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. This behavior of a single phase motor can be explained by double field revolving theory. Consider two magnetic fields represented by quantities oa and ob of equal magnitude revolving in opposite directions as shown in fig. Therefore, single phase induction motors are not self starting motor. Some single phase induction motors are also called squirrel cage motors because of the rotors similarity. Single phase induction motors questions and answers. Equivalent circuit of a single phase induction motor. Double revolving field theory crossfield theory double revolving field theory a singlephase ac current supplies the main winding that produces a pulsating magnetic field. Since single phase induction motor requires the generation of the rotating magnetic field similar to that of three phase motor, this is achieved by converting the. Double revolving field theroy electrical engineering. Double field revolving theory of single phase induction motor. Suppose the rotor is locked, if an ac voltage is applied to the stator, the resulting current i s produces an ac flux f s. The circuit diagram of this motor at the starting condition is illustrated below.
Equivalent circuit of single phase induction motor. Double revolving field theory of single phase induction. Double revolving feild theory single phase induction motor. Jan 02, 2017 operating principle the singlephase induction motor operation can be described by two methods. The net torque in the motor is equal to the sum of the torque. Revolving field theory of single phase induction motors. The theory used in the work was collected by studying literature on how electrical motors work, and by simplifying the explanations to suit the intended. In case of singlephase induction motors, the stator winding produces an alternating magnetic field having the maximum magnitude of. Mathematically, the pulsating field could be divided into two fields, which are rotating in opposite directions. The 3phase set of currents, each of equal magnitude and with a phase. Double revolving field theory in singlephase induction motors. Double revolving theory is perhaps the easier of the two explanations to understand learn the double revolving theory only. Why is a singlephase induction motor not selfstarting, but. According to doublerevolving field theor y, consider the two components of the stator flux, each having magnitude half of maximum magnitude of stator flux i.
Jul 12, 20 in case of single phase induction motors, the stator winding produces an alternating magnetic field having maximum magnitude of. Two fields are determined and the torque produced by each field is obtained. The construction of a single phase induction motor is very similar to that of a 3 phase induction motor. Cross field revolving theory is the theory which discuss the cause of single phase induction motor not to be self starting. Aug, 20 when only single power phase is available, single phase motors are the natural choice out of wide variety of electric motors.
Aug 10, 2016 construction of single phase induction motor. In a single phase motor we have only a single field winding excited with alternating current. Sep 06, 2019 based on the double field revolving theory equivalent circuit is developed. Figure 1 is a schematic diagram of the rotor and main winding of a twopole single phase induction motor. And gives more torqueamp than any other single phase motor. Firstly the equivalent circuit is developed on the basis of double revolving field theory when only its main winding is energized. A single alternating magnetic field having a field strength phi can be. Single phase im double field revolving theory youtube. Working principle of a single phase induction motor javatpoint. The basic idea of an electric motor is to generate two magnetic fields. 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. For reason of economy, most houses, offices and also rural areas are supplied with single phase a. In this singlephase induction motor slip rings and commutators are not used, so their construction becomes very simple and easy. Double revolving field theory application of single phase.
Single phase induction motor working, construction. They are equal in magnitude but opposite in directions. Most single phase induction machines are small and built in the fractional horsepower range. The double revolving field theory of a single phase induction motor states that a pulsating magnetic field is resolved into two rotating magnetic. To make a single phase induction motor selfstarting, we should somehow produce a revolving stator magnetic field. Working principle of a single phase induction motor. Based on double revolving field theory the equivalent circuit of the single phase induction motor can be drawn. Since losses are different at different loads and are not directly proportional to the output, efficiency will be different at different loads.
The construction of the stator of the singlephase induction motor is similar to that of three phase induction motor except there are two dissimilarities in the winding part of the single phase induction motor. Consider a single phase induction motor with standstill rotor as shown in the fig. Need for starter, dol, ydelta and autotransformer starting, rotor resistance starting, electronic starters, speed control voltage, frequency and rotor resistance variations. The single phase induction motor is the most frequently used motor for refrigerators, washing machines, clocks, drills, compressors, pumps, and so forth. 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. Single phase induction motor double revolving field theory each of the rotating fields induces a voltage in the rotor, which drives current and produces torque. Performance characteristics and double revolving theory of single phase induction motor yahaya asizehi enesi 42 theory that is applicable to variety of induction motor types.
