AC ELECTRIC MOTORS
Working principle
AC motor is a device which converts alternating electric current into a mechanical device through the use of an electromagnetic induction phenomenon. The AC motor includes two basic parts an outside stationary stator having coils supplied with an alternating current to produce a rotating magnetic field and an inside rotor attached to the output shaft generating another rotating magnetic field.
The rotor is an electric conductor which is suspended inside a magnetic field. Since the rotor is continually rotating there is a alter in magnetic field. Based on the Faraday’s law, this alter in magnetic field induces an electric current in the rotor.
Types of AC Electric Motor
The AC motors can be basically classified into two categories, synchronous, and asynchronous motors
Synchronous Motor
These motors operate at a synchronous velocity and convert AC electrical power into the mechanical power.
When the power supply is put on the synchronous motor, a revolving field is established. This field attempts to drag the rotor towards it but because of the inertia of the rotor, it cannot perform 
it. So, there will be no hzpt motor starting torque. Consequently, 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-phase 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 constant flux. The 3-stage finding creates a magnetic field which rotates at a velocity called synchronous speed.
When rotor and stator begin rotating, at some time the rotor and stator have the same polarity causing a repulsive force upon the rotor and for the next second, they cause an attractive pressure. But rotor continues to be in standstill condition due to its high inertial moment. Therefore, the synchronous engine is not self-starting.
Advantages
The motor speed is constant irrespective of the strain.
Electromagnetic power of the synchronous engine varies linearly with the voltage.
In comparison to an induction motor, it operates at higher efficiencies at decrease speeds
Disadvantages
It is not self-starting. It needs some arrangement for beginning and synchronizing.
Since its starting torque is zero, it cannot be started whilst having a load
It can’t be used for applications which require frequent starting so 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 less than the synchronous speed. The induction motor could be classified into primarily two sub-categories. The single-phase induction engine and the 3-phase induction motor.
In an induction motor, the single armature winding acts both as an armature winding in addition to a field winding. The flux is usually produced in the atmosphere gap whenever the stator winding is supplied to the Surroundings Gap. This flux will rotate at a set 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 in an induction electric motor, an alternating flux will be produced. This flux rotates at an asynchronous swiftness and this flux is known as the rotating magnetic field. Due to the relative speed between your stator RMF and rotor conductor, an induced EMF is created in the rotor conductor. A rotor current is then produced because of this induced EMF.
This induced current lags behind the stator flux.
The direction of the induced current is in such a way that it will oppose the foundation of its production. The foundation of the production may be the relative velocity between rotor stator flux and rotor. The rotor will try to rotate in the same direction as a stator in order to decrease the relative velocity.
The speed of rotating magnetic field is distributed by
DC motor
Single phase induction Motor
AC electric electric motor which utilizes one phase power supply is named single phase induction engine.it is commonly used in the household and industrial application.it includes stator and Rotor part. A single-phase power is directed at the stator winding. A squirrel cage rotor laminated with the iron primary is linked to a mechanical load with the help of the shaft.
Principle of operation
When the single-phase supply is given to the stator winding an alternating flux will produce in the stator winding.
A squirrel cage engine is attached to the mechanical load with the aid of the shaft. Because of the rotating flux in the stator, an alternating electromagnetic field is induced in the rotor. But this alternating flux didn’t provide necessary rotation to the rotor. That is why the one phase motors aren’t self-starting.
To be able to achieve self-starting convert this solitary phase motor right into a two-phase motor for temporarily. This can 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 linked to the stator winding, this type of motor is named three-phase induction motor. Just like a single phase engine, it has additionally both stator and rotor winding. The stator wounded by a 3-stage winding supplied by a 3-stage supply produces an alternating flux which rotates at a synchronous quickness.
Working principle
When AC supply is given to the 3-phase winding of the stator, it produces an alternating flux which revolves with synchronous speed. This rotating magnetic field induced an EMF in the rotor which in turn created an induced current which flows in a path which opposite that of the rotating magnetic field, produce a torque in the rotor. The velocity of the rotor will never be identical to that of the stator. If velocity matches no torque will produce
Advantages
Simple and rugged construction
High efficiency and great power factor
Minimum maintenance
Self-starting motor.
Disadvantages
Speed decreases with increase in load
Speed control is difficult
Having poor starting torque and high hurry current.
Application
Large capacity exhaust fans
Driving lathe machines
Crushers