Everyone knows the importance of motor in today’s life. Nowadays, almost not a single function of the motor is possible. The main function of a motor is to convert electric energy into mechanical energy. The motor is classified into two sections. One is an AC motor and the other is a DC motor thus it is classified on the basis of power supply. AC motor and DC motor include different types of motors such as induction motor, reluctance motor, DC shunt, PMDC, stepper, synchronous, etc.
In today’s article, we will see what is induction motor, what are the types of induction motor and what is its application. This is one of the most used motors in the industry. Also called asynchronous motor because this motor operates at a slower speed than synchronous speed. The synchronous speed is nothing but the motion of the rotary magnetic field inside the stator.
What is an Induction Motor?
The motor with amortisseur winding is known only as an induction motor. In most cases, the induction motor from the construction angle of view is the most common electrical machine. This motor works on the principle of induction. The electromagnetic field is induced in the rotor where the rotating magnetic field of the stator intersects the stationary rotor.
The induction machine is the most commonly used motor in commercial industrial, commercial or residential settings. It is a three-phase AC motor characterized as follows.
- Low cost and low maintenance.
- Simple and strong construction.
- High dependence and sufficient prof proficiency.
- No additional starting motor is required and no synchronization is required.
Also Read: What Is Motor Winding | Types Of Motor Winding | Motor Winding Calculation
What are the Basic Parts of an Induction Motor?
The induction motor consists of two main parts one is a stator and the other is the rotor.
The three-phase windings are manufactured by different stampings inside the stator. He is wounded for a different number of poles. Windings are geometrically separated. And is separated by 120 degrees. There are two types of rotors used in induction motor, one is Squirrel cage rotor and the other is Wound rotor.
No DC field current is required to operate the machine. The rotor voltage is induced in the rotor winding instead of being physically connected by wires.
A rotor is a rotating part of an electromagnetic circuit. The most common type of rotor is the squirrel cage rotor. The rotor consists of a cylindrical laminated core with axially parallel slots for carrying the conductor. Each slot has a copper, aluminum, or alloy bar.
The rotor of three-phase induction motors is often indicated as an anchor. The purpose behind this name is the anchor shape of the rotors used inside the initial electrical devices. In electrical devices, the winding of the anchor will be induced by a magnetic field, although the rotor takes this part in three-phase induction motors.
The induction motor has the same physical stator as the synchronous machine with optional rotor development. The induction motor may act as a motor or generator. On the other hand, it is basically used as induction motors.
Working Principle of Induction Motor:
The working principle of the induction motor is that the AC in the rotor of the motor is required to generate the torque received through electromagnetic induction. The result is generated by the rotary magnetic field of the stator winding.
Types of Induction Motor:
Induction motors are classified into two parts based on their power supply, one is a single-phase power supply and the other is a three-phase power supply. A single-phase motor is connected to a single-phase power supply as its name implies. And a three-phase motor is connected to a three-phase power supply. This motor is then again classified into sub-categories. Single phase-type motors are classified into four types. While three-phase motors are classified into two types.
Single-phase Induction Motor:
The single-phase induction motor is not self-starting and the main winding carries alternating current when it is connected to single-phase power. It is logical that the least expensive, least regular sort engine should be used most regularly.
These are different types depending on the way they started. As this is not self-initiating. It has a split phase, shaded pole, and capacitor motors. Again the capacitor motors are the capacitor start, the capacitor run, and the permanent capacitor motor.
In such motors, a series capacitor or centrifugal switch is used in the starting winding while the supply voltage is applied. The current in the main winding is then damaged in the supply voltage due to the main winding barrier. And initially, the winding current keeps the supply voltage behind depending on the impedance of the starting mechanism.
The angle difference between the two windings is sufficient for the phase to provide a field of rotating dimension to generate the starting torque. When the motor reaches the point at 70% to 80% synchronous speed, the centrifugal switch on the motor shaft opens and disconnects the initial winding.
Types of Single-Phase Induction Motor:
Single-phase induction motors are classified into four types as follows:
|Sr. No.||Types of Single-Phase Induction Motor|
|#1.||Split Phase Induction Motor|
|#2.||Capacitor Start Induction Motor|
|#3.||Capacitor Start & Capacitor Run Induction Motor|
|#4.||Shaded Pole Induction Motor|
#1. Split Phase Induction Motor:
Another name for Split Phase Induction Motor is Resistance Start Motor. Such a motor includes a stator and a single cage rotor. This includes stator two windings called starting windings as well as main windings. These two windings are moved 90 degrees inside the space. Initial winding involves a low induction reaction and high resistance. While winding involves low resistance and high inductive reaction.