Double revolving field theory of single phase induction motor double revolving field theory engineering list seven. Making single phase induction motor selfstarting as discussed above, a single phase induction motor is not selfstarting. The rotor is a rotating part of an induction motor. It is also the area of greatest component failure and maintenance requirements, in fact, the specific names for induction motors represent the means in which the revolving field is developed from a single phase power source. The torque speed curve for a single phase induction machine can be sketched as the sum of two torque speed curves one tying to drive the machine in the. The double revolving field theory of a single phase induction motor states that a pulsating magnetic field is resolved into two rotating magnetic fields. Double revolving theory is perhaps the easier of the two explanations to understand 7. May 22, 2016 according to double revolving discipline principle, bear in mind the 2 additives of the stator flux, every having significance half of maximum magnitude of stator flux i. Performance characteristics and double revolving theory of. Double revolving field theory a single phase ac voltage supplies the main winding that produces a magnetic field change with time around one access so that this field call as pulsating. According to the double field theory, the stator flux is divided into two components, which is equal to half of the magnitude.
Double revolving theory is perhaps the easier of the two explanations to understand so we will discuss the double revolving theory only. Equivalent circuit for an induction motor electrical4u. The main components of a single phase motor are the rotor and stator winding. This is a key principle in the operation of the alternatingcurrent motor rotating magnetic fields are often utilized for electromechanical applications such as induction motors and. Jun 05, 2011 the single phase induction motor resembles, three phase, squirrelcage motor except that, at full speed, only a single winding in the stator is excited. The single phase induction motor operation can be described by two methods. This theory explains why the motor is not selfstarting. The following section describes about the double revolving field theory and the prtnciple of operation of single phase induction motors. The basic idea behind the double field revolving theory is that any alternating. Single phase induction motor is very simple and robust in construction. Stator winding produced alternating fluxes and can be presented as a sum of two rotating fluxes. Double revolving field theory and principle of operation, types of single phase.
Single phase motor can be wound for any even number of poles i. The singlephase induction motor operation can be described by two methods. Single phase motors are classified according to the methods of starting used for them. Input can be expressed as the sum of the output and losses. Such a motor inherently docs not develop any starting torque and, therefore, will not start to rotate if the stator winding is connected to singlephase a. Single phase field consider an induction motor with a stator winding connected to a single phase supply. It describes about the rotating magnetic fields in electrical machines like induction motor. This video is about the electric and magnetic fields.
The double revolving field theory of singlephase induction motors the double revolving field theory of singlephase induction motors basically states that a stationary pulsating magnetic field can be resolved into two rotating magnetic fields, each of equal magnitude but rotating in opposite directions. There are a multitude of single phase motor combinations. The rotor in the single phase induction motor is of squirrel cage rotor type. The efficiency of any device is the ratio of its output and input. The flux alternates back and forth but, unlike the flux in three phase stator, no revolving field is produced.
The difference between the forward and the backward torque is the net torque acting on the rotor. Case of 3ph induction motor, stator winding is of 3ph and a 3ph ac supply. Ideally, the rotation changes direction at a constant angular rate. Aug 24, 2018 there is a difference between single phase and three phase equivalent circuits. The induction motor responds to each of the magnetic fields separately. Single phase series motor, theory of operation performance and application, shcrage motor.
Starting and control of three phase induction motor. This theory for single phase states that a stationary pulsating magnetic field can be resolved into two rmf, each of equal magnitude but rotating in the opposite direction. The double revolving field theory is used to develop the equivalent circuit of single phase induction motor. This strange behavior of single phase induction motor can be explained on the basis of double field revolving theory. Working principle of a single phase induction motor circuit. It operates based on the double field revolving theory.
