AC ELECTRIC MOTORS
Working principle
AC motor is definitely a device which converts alternating hzpt motor current into a mechanical device by using an electromagnetic induction phenomenon. The AC motor consists of two basic parts an outside stationary stator having coils given an alternating current to produce a rotating magnetic field and an inside rotor attached to the output shaft generating a second rotating magnetic field.
The rotor is an electric conductor which is suspended in the magnetic field. Since the rotor is continually rotating there exists a modify in magnetic field. According to the Faraday’s regulation, this modify in magnetic field induces an electric current in the rotor.
Types of AC Electrical 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 energy into the mechanical power.
When the energy supply is applied to the synchronous engine, a revolving field is set up. This field tries to drag the rotor towards it but due to the inertia of the rotor, it cannot do it. So, you will have no starting torque. Consequently, the synchronous motor is not a self-starting motor.
Principles of operation
This motor has two electrical inputs. One is the stator winding which comes by a 3-stage supply and the other one is 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-phase finding generates a magnetic field which rotates at a quickness called synchronous speed.
When rotor and stator begin rotating, at some point the rotor and stator have the same polarity causing a repulsive force on the rotor and for another second, they cause an attractive push. But rotor continues to be in standstill condition due to its high inertial moment. Therefore, the synchronous electric motor is not self-starting.
Advantages
The motor speed is continuous irrespective of the strain.
Electromagnetic power of the synchronous electric motor varies linearly with the voltage.
In comparison to an induction motor, this operates at higher efficiencies at reduce speeds
Disadvantages
It is not self-starting. It needs some arrangement for starting 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 beginning 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 less than the synchronous speed. The induction engine could be classified into mainly two sub-classes. The single-phase induction engine and the 3-stage induction motor.
In an induction motor, the single armature winding acts both as an armature winding in addition to a field winding. The flux can be produced in the atmosphere gap whenever the stator winding is supplied to the Surroundings 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 in an induction electric motor, an alternating flux will be produced. This flux rotates at an asynchronous rate and this flux is called the rotating magnetic field. Due to the relative speed between your stator RMF and rotor conductor, an induced EMF can be 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 in such a way that it will oppose the source 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 path as a stator to be able to reduce the relative velocity.
The speed of rotating magnetic field is given by
DC motor
Single phase induction Motor
AC electric motor which utilizes one phase power supply is named single phase induction motor.it is commonly used in the household and industrial application.it consists of stator and Rotor 
part. A single-phase power supply is directed at the stator winding. A squirrel cage rotor laminated with the iron core is connected 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 mounted on the mechanical load by making use of the shaft. Due to the rotating flux in the stator, an alternating electromagnetic field can be induced in the rotor. But this alternating flux didn’t provide necessary rotation to the rotor. That is why the single phase motors aren’t self-starting.
In order to achieve self-beginning convert this solitary phase motor into a two-phase electric motor for temporarily. This could be achieved 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
Whenever a three-phase supply is linked to the stator winding, this type of motor is called three-phase induction motor. As being a single phase motor, it has additionally both stator and rotor winding. The stator wounded by a 3-stage winding supplied by a 3-phase supply generates an alternating flux which rotates at a synchronous speed.
Working principle
When AC supply is given to the 3-phase winding of the stator, it produces an alternating flux which revolves with synchronous rate. This rotating magnetic field induced an EMF in the rotor which produced an induced current which flows in a path which opposite that of the rotating magnetic field, create a torque in the rotor. The velocity of the rotor will never be same as 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 hurry current.
Application
Large capacity exhaust fans
Driving lathe machines
Crushers