The low cost of this type of motor is suitable for loads. Which starts very easily. In which the initial frequency can be controlled. This motor is not used for drives that do not exceed 1 kW due to low starting torque. The application of this motor is mainly in the washing machines, floor polishers, mixer grinders, AC fans, blowers, centrifugal pumps, drilling and lathe machine, etc.
#2. Capacitor Start Induction Motor:
Capacitor Start Induction Motor is a single-phase motor in which a stator and a single cage rotor are used. This stator consists of two windings known as main winding and auxiliary winding. Auxiliary windings are also commonly referred to as starting windings. In motor construction, the alignment of these two windings can be separated by 90 degrees in space.
- This motor is used in places where high starting loads require frequent start-ups.
- This motor is used to operate compressors, pumps, machine tools, and conveyors.
- It is also used in AC compressors and refrigerators.
#3. Capacitor Start & Capacitor Run Induction Motor:
Capacitor Run Induction Motor Working principle is similar to the start capacitor induction motor. We all know that the induction motor is not a self-starting motor. Because the magnetic field generated is not rotary type. Therefore in order to generate a rotary magnetic field, induction motors need a phase difference.
In a split-phase induction motor, this motor however must have resistance to make a phase difference; The capacitor will make a phase difference. This is due to the fact that the current flowing in the capacitor guides the voltage. Capacitor start and capacitor start run type motor have two windings like main and starting.
There is a link inside the capacitor when starting the winding thus the current supply inside the capacitor guides the voltage applied by some angle. Both these motors have high starting torque. That is why this motor is used in conveyors, grinders, compressors, air conditioners, etc.
#4. Shaded Pole Induction Motor:
This is a self-starting single-phase induction type motor. One of these poles can be shed through a copper ring which is also called a shed ring. The function of this ring is similar to secondary winding in a motor. This motor only rotates in a specific way and the opposite speed of this motor is not possible.
The loss of electricity in this motor is very high. The power factor is low. And the induced starting torque can also be very low. The efficiency of this motor is poor due to its low design and low power ratings. This induction motor is used in small devices like fans, relays. Due to its easy start and low cost.
Shaded Pole Induction Motor is used in the hairdryer, exhaust fan, table fan cooling fans, projector, refrigeration device, record player, tape recorder, etc.
Applications of Single-Phase Induction Motor:
The application of a Single-Phase Induction Motor is done in a low-power machine. Which are widely used in industrial and home use. Some of whose applications are as follows.
- Small fans.
- High-speed vacuum cleaners.
- Electric shavers.
- Drilling machines.
Also Read: Difference Between AC Motor And DC Motor
Three-Phase Induction Motor:
A three-phase induction motor is a self-starting motor in which no capacitor, winding start, centrifugal switch, or any other type of starting device is used. This motor is widely used in industrial and commercial applications.
There are two types of three-phase induction motors. squirrel cage and slip ring motors. The squirrel cage motor is widely used due to its rugged construction and simple design. Sleep ring motors require external resistance with a high starting torque.
Induction motors are widely used in industrial, commercial, and household appliances. Because it is hard to build. It does not require much maintenance. They are relatively inexpensive, and only the stator needs a supply.
Types of 3 Phase Induction Motor:
This motor also consists of two main parts like stator and rotor like any other motor. Thus the stator is stationary and the rotor is the rotating part of the motor. The load is connected to this rotor. Three-phase armature winding on the stator can be injured. Once the 3-phase current supply during this winding is balanced, a static amplitude rotary magnetic field can be formed inside the air constantly.
This armature winding is connected to a three-phase power supply and carries a load current. This motor is classified into two types.
|Sr. No.||Types of 3 Phase Induction Motor|
|#1.||Squirrel Cage Induction Motor|
|#2.||Wound Rotor or Slip Ring Induction Motor|
#1. Squirrel Cage Induction Motor:
The construction of the Squirrel Cage Induction Motor is quite simple. The rotor of this motor contains a cylindrical core. Which can be laminated and includes some slots on the outer periphery. These slots are not comparable and are twisted by some angles.
