Single-Phase Induction Motor – Construction, Operation & Types of 1-Phase Induction Motors
The single-phase motors are more preferred over a three-phase induction motor for domestic, commercial applications. Because form utility, only single-phase supply is available. So, in this type of application, the three-phase induction motor cannot be used.
in the following post, we will be showing the construction and different types of 1-phase induction motors with working and applications.
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Table of Contents
Construction of Single-Phase Induction Motor
A single phase induction motor is similar to the three phase squirrel cage induction motor except there is single phase two windings (instead of one three phase winding in 3-phase motors) mounted on the stator and the cage winding rotor is placed inside the stator which freely rotates with the help of mounted bearings on the motor shaft.
The construction of a single-phase induction motor is similar to the construction of a three-phase induction motor.
Similar to a three-phase induction motor, single-phase induction motor also has two main parts;
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In stator, the only difference is in the stator winding. The stator winding is single-phase winding instead of three-phase winding. The stator core is the same as the core of the three-phase induction motor.
In a single-phase induction motor, there are two winding are used in stator except in shaded-pole induction motor. Out of these two windings, one winding is the main winding and the second is auxiliary winding.
The stator core is laminated to reduce the eddy current loss. The single-phase supply is given to the stator winding (main winding)
Rotor of single-phase induction motor is the same as a rotor of squirrel cage induction motor. Instead of rotor winding, rotor bars are used and it is short-circuited at the end by end-rings. Hence, it makes a complete path in the rotor circuit. The rotor bars are braced to the end-rings to increase the mechanical strength of the motor.
The rotor slots are skewed at some angle to avoid magnetic coupling. And it also used to make a motor run smooth and quiet.
The following fig shows the stator and rotor of a 1-phase induction motor.
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Working of Single-phase Induction Motor
Single-phase AC supply is given to the stator winding (main winding). The alternating current flowing through the stator winding produces magnetic flux. This flux is known as the main flux.
Now we assume that the rotor is rotating and it is placed in a magnetic field produced by the stator winding. According to Faraday’s law, the current start flowing in the rotor circuit it is a close path. This current is known as rotor current.
Due to the rotor current, the flux produced around the rotor winding. This flux is known as rotor flux.
There are two fluxes; main flux which is produced by stator and second is the rotor flux which is produced by the rotor.
Interaction between main flux and rotor flux, the torque produced in the rotor and it starts rotating.
The stator field is alternating in nature. The speed of the stator field is the same as synchronous speed. The synchronous speed of the motor depends on the number of pole and supply frequency.
It can represent by two revolving fields. These fields are equal in magnitude and rotating in the opposite direction.
Let say Φm is a maximum field induced in the main winding. So, this field is divided into two equal parts and that is Φm/2 and Φm/2.
Out of these two fields, one field Φf is rotating in an anticlockwise direction and the second field Φb is rotating in a clockwise direction. Therefore, the resultant field is zero.
Φr = Φf – Φb
Φr = 0
Now consider the resultant field at different instants.
When a motor starts, two fields are induced as shown in the above figure. These two fields are the same magnitude and opposite direction. So, resultant flux is zero.
In this condition, the stator field cannot cut by rotor field and resultant torque is zero. So, the rotor cannot rotate but it produces humming.
Now consider after the rotation of 90˚, both filed are rotated and pointing in the same direction. Therefore, the resultant flux is a summation of both fields.
Φr = Φf + Φb
Φr = 0
In this condition, the resultant filed is equal to the maximum field induced by the stator. Now, both fields rotate separately and it is alternative in nature.
So, both fields cut by the rotor circuit and EMF induced in the rotor conductor. Due to this EMF, the current starts flowing in the rotor circuit and it induces a rotor flux.
Due to the interaction between stator flux and rotor flux motor continues to rotate. This theory is known as Double Revolving Theory or double field revolving theory.
Now, from the above explanation, we can conclude that the single-phase induction motor is not self-starting.
To make this motor self-starting motor, we need stator flux rotating in nature instead of alternating nature. This can be done by various methods.
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Single-phase induction motor can be classified according to starting methods.
Types of Single-phase Induction Motors
The single-phase induction motors are classified as;
- Split Phase Induction Motor
- Shaded Pole Induction Motor
- Capacitor Start Induction Motor
- Capacitor Start Capacitor Run Induction Motor
- Permanent Capacitor Induction Motor
Split Phase Induction Motor
In this type of motor, an extra winding is wounded on the same core of the stator. So, there are two windings in the stator.
