What is the double revolving field theory for a single. Double revolving field theory of single phase induction. Both the theories are similar and explain the reason for the production of torque when the rotor is rotating. The rotor is cylindrical and has slots all over its periphery. Mathematically, the pulsating field could be divided. Also, check out cross field theory of single phase induction motor. Single phase induction motor double revolving field theory the two equivalent circuits are connected in series. Single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of parameters methods of starting, split phase starting, repulsion starting, shaded pole starting, performance characteristics. Performance characteristics and double revolving theory of single phase induction motor yahaya asizehi enesi 48 figure 2 shows the powerslip characteristic of a single phase induction motor. Single phase induction motor double field revoling theory making single phase induction motor selfstarting equivalent circuit of. Consider two magnetic fields represented by quantities oa and ob of equal magnitude revolving in opposite directions as shown in fig the resultant of the two fields of equal magnitude rotating in opposite directions is alternating.
Single phase induction motor electric motor electrical. Equivalent circuit for an induction motor electrical4u. One is foreward rotating field and the other one is backward rotating filed which produces foreward and backward torques. The performance of the single phase induction motor is analysed by the two theories. A single phase ac current supplies the main winding that produces a pulsating magnetic field. Double revolving field theory application of single phase. Double revolving field theory a single phase ac current supplies the main winding that produces a pulsating magnetic field.
The current, power and torque can be calculated from the combined equivalent circuit using the ohm law. Zb 19 the current through backward rotor referred to stator is given as. According to double revolving field theory, consider the two components of the stator flux, each having magnitude half of maximum magnitude of stator flux i. Electrical mcs and power utilization pdf book agrimoon. Double rotating field theory of the singlephase induction motor. The method consists of determining the values of both the fields clockwise and anticlockwise at any given slip. Feb 16, 2020 it is interesting to know how a singlephase induction motor can able to rotate when an initial rotation or starting torque is given to it. Double revolving field theory of single phase induction motor consider two magnetic fields represented by quantities oa and ob of equal. The various possibilities in the design modification, speed control, efficiency, power factor improvement of induction motor and double winding induction motors are discussed below. The induction motor responds to each of the magnetic fields separately.
Aug 04, 2020 single phase induction motors and special machinesconstructional details of single phase induction motor double revolving field theory and operation equivalent circuit no load and blocked rotor test performance analysis starting methods of single phase induction motors special machine shaded pole induction motor. Double revolving field theory of single phase induction motor. At standstill, the revolving magnetic field passes the rotor bars at a high rate, inducing linefrequency current into the rotor bars. Double rotating field theory of the single phase induction motor. To overcome this drawback and make the motor selfstarting, it is temporarily converted into a two phase motor during starting period. The slots are not made parallel to each other but are a little bit skewed as the skewing prevents magnetic locking of stator and rotor teeth and makes the. There are two basic theories which explain why a torque is produced in the rotor once it is turning. Unlike in 3phase induction motor, where a rotating magnetic field is setup in the stator core, a plain singlephase induction motor, shown in fig 8. This theory makes use of the idea that an alternating uniaxial quantity can be represented by two oppositely rotating vectors of half magnitude. The single phase induction motor operation can be described by two methods. Single phase series motor, theory of operation performance and application, shcrage motor.
Consistent with this theory, any alternating amount may be resolved into rotating additives which rotate in contrary instructions and every. Working principle of a single phase induction motor circuit globe. They are equal in magnitude but opposite in directions. Singlephase induction motor construction, working, types. Performance characteristics and double revolving theory of. Performance characteristics and double revolving theory of single. The principle of operation of a singlephase induction motor can be explained from the cross field theory. Consider two magnetic fields represented by quantities oa and ob of equal magnitude revolving in opposite directions as shown in fig. Double field revolving theory ac current flows through the stator two fields are generated 1f forward rotating field 2bbackward rotating field pulsating field due to various magnitudes of field at diff time 2 3.
May 20, 2014 the single phase induction motor operation can be described by two methods. Two theories have been suggested to find the performance of a single phase induction motor. The analysis of the single phase motor can be made on the basis of two theories. Double revolving field theory let us see why single phase induction motors are not self starting with the help of a theory called double revolving field theory. The difference between the forward and the backward torque is the net torque acting on the rotor. Unitv, single phase induction motor by vikashtiwari page 1 1.
Why 1 phase induction motor is not self starting rotor squirrel cage type rotor alternating flux not required to produce rmf. It describes about the rotating magnetic fields in electrical machines like induction motor. An ac motor starts through an exterior source however it needs an extra space of about 30% than a three phase motor. Equivalent circuit of single phase induction motor.
The resultant of the two fields of equal magnitude rotating in opposite directions is alternating. Double revolving field theory and principle of operation. Single phase induction motor, theory of operation double revolving field theory, equivalent circuit, determination of parameters methods of starting, split phase. Double revolving theory double revolving field theory of single phase induction motorthis theory is used to analyse the performance of single phase inducti. The equivalent circuit of a single phase induction motor can be obtained by two methods named as the double revolving field theory and cross field theory.
The most used types of singlephase motors in the world eep. A rotating magnetic field can be produced by a poly phase two or more phases current or by a single phase current provided that, in the latter case, two field windings are supplied and are so designed that the two resulting magnetic fields. Apr 25, 2018 but once an induction motor is started by any means in any direction, it continues to run in that direction. Single phase and special purpose motors philadelphia university.
