AC ELECTRIC MOTORS
Working principle
AC motor is certainly a device which converts alternating current into a mechanical device through the use of an electromagnetic induction hzpt motor phenomenon. The AC motor consists of two basic parts another stationary stator having coils supplied with an alternating current to make a rotating magnetic field and an inside rotor mounted on the output shaft making another rotating magnetic field.
The rotor is an electric conductor which is suspended in the magnetic field. Since the rotor is continually rotating there is a change in magnetic field. According to the Faraday’s law, this modify in magnetic field induces a power current inside a rotor.
Types of AC Electric Motor
The AC motors can be basically categorized into two categories, synchronous, and asynchronous motors
Synchronous Motor
These motors operate at a synchronous acceleration and convert AC electrical power into the mechanical power.
When the energy supply is put on the synchronous engine, a revolving field is established. This field tries to drag the rotor towards it but because of the inertia of the rotor, it cannot perform it. So, you will have no starting torque. Because of this, the synchronous motor isn’t a self-starting motor.
Principles of operation
This motor has two electrical inputs. One may be the stator winding which comes by a 3-stage supply and the other one may be the rotor winding which comes by a DC supply. Thus, two magnetic fields are stated in a synchronous motor.
The 3-phase winding produces 3-phase magnetic flux and rotor winding produce continuous flux. The 3-stage finding produces a magnetic field which rotates at a swiftness called synchronous speed.
When rotor and stator start rotating, at some point the rotor and stator have the same polarity leading to a repulsive force upon the rotor and for the next second, they trigger an attractive power. But rotor remains in standstill condition due to its high inertial minute. Therefore, the synchronous electric motor is not self-starting.
Advantages
The motor speed is continuous irrespective of the strain.
Electromagnetic power of the synchronous motor varies linearly with the voltage.
Compared to an induction motor, this operates at higher efficiencies at reduced speeds
Disadvantages
It is not self-starting. It requires some arrangement for beginning and synchronizing.
Since its starting torque is zero, it can’t be started whilst having a load
It can’t be used for applications which require frequent starting and when self-starting is required.
Application
Dampers
Conveyor systems
Variable transformers
Cryogenic pumps
Induction Motor
The induction motor is also named as Asynchronous not because it always runs at a speed lower than the synchronous speed. The induction engine can be classified into primarily two sub-types. The single-phase induction electric motor and the 3-phase induction motor.
In an induction engine, the single armature winding acts both as an armature winding in addition to a field winding. The flux is produced in the atmosphere gap whenever the stator winding is supplied to the Atmosphere Gap. This flux will rotate at a fixed speed. Therefore, it will induce a voltage in the stator and the rotor winding.
The existing flow through the rotor winding reacts with the rotating flux and produces the torque.
Basic Working Principle
When an AC supply is fed to the stator winding within an induction engine, an alternating flux will be produced. This flux rotates at an asynchronous velocity and this flux is known as the rotating magnetic field. Due to the relative speed between the stator RMF and rotor conductor, an induced EMF is usually created in the rotor conductor. A rotor current is certainly then produced for this reason induced EMF.
This induced current lags behind the stator flux.
The direction of the induced current is so that it tends to oppose the foundation of its production. The source of the production is the relative velocity between rotor stator flux and rotor. The rotor will try to rotate in the same direction as a stator to be able to reduce the relative velocity.
The speed of rotating magnetic field is distributed by
DC motor
Single phase induction Motor
AC electric engine which utilizes single phase power supply is called single phase induction engine.it is commonly used in the domestic and industrial application.it includes stator and Rotor part. A single-phase power supply is directed at the stator winding. A squirrel cage rotor laminated with the iron primary is connected to a mechanical load with the aid of the shaft.
Principle of operation
When the single-phase supply is directed at the stator winding an alternating flux will produce in the stator winding.
A squirrel cage motor is mounted on 
the mechanical load with the help of the shaft. Because of the rotating flux in the stator, an alternating electromagnetic field is certainly induced in the rotor. But this alternating flux did not provide required rotation to the rotor. That is why the single phase motors are not self-starting.
In order to achieve self-beginning convert this single phase motor right into a two-phase electric motor for temporarily. This could be attained by introducing a starting winding
Advantages
Lightweight
Efficient transmission
Fewer substations required
Disadvantages
Cannot handle the overload
No uniform Torque
High insulation cost
Application
Refrigerator
Pumps
Compressor
Portable drills
Three Phase Induction Motor
When a three-phase supply is connected to the stator winding, this kind of motor is named three-phase induction motor. As being a single phase motor, it has also both stator and rotor winding. The stator wounded by a 3-stage winding given by a 3-phase supply generates an alternating flux which rotates at a synchronous quickness.
Working principle
When AC supply is directed at the 3-phase winding of the stator, it creates an alternating flux which revolves with synchronous velocity. This rotating magnetic field induced an EMF in the rotor which in turn produced an induced current which flows in a direction which reverse that of the rotating magnetic field, produce a torque in the rotor. The speed of the rotor will not be identical to that of the stator. If speed matches no torque will produce
Advantages
Simple and rugged construction
High efficiency and good power factor
Minimum maintenance
Self-starting motor.
Disadvantages
Speed decreases with increase in load
Speed control is difficult
Having poor beginning torque and high rush current.
Application
Large capacity exhaust fans
Driving lathe machines
Crushers