One winding is known as the main winding or running winding and second winding is known as starting winding or auxiliary winding. A centrifugal switch is connected in series with the auxiliary winding.
The auxiliary winding is highly resistive winding and the main winding is highly inductive winding. The auxiliary winding has few turns with a small diameter.
The aim of auxiliary winding is to create a phase difference between both fluxes produced by the main winding and rotor winding.
The connection diagram is as shown in the above figure. The current flowing through the main winding is IM and current flowing through the auxiliary winding is IA. Both windings are parallel and supplied by voltage V.
The auxiliary winding is highly resistive in nature. So, the current IA is almost in phase with supply voltage V.
The main winding is highly inductive in nature. So, the current IM lags behind the supply voltage with a large angle.
The total stator flux is induced by the resultant current of these two winding. As shown in the phasor diagram, the resultant current is represented as (I). It will create a phase difference between fluxes and resultant flux produces a rotating magnetic field. And the motor starts rotating.
Auxiliary winding only uses to start the motor. This winding is not useful in running condition. When the motor reaches 75 to 80 % of synchronous speed, the centrifugal switch opens. So, the auxiliary winding is out from the circuit. And motor runs on only main winding.
The phase difference creates by this method is very small. Hence, the starting torque of this motor is poor. So, this motor is used in low starting torque applications like a fan, blower, grinder, pumps, etc.
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Shaded Pole Induction Motor
As compared to other types of single-phase induction motor, this motor has a different construction and working principle. This type of motor does not require auxiliary winding.
This motor has stator salient pole or projecting pole and the rotor is the same as squirrel cage induction motor. The stator poles are constructed specially to create a rotating magnetic field.
A pole of this motor is divided into two parts; shaded part and un-shaded part. It can be created by cutting pole into unequal distances.
A copper ring is placed in the small part of the pole. This ring is a highly inductive ring and it is known as a shaded ring or shaded band. The part at which shaded ring is paced is known as shaded part of the pole and the remaining part is an unshaded part.
The construction of this motor is as shown in the below figure.
When an alternating supply passing through the stator winding, an alternating flux induced in the stator coil. Due to this flux, some amount of flux will link with shaded ring and current will flow through a shaded ring.
According to Len’z law, the current passing through coil is opposite in nature, and flux produced due to this coil will oppose the main flux.
The shaded ring is a highly inductive coil. So, it will oppose the main flux when both fluxes are in the same direction and it will increase the main flux when both fluxes are in the opposite direction.
So, it will create a phase difference between the main flux (stator flux) and rotor flux. By this method, a phase difference is very less. Hence, the starting torque is very less. It is used in applications like toy motor, fan, blower, record player, etc.
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Capacitor Start Induction Motor
This type of motor is an advanced version of the Split phase induction motor. The disadvantage of split-phase induction is low torque production. Because in this motor, the phase difference created is very less.
This disadvantage compensates in this motor with the help of a capacitor connected in series with auxiliary winding. The circuit diagram of this motor is as shown in the below figure.
The capacitor used in this motor is a dry-type capacitor. This is designed to use with alternating current. But this capacitor is not used for continuous operation.
In this method also, a centrifugal switch is used which disconnects the capacitor and auxiliary winding when the motor runs 75-80% of synchronous speed.
The current through auxiliary will lead the supply voltage by some angle. This angle is more than the angle increased in a split-phase induction motor.
So, the starting torque of this motor is very high compared to the split-phase induction motor. The starting torque of this motor is 300% more than the full load torque.
Due to high starting torque, this motor is used in the applications where high starting torque is required like, a Lath machine, compressor, drilling machines, etc.
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Capacitor Start Capacitor Run Induction Motor
In this type of motor, two capacitors are connected in parallel with series in auxiliary winding. Out of these two capacitors, one capacitor is used only for starting (starting capacitor) and another capacitor is connected permanently with the motor (running capacitor).
The circuit diagram of this figure is as shown in the below figure.
The starting capacitor has high capacitance value and a running capacitor has low capacitance value. The starting capacitor is connected in series with a centrifugal switch that will open when the speed of the motor is 70% of synchronous speed.
During running conditions, both running winding and auxiliary winding connected with motor. The starting torque and efficiency of this motor are very high.
Therefore, this can be used in the application where high starting torque is required like a refrigerator, air conditioner, ceiling fan, compressor, etc.
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Permanent Capacitor Induction Motor
The low-value capacitor is connected constantly with the auxiliary winding. Here, the capacitor has low capacitance.
