of double cage rotor over single cage rotor. Equivalent circuit of a single phase induction motor. Oct 09, 2016 a 3 phase induction motor has two types based on the rotor construction, named as.
On the other hand, the rotor current mainly flows in the symmetric inner cage under steady state operating condition, and fault signature is insensitive to outer cage damage. Then, the starting torque with increase but at the same time their will be more copper loss and %n of motor will decreases. Double cage induction motor introduction diy electrical. The most popular squirrel cage induction motor is of a 4pole design. The construction of stator for any induction motor is almost the same.
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