Class b has large and deep rotor bars, that is, the skin effect cannot be neglected during startup. The construction of stator for any induction motor is almost the same. Know about the construction of double squirrel cage motor with a graphical comparison with single cage. The motor rotor shape is a cylinder mounted on a shaft. 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. As the name indicate the double cage induction motor has two winding in. Know about the different winding slots, lamination of the stator and its construction. A double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. Generally in induction motor related operations, squirrel cage induction motors are widely used. A generalized two axes model of a squirrelcage induction motor for rotor. Torque speed characteristics of induction motor slip power. Remains same during starting and normal operating speed d. Double cage induction motor electrical engineers guide.
The effective resistance is small and running performance is improved. Advantage of double cage rotor over single cage rotor. Pdf emergency motor switchon happens occasionally while operating a doublesquirrel cage motor at full supply voltage with the rotor blocked e. The resistance of the upper cage winding is more than the inner c. The outer bars consists of rotor bars having low reactance and high resistance. Study of double cage induction motors with different rotor bar materials. Jun 12, 2016 the slotting arrangement for double cage induction motor is as shown in above figure. 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. Also appreciate the rugged construction of squirrel cage rotor and know.
Firstly, i am going to tell you about the structure of squirrel cage induction motor. This rotor is made up from parallel aluminum or copper bars. 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. Double cage rotor induction motor twinslotcage rotor. Pdf analytical modeling of double cage rotor induction motors in. Construction an induction motor with two cage rotor is used for high starting torque. But the rotor construction differs with respect to the type which is specified above. 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 stator of a double cage rotor of an induction motor is same as that of a normal induction motor. Double cage and deep bar squirrel cage rotor induction motor. Modeling and control of squirrel cage induction generator. The stator is the outer most component in the motor which can be seen. Double cage rotors an induction motor with two rotor windings or cages is used for obtaining high starting torque at low current.
Three phase squire cage induction motor, fully enclosed. The most popular squirrel cage induction motor is of a 4pole design. We saw the construction of the squirrel cage induction motor. On the other hand, the inner cage consists of rotor bars having high reactance and low resistance. Need for deepbar and double cage rotor deepbar rotors torqueslip relationship double cage rotors equivalent circuit diagram applications conclusion 3. There is a difference between single phase and three phase equivalent circuits. The name is derived from the similarity between this ringsandbars winding and a squirrel cage. The stator of a double cage induction motor is similar to that of ordinary induction motor. The squirrelcage winding in this design consists of. The output parameters of the single and the double cage rotor induction motor are shown in table 2 table 2. A squirrelcage rotor is the rotating part of the common squirrelcage induction motor. Classes a and b have similar torquespeed characteristics. Dec 27, 2015 an induction motor with two cage rotor is used for high starting torque.
The design and its verification of the double rotor double. Control of motorcharacteristics by squirrelcage rotordesign the reactance x2 in an induction motor equivalent circuit represents the referred form of the rotors leakage reactance. Double cage induction motor is used for cage rotor to increase rotor resistance so higher starting torque can achieve by this method. Former is cheaper and broadly used as it requires less maintenance than later one. Doubleslot rotors as well as doublecage rotors form the category of twinslotcage rotors. The rotor will constantly be turning to align its magnetic field with that of the stator field. Diagram of the double squirrel cage rotor with separate end rings on. Squirrel cage induction motor the engineering projects. Construction the three phase doublecage rotor asynchronous motor is. Dec 26, 2015 in this small post we will discuss about the double cage induction motor in brief.
Index terms induction motor, parameter estimation, standstill frequency response test. Equivalent circuit of a single phase induction motor. In pdmas january 5 tip, the company discussed what a doublecage rotor is. Doublecage rotors an induction motor with two rotor windings or cages is used for obtaining high starting torque at low current. How are squirrel cage induction motors constructed. May 12, 2017 the stator of a double cage rotor induction motor is the same as that ordinary induction motor. Double cage induction motor introduction diy electrical. 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. Low at starting and high at normal operating speed c. For a fullload operating slip of 3 per cent, the speed will then be 1 s60 fp, or 1455 rpm. Control of motorcharacteristics by squirrelcage rotordesign.
As the name indicate the double cage induction motor has two winding in rotor. The heat issues surrounding double squirrel cage motors operating in such conditions are represented only in a small number of publications 4. 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. 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.
Squirrel cage induction motor and wound rotor induction motor. 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. 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. Construction the three phase double cage rotor asynchronous motor is adequate for direct starting. This simplest form of ac induction motor or asynchronous motor is the basic, universal workhorse of industry. 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. In operation, the nonrotating stator winding is connected to. 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 3 phase induction motor has two types based on the rotor construction, named as. Double squirrel cage induction motor your electrical guide. 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. Need for deepbar and doublecage rotor deepbar rotors torqueslip relationship.