The capacitor is used to increase the starting torque but it is low compared to the capacitor start induction motor.
The circuit diagram and phasor diagram of this motor is as shown in the below figure.
The power factor and efficiency of this motor are very high and also it has a high starting torque that is 80% of full load torque.
This type of motor is used in the application like an exhaust fan, blower, heater, etc.
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Applications of Single Phase Induction Motors
Single phase motors are not self starting and less efficient than three phase induction motor and available in 0.5HP to 15HP and still they are widely used for multiple purposes such as:
- Refrigerators, freezers and heaters
- Fans, table fans, ceiling fan, exhaust fans, air coolers and water coolers.
- Washing machines
- machine tools
- Type writers, photostats and printers
- Water pumps and submersible
- Drilling machines
- Other Home instrument, equipment and devices etc.
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AC Motors Capacitor Start Capacitor Run Induction Motor Capacitor Start Induction Motor Induction Motor Motors Permanent Capacitor Induction Motor Shaded Pole Induction Motor Single-Phase Induction Motor Split Phase Induction Motor Types of Motors
Single phase induction motors generally have a construction similar to that of a three phase motor: an ac windings is placed on the stator, short-circuited conductors are placed in a cylindrical rotor. The significant difference is, of-course, that there is only a single phase supply to the stator.What is single phase induction motor construction and working principle? ›
A single phase induction motor consists of a single phase winding on the stator and a cage winding on the rotor. When a 1 phase supply is connected to the stator winding, a pulsating magnetic field is produced. In the pulsating field, the rotor does not rotate due to inertia.What are the types of single phase induction motor? ›
This leads to the three main types of single-phase induction motor: shaded-pole, split-phased, and capacitor motors.How many steps are involved in the construction of single phase induction motor? ›
How many steps are involved in the construction of single phase induction motor? Explanation: There are 5 steps in the construction of the single phase induction motor. They are stator, stator windings, rotor, starting switches, electrolytic capacitor.What is the construction of induction motor? ›
Construction of Induction Motor
A three phase Induction motor mainly consists of two parts called as the Stator and the Rotor. The stator is the stationary part of the induction motor, and the rotor is the rotating part.
- Split phase induction motor.
- Capacitor-start induction motor.
- Capacitor-run induction motor.
- Shaded pole induction motor.
Electric motor: A motor is a device which converts electrical energy into mechanical energy. Principle of motor : A motor works on the principle that when a rectangular coil is placed in a magnetic field and current is passed through it. A force acts on the coil which rotates it continuously.What is the function of single phase induction motor? ›
A single phase induction motor requires separate starting circuitry to provide a rotating field to the motor. The normal running windings within such a single-phase motor can cause the rotor to turn in either direction, so the starting circuit determines the operating direction.What is the principle used in electric motor explain the construction and working of? ›
Hint:Electric motor uses the principle of magnetic force on a current carrying conductor. The direction of force depends on the direction of current flow and magnetic field. However, we can fix the magnetic field and create torque on a loop depending on the current flow. That is how electric motors are constructed.What are the two 2 main parts of a single-phase induction motor? ›
The two main components of the single-phase induction motor are the stator and rotor. As you may know and perceive from the name, the Stator is the stationary part of this motor. On the other hand, the rotor is the rotating component of the motor. the single-phase alternating supply reaches to the stator winding.
A 3-phase induction motor includes two essential components namely the stator & the rotor. In this motor, the stationary part is the stator whereas the rotating part is the rotor. In this motor, the load is connected to the shaft. Three-phase armature winding can be wound over the stator.What is the construction of a motor? ›
Construction of an Electric Motor. Two mechanical components of electric motors are the stator, which is fixed and the rotor, which moves. It also has two electrical components, magnets set and an armature, one of them is attached to the stator and the other to the rotor, together making a magnetic circuit.What is the most common type of induction motor? ›
The majority of industrial motors are three-phase AC induction motors due to its reliability and low cost. In this case, the electric current in the stator winding generates a rotating magnetic field that "induces" (hence the name) electric current in the rotor.What are the examples of single-phase motor? ›
Uses: Single-phase motors are used in equipment and machines that are smaller in size and require lower horsepower (for example, one horsepower). This include equipment such as pumps, refrigerators, fans, compressors, and portable drills.What are the different types of induction motor? ›
Single-phase induction motors and three-phase induction motors are the two main types of induction motors. As their names imply, a single-phase induction motor is connected to a 1 phase AC power supply and a three-phase induction motor is provided with 3 phase AC power supply.What is the working principle of different types of motor? ›
The working principle of the electric motor mainly depends on the interaction of magnetic and electric field. The electric motor is mainly classified into two types. They are the AC motor and the DC motor. The AC motor takes alternating current as an input, whereas the DC motor takes direct current.What is the working principle of single phase motor which law? ›
Working Principle of Single-Phase Induction Motor
To understand the working principle, you must understand two crucial facts in physics, Faraday's first and second laws. Faraday's first law states, ' Whenever a conductor is placed in a varying magnetic field, an electromotive force is induced'.
