AC ELECTRIC MOTORS
Working principle
AC motor is certainly a device which converts alternating electric current into a mechanical device through the use of an electromagnetic induction phenomenon. The AC motor contains two basic parts an outside stationary stator having coils supplied with an alternating current to produce a rotating magnetic field and an internal rotor mounted on the output shaft producing a second rotating magnetic field.
The rotor is an electric conductor which is suspended in the magnetic field. Because the rotor is constantly rotating there is a alter in magnetic field. Based on the Faraday’s law, this modify in magnetic field induces an electric current in the rotor.
Types of AC Electrical Motor
The AC motors could be basically categorized into two categories, synchronous, and asynchronous motors
Synchronous Motor
These motors operate at a synchronous quickness and convert AC electrical energy in to the mechanical power.
When the energy supply is applied to the synchronous engine, 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, you will see no starting torque. As a result, the synchronous motor isn’t a self-starting motor.
Principles of operation
This motor has two electrical inputs. One is the stator winding which is supplied by a 3-stage supply and the various other one is the rotor winding which comes by a DC supply. Thus, two magnetic areas 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 acceleration hzpt motor called synchronous speed.
When rotor and stator begin rotating, at some point the rotor and stator have the same polarity causing a repulsive force upon the rotor and for the next second, they cause an attractive force. But rotor remains in standstill condition because of 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 motor varies linearly with the voltage.
In comparison to an induction motor, it operates at higher efficiencies at reduce speeds
Disadvantages
It is not self-starting. It needs some arrangement for beginning and synchronizing.
Since its beginning torque is zero, it can’t be started while having a load
It cannot be used for applications which require frequent beginning so when self-starting is required.
Application
Dampers
Conveyor systems
Variable transformers
Cryogenic pumps
Induction Motor
The induction motor can be named as Asynchronous not because it always runs at a speed lower than the synchronous speed. The induction motor can be classified into primarily two sub-types. 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 as well as a field winding. The flux is produced in the air gap whenever the stator winding comes to the Atmosphere 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 within an induction motor, an alternating flux will be produced. This flux rotates at an asynchronous speed and this flux is known as the rotating magnetic field. Because of the relative speed between the stator RMF and rotor conductor, an induced EMF is created in the rotor conductor. A rotor current is usually then produced due to this induced EMF.
This induced current lags behind the stator flux.
The direction of the induced current is so that it tends to 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 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 motor which utilizes solitary phase power supply is named single phase induction motor.it is commonly found in the domestic and commercial application.it contains stator and Rotor part. A single-phase power supply is given to the stator winding. A squirrel cage rotor laminated with the iron primary is connected to a mechanical load by using 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 aid of the shaft. Because of the rotating flux in the stator, an alternating electromagnetic field 
In order to achieve self-beginning convert this solitary phase motor right into a two-phase motor for temporarily. This is often 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
Whenever a three-phase supply is linked to the stator winding, this type of motor is called three-phase induction motor. Just like a single phase engine, it has also both stator and rotor winding. The stator wounded by a 3-phase winding supplied by a 3-phase supply creates 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 in turn produced an induced current which flows in a path which opposite that of the rotating magnetic field, create a torque in the rotor. The acceleration of the rotor will not be same as that of the stator. If swiftness 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 upsurge in load
Speed control is difficult
Having poor beginning torque and high rush current.
Application
Large capacity exhaust fans
Driving lathe machines
Crushers