This slot helps prevent magnetic locking between the teeth of the stator and the rotor. So that this can achieve smooth operation. And noise can be reduced. These motors include bar rotors instead of rotor windings where these bars are made of brass, aluminum otherwise copper.
This motor has an aluminum bar in the rotor winding. Otherwise, the insulated copper is fixed in the semi-closed rotor slot. The conductor to both ends of this motor is transmitted shortly by a final ring of the same material. As a result, this type of rotor looks like a squirrel cage hence it is called a squirrel cage induction motor.
#2. Wound Rotor or Slip Ring Induction Motor:
Another name for a sleep ring induction motor is the Wound Rotor motor. The rotor of this motor consists of a laminated cylindrical core. Similar to squirrel cages, there are several slots on the outer circumference. The rotor winding is arranged inside this slot.
In a wound rotor, the insulated windings wound at the top of the rotor like a stator. The winding of this rotor can be evenly distributed. And is usually attached to the STAR model. This can be taken during the three-terminal slip ring of the STAR connection. Hence the reason why this motor is called a slip ring induction motor.
Why 3-Phase Induction Motor is Self Starting?
A three-phase motor has 3 single-phase lines with a phase difference of 120°. That is why the rotary magnetic field involves the same phase difference. So this phase difference will rotate the rotor.
For example, to understand us we take R, Y, and B as three phases. Once the ‘R’ is magnetized, the rotor phase will move towards ‘R’. In the next phase Y will magnetize, so it will magnetize the rotor and after that phase ‘B’. In this way, the rotor will rotate continuously.
Also Read: Double Cage Rotor of Induction Motor
Why 1-Phase Induction Motor is not Self Starting?
The power given to the single-phase induction motor is also single phase. So this produces a pulsating magnetic field, not rotating. A current is generated in the conductor due to the current which is determined in two components. Where each component will rotate in the opposite direction at the same speed.
Thus the net flow will be zero. The flow of induced current in the rotor conductor will be zero and the torque will also be zero. As a result, this motor is not self-starting.
To overcome this problem and make this motor self-starting it can be temporarily converted to a 2-phase motor at the start. For this reason, the stator of a single-phase motor is provided by an additional winding with a finished winding similar to the main winding. Therefore, these windings are located in the 1-phase supply.
The winding can be adjusted. So that the phase difference between the flows inside the two stator windings is very large. Thus this motor acts as a two-phase. Both produce current rotating flux which will make the single-phase motor self-starting.
Advantages of Induction Motor:
This has many advantages depending on the motor construction and the power given to it, some of which are as follows:
|Sr. No.||Advantages of Induction Motor|
|#2.||Low Maintenance Cost|
|#3.||Ease of Operation|
|#5.||High Starting Torque|
#1. Low Cost:
The price of this motor is very low compared to synchronous and DC motors. This is because of its simple and easy design. That is why this motor is used in industrial units, commercial, and households. For fixed speed application and AC line power can be easily connected.
#2. Low Maintenance Cost:
Induction motors are maintenance-free motors compared to DC motors and synchronous. The construction of an induction motor is also easy compared to these two motors. That is why maintenance costs are also low.
#3. Ease of Operation:
The operation of the induction motor is very simple. As it has no rotor electrical connector that supplies power. And the current is induced by the speed of the transformer performance on the rotor due to the low resistance of the rotating coil. Induction motors are self-starting motors. This may result in a reduction in the effort required for maintenance.
#4. Speed Variation:
The speed variation of the induction motor is almost constant. The rate usually varies from a certain load to a certain percentage of the speed.
#5. High Starting Torque:
The starting torque of this motor is very high which is very useful for the operation of the motor. In which the load is applied before starting the motor. Unlike synchronous motors, a three-phase induction motor will have a self-starting torque. However, a single-phase induction motor is not a self-starting one. And made to rotate using some auxiliaries.
Disadvantages of Induction Motor:
Some of the disadvantages of induction motor are as follows:
- The initial torque of the squirrel cage induction motor is not less.
- The motor speed control is not easy.
- This is an unavoidable speed motor and this motor is not applicable where uneven speed is required.
- The power factor is low in the state of light load and it draws a huge current. So copper loss can be high.
Applications of Induction Motor:
Some of the important applications of Induction Motor are as follows:
- Driving lathe machines.
- Oil Mills.
- Textiles and etc.
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