Fleming's Left-Hand rule is used in electric motors.Which magnet is used for construction of electric motor? ›
an electromagnet is used in place of permanent magnet. large number of turns of coil is used. a soft iron core is used on which the coil is wound.What are the 6 parts of an electric motor? ›
- 1) The Rotor. The rotor is the moving part of your electric motor. ...
- 3) The Bearings. ...
- 4) The Windings. ...
- 5) The Air Gap. ...
- 6) The Commutator. ...
- What Do All of These Components Have in Common?
Its low starting torque is typically 25 to 75% of full-load torque. It is a high slip motor with running speed 7 to 10% below synchronous speed, Also, it is very inefficient, usually below 20%. Low initial cost suits shaded-pole motors to low-horsepower or light-duty applications.Why do single-phase motors use capacitors? ›
Some single-phase AC electric motors require a "run capacitor" to energize the second-phase winding (auxiliary coil) to create a rotating magnetic field while the motor is running. Start capacitors briefly increase motor starting torque and allow a motor to be cycled on and off rapidly.Why are single-phase motors not self starting? ›
We can easily conclude that the single-phase induction motors are not self-starting because the produced stator flux is alternating in nature and at the starting, the two components of this flux cancel each other, and hence there is no net torque.What are the two main parts of a single phase induction motor? ›
The two main components of the single-phase induction motor are the stator and rotor. As you may know and perceive from the name, the Stator is the stationary part of this motor. On the other hand, the rotor is the rotating component of the motor. the single-phase alternating supply reaches to the stator winding.What is the construction of 3 phase induction motor? ›
It consists of a steel frame which encloses a hollow cylindrical core. The core of the three phase induction motor is made up of thin laminations of silicon steel to reduce the eddy current and hysteresis losses.What are the characteristics of single phase induction motor? ›
Its low starting torque is typically 25 to 75% of full-load torque. It is a high slip motor with running speed 7 to 10% below synchronous speed, Also, it is very inefficient, usually below 20%. Low initial cost suits shaded-pole motors to low-horsepower or light-duty applications.Which single-phase motor is mostly used? ›
Uses: Single-phase motors are used in equipment and machines that are smaller in size and require lower horsepower (for example, one horsepower). This include equipment such as pumps, refrigerators, fans, compressors, and portable drills.Which capacitor is used in single-phase motor? ›
A motor capacitor such as a start capacitor or run capacitor is an electrical capacitor that alters the current to one or more windings of a single phase AC induction motor to create a rotating magnetic field.What is the most common single-phase motor? ›
Capacitor-Start: The most common single-phase motor used in industrial applications. It is a modified split-phase motor with a capacitor in series with the start winding to provide a start boost. Application include small conveyors, large blowers, pumps, and direct-drives.What is the major difference between 3 phase and single-phase induction motors? ›
A 1-phase induction motor requires single-phase AC supply, whereas a 3-phase induction motor need a source of 3-phase AC supply for its operation. 1-phase induction motors produce low starting torque, whereas 3phase induction motors produce high starting torque.
Construction of an Electric Motor. Two mechanical components of electric motors are the stator, which is fixed and the rotor, which moves. It also has two electrical components, magnets set and an armature, one of them is attached to the stator and the other to the rotor, together making a magnetic circuit.What is the difference between single-phase motor to three-phase motor? ›
One key difference between single-phase vs. three-phase is that a three-phase power supply better accommodates higher loads. Single-phase power supplies are most commonly used when typical loads are lighting or heating, rather than large electric motors. Single-phase systems can be derived from three-phase systems.What are the two types of induction motor? ›
Induction motor rotors may be of two types, wound rotor or squirrel-cage rotor. A wound rotor has windings similar to and wound for the same number of poles as the stator. The rotor windings are connected to insulated slip rings mounted on the rotor shaft.What are the faults in single-phase induction motor? ›
The various faults are over-voltage, under-current, under-voltage, under-current, overload, over-temperature etc. So indentify such faults most important parameters are voltage, current and temperature.