Double field revolving theory the double field revolving theory states that, any alternating quantity here, alternating flux can be resolved into two components having magnitude half of the maximum magnitude of the alternating quantity, and both these. When supply is given to the stator, stator flux m is developed due to the current flow in the winding. Before going into the details of revolving field theory, first we should know why do we need to study this theory. Consider case 1, that rotor is at a standstill and single phase induction motors stator winding connected to single phase supply. Rotating magnetic field in a single phase ac motor. Applying double revolving field theory, it is possible to think of a single phase induction machine as the sum of two smaller induction machines, each trying to rotate in opposite directions. Performance characteristics and double revolving theory of single. Double field revolving theory the double field revolving theory of single phase induction motor is proposed to explain this problem of no torque developed at starting and yet torque once rotated.
Due to the double field revolving theory, the alternating stator flux is divided into two components namely, forward field and backward field respectively. A rotating magnetic field is a magnetic field that has moving polarities in which its opposite poles rotate about a central point or axis. Read more revolving field theory of single phase induction motors. There are two basic reasons for the use of singlephase motors rather than 3phase motors. Synchronous generator constructional details types of rotors emf equation synchronous reactance armature reaction voltage regulation e.
Jul 11, 2019 as its name indicates stator is a stationary part of induction motor. In motors that operate with both windings energized,the winding with more wire more turns is known as main winding and the other is called auxiliary winding. Imagine the single phase induction motor is made up of one stator winding and two. The analysis of the single phase motor can be made on the basis of two theories. Revolving field theory is used for the analysis of behavior of single phase induction motor. 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. Two theories have been suggested to find the performance of a single phase induction motor. Dynamic modeling of singlephase induction motor loads. Refer back to this diagram as the operational requirements of the single phase motor are discussed. To overcome this drawback and make the motor selfstarting, it is temporarily converted into a two phase motor during starting period.
The double field revolving theory states that, any alternating quantity can be resolved into two rotating components, which rotate in opposite directions and each having a magnitude as half of the. The stator carries a distributed winding in the slots cut around the inner periphery. Single phase induction motor double revolving field theory a singlephase ac current supplies the main winding that produces a pulsating magnetic field. Apr 25, 2018 revolving field theory is used for the analysis of behavior of single phase induction motor. In case of single phase induction motors, the stator winding produces an alternating magnetic field having maximum magnitude of. A single phase ac supply is given to the stator of single phase induction motor. The single phase induction motor is much the same in construction as the three phase motor. Since single phase induction motor loads make up a signi cant portion of some power systems, it is important to develop accurate models for use in stability studies. The stator winding is excited by the single phase a. Equivalent circuit of a single phase induction motor 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. This theory makes use of the idea that an alternating uniaxial quantity can be represented by two oppositelyrotating vectors of half magnitude. The rotor connects the mechanical load through the shaft. The field polarity reverses twice in each cycle but the field does not rotate. Operating principle the single phase induction motor operation can be described by two methods.
Basic theories there are two basic theories which explain why a torque is produced in the rotor once it is turning. Working principle of a single phase induction motor circuit globe. A singlephase ac current supplies the main winding that produces a pulsating magnetic field. The rotor will constantly be turning to align its magnetic field with that of the stator field. The double revolving field theory can be effectively used to obtain the equivalent circuit of a single phase induction motor. Well, a single phase induction motor with its main winding alone can be represented as shown in figure below. Double revolving field theory a singlephase ac voltage supplies the main winding that produces a magnetic field change with time around one access so that this field call as pulsating.
The basic idea behind the double field revolving theory is that any alternating quantity can be resolved into 2 equal components rotating in opposite direction. The single phase induction motor circuit is given by double revolving field theory which states that a stationary pulsating magnetic field might be resolved into two rotating fields, both having equal magnitude but opposite in direction. What is the double revolving field theory for a single. Single phase induction machines are commonly found in many household appliances. This can be considered to generate two counter rotating magnetic fields, as shown in figure 1a. Double revolving field theory of single phase induction motor. This may be achieved by converting a single phase supply into two phase supply through the use of an additional winding. In this video concept of double revolving field theory, main winding. A given data of single phase induction motor is taken from laboratory and its equivalent circuit is obtained through the double revolving theory. This type of motor normally have two stator windings. The induction motor responds to each magnetic field.
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