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. Output parameters of single cage and double cage rotor parameters single cage rotor double cage rotor starting torque, t st nm 4. The model of double cage induction motor for the analysis of thermal fields in transient operations. It consists of a cylinder of steel laminations, with aluminum or copper conductors embedded in its surface. Stator fundamental field induces rotor cage loops with rotor frequency. 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. Know about the most popular and almost unbreakable construction of squirrel cage 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. The figure below shows a deep bar cage rotor with deep and narrow bars. 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. This arrangement is used for obtaining high starting torque at a low value of starting current. Threephase squirrel cage induction motors are widely used as industrial drives because they are selfstarting, reliable and economical. 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. 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.
High during starting and low at normal operating speed b. What are the merits and demerits of singlecage and double. 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. An induction motor can therefore be made without electrical connections to the rotor. A double cage rotor has low starting current and high starting torque. The upper cage is having higher resistance than that of the lower cage. The squirrelcage winding in this design consists of two layers of bars shortcircuited by end rings. The double cage rotor has two cages in which rotor winding is accommodated.
The stator of a double cage rotor induction motor is the same as that ordinary induction motor. Pdf the model of double cage induction motor for the. A double squirrel cage induction motor consists of a rotor which has two independent cages one above the other in the same slot. Its synchronous speed with a 50 hz supply is therefore 60 fp, or 1500 rpm. More emphasis should be put on the acquisition of an in. Double cage rotor induction motor twinslot cage rotor double slot rotors as well as double cage rotors form the category of twinslot cage rotors. The model of doublecage induction motor for the analysis of thermal fields in transient operations. Recall that leakage reactance is the reactance due to the rotor flux lines that do not also couple with the stator windings. In this small post we will discuss about the double cage induction motor in brief. Therefore, it is more suitable for direct on line starting. Equivalent circuit for an induction motor electrical4u. Pdf analytical modeling of double cage rotor induction.
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. Pdf the model of doublecage induction motor for the analysis of. A generalized two axes model of a squirrelcage induction. 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. Construction of squirrel cage induction motor explained. Pdf the model of doublecage induction motor for the.
Torque speed characteristics of induction motor slip. Analytical modeling of double cage rotor induction motors in healthy and broken bars conditions. Cage induction machines institut fur elektrische energiewandlung. 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. 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. For the caged rotor of the induction motor, the doublecage model is better than the singlecage model.
In a slip ring induction motor, the rotor resistance is a. For single squirrelcage machines, provides a set of predetermined electrical and mechanical parameters for. The model of doublecage induction motor for the analysis. Starting torque is directly proportional to the 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. Double cage and deep bar squirrel cage rotor induction.
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. Squirrel cage wound rotor with slip rings the rotating magnetic field the basic idea of an electric motor is to generate two magnetic fields. After the successful tests beremend cement mills co. The model of doublecage induction motor for the analysis of. The rotor slot and rotor conductor has modified shape or modified peculiar shape can be draw or can be develop. 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. The heat issues surrounding doublesquirrelcage motors operating in such conditions are represented only in a small number of publications 4. To achieve this goal several simulations were performed using small signal model of a doublecage induction motor. Comparison between single cage and double cage motors. More emphasis should be put on the acquisition of an inrushstartup test as a baseline. The main difference between slip ring and squirrel cage induction motor is the rotor construction. Current versus speed characteristics, double cage rotor, induction. An induction motors rotor can be either wound type or squirrel cage type. Model the dynamics of threephase asynchronous machine.
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. 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. A combined use of current and vibration analysis was developed. The slotting arrangement for double cage induction motor is as shown in above figure. The rotor will constantly be turning to align its magnetic field. 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.
The deep and narrow rotor bars have the torquespeed characteristics similar to those of a doublecage rotor. 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. What is a squirrel cage motor and how does it work. The stator of a double cage rotor of an induction motor is same as that of a normal induction. Double cage rotor of an induction motor 6nq8vq6w61nw.
The upper slot conductors from the outer cage and the lower slot conductors form the inner cage. Doublecage induction motors behavior under flicker conditions. A double squirrel cage rotor is shown in the figure. Sep 18, 2019 the deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. Double cage rotors free download as powerpoint presentation. Vibration signature analysis for rotor broken bar diagnosis. An double cage induction motor is that type of motor in which a double cage or two rotor windings or cages are used. 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. An induction motor with two cage rotor is used for high starting torque. Oct 09, 2016 a 3 phase induction motor has two types based on the rotor construction, named as. Parameters estimation of squirrelcage induction motors. 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. The deep bar and double cage rotor are used to increase starting torque of squirrel cage induction motor. Then, the starting torque with increase but at the same time their will be more copper loss and %n of motor will decreases.
1341 992 636 1274 1149 1392 1503 886 431 571 504 364 1131 1265 1021 449 90 259 109 15 570 580 1147 164 701 1368 671 996 1495 759 994 1426 1356 602 713 1466