Doublerevolving field theory of single phase induction motors. A rotating magnetic field is the resultant magnetic field produced by a system of coils symmetrically placed and supplied with polyphase currents. The input power gradually increases with corresponding increase in the slip until it gets to its maximum operating characteristic. Single phase motor working, types, double field revolving. Due to this, the single phase induction motor has no starting torque. Single phase induction motor constructional features double revolving field theory equivalent circuit split phase motors capacitor start capacitor run motors. The shape and depth of the rotor bars can be used to vary the speedtorque characteristics of the induction motor.
Feb 16, 2020 when initial rotation is given to the rotor in any direction, the overall torque increases in that direction and the motor starts giving the performance similar to the 3 phase induction motor. Performance characteristics and double revolving theory of single phase induction motor yahaya asizehi enesi 46 torque due forward rotating field of the rotor. According to this theory, any alternating quantity can be resolved into two rotating components. Single phase motor main winding generates t wo rotating fields mathematically, the pu lsating field could be divided into two fields, which are rotating in opposite directions. Types of single phase induction motors and double revolving. This strange behavior of single phase induction motor can be explained on the basis of double field revolving theory. Now, from the above explanation, we can conclude that the single phase induction motor is not selfstarting. According to this theory, any alternating quantity can be resolved into two rotating components which rotate in opposite directions and each having magnitude as half of the maximum magnitude of the alternating quantity. Motor double field revolving theory ac current flows through the stator two fields are generated 1. Theory and analysis of three phase induction motor using. Considering the case when the rotor is stationary and only the main winding is excited. Mathematically, the pulsating field could be divided into two fields, which are rotating in opposite directions. How can we explain this amazing feature of single phase induction motor.
The magnetic field of the single phase motor does not rotate and it creates pulses in the same and opposite direction. Figure 44 shows the equivalent circuit of a single phase motor in running condition. The equivalent circuit diagram of the single phase motor with only its main winding energized the is shown below. The double revolving field theory can be effectively used to obtain the equivalent circuit of a single phase induction motor. Pdf lecture 1 single phase induction motor sri vidhya. Working principle of a single phase induction motor javatpoint. Working principle of a single phase induction motor. The double revolving field theory of a single phase induction motor states that a pulsating magnetic field is resolved into two rotating magnetic fields. Unlike in 3phase induction motor, where a rotating magnetic field is setup in the stator core, a plain single phase induction motor, shown in fig 8. Single phase field consider an induction motor with a stator winding connected to a single phase supply. The motor behaves as a single phase transformer with its secondary short circuited. Working principle of a single phase induction motor circuit.
This describes the construction, synchronous speed, slip, torque speed characteristic, double revolving field theory. Revolving field theory of single phase induction motors. This video is about the electric and magnetic fields. Two fields are determined and the torque produced by each field is obtained. Double revolving field theory is based on an alternating sinusoidal flux can be expressed by two revolving fluxes and each flux equal to one. Double revolving theory double revolving field theory of. Home single phase motor working, types, double field revolving theory double field revolving theory. To make this motor selfstarting motor, we need stator flux rotating in nature instead of alternating nature. For this purpose, the stator of a single phase motor is provided with an extra winding. In this singlephase induction motor slip rings and commutators are not used, so their construction becomes very simple and easy. Double revolving theory is perhaps the easier of the two explanations to understand learn the double revolving theory only. To explain this, we need the concept of revolving field theory. T his theory is known as double revolving theory or double field revolving theory.
In a single phase induction motor, according to double revolving field theory, there will be two fields with same magnitude but rotating in opposite directions. You may like to read, why 3 phase induction motors are selfstarting but 3 phase synchronous motors not. Consider standstill conditions with the stator winding connected to a single phase ac supply. Firstly the equivalent circuit is developed on the basis of double revolving field theory when only its main winding is energized.
Synchronous machine connected to bus and operating as motor. A single phase induction motor exhibits a pulsatingintime air gap field and a pulsating torque. Based on double revolving field theory the equivalent circuit of the single phase induction motor can be drawn. Double revolving field theory in singlephase induction motors.
What is the double revolving field theory for a singlephase. Making single phase induction motor selfstarting as discussed above, a single phase induction motor is not selfstarting. Single phase induction motor working, construction. Double revolving theory is perhaps the easier of the two explanations to understand learn the double revolving theory only principle operating 8. Induction motor theory is in this article we will discuss about double field revolving theory in induction motor. Single phase motor is nothing but a running a squirrel cage induction motor using a single phase power supply. This can understand with the help of cross field theory and double revolving field theory.
One is known as the double revolving field theory, and the other is cross field theory. Oct 25, 2020 the construction of the rotor of the single phase induction motor is similar to the squirrel cage three phase induction motor. Polyphase motor phase diagram, torque equation, starting and speed control methods. Equivalent circuit of a single phase induction motor. Single phase induction motor double revolving field theory the three phase induction motor starting torque inversely depends on the slip this implies that a small positive slip 0. Double revolving feild theory single phase induction motor. Double revolving field theroy electrical engineering.
In order to obtain a revolving air gap field and electromagnetic. Oct 16, 2020 double revolving field theory is based on the fact that an alternating sinusoidal flux can be expressed by two revolving fluxes and each flux equal to one half of the maximum value of alternating flux. The double revolving field theory is used to develop the equivalent circuit of single phase induction motor. A coil carrying ac produces a magnetic field as per the basic law of em, but not rotating field, it just. This can be considered to generate two counter rotating magnetic fields, as shown in figure 1a. Single phase induction motor double revolving field theory the pulsating filed is divided a forward and reverse rotating field motor is started in the direction of forward rotating field this generates small 5% positive slip reverse rotating field generates a larger 1. Sep 06, 2019 this motor starts automatically self but a 1 phase induction motor will not start automatically because it cannot expand starting torque. Dec 11, 2020 an induction motor also known as an asynchronous motor is a commonly used ac electric motor.
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