Ac electric motor

AC ELECTRIC MOTORS

Working principle
AC motor can be a device which converts alternating current right into a mechanical device by using an electromagnetic induction phenomenon. The AC motor includes two basic parts another stationary stator having coils given an alternating current to make a rotating magnetic field and an internal rotor mounted on the output shaft producing another rotating magnetic field.

The rotor can be an electric conductor which is suspended in the magnetic field. Since the rotor is constantly rotating there exists a alter in magnetic field. According to the Faraday's legislation, this modify in magnetic field induces a power 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 swiftness and convert AC electrical energy in to the mechanical power.
When the power supply is put on the synchronous electric motor, a revolving field is set up. This field attempts to drag the rotor towards it but because of the inertia of the rotor, it cannot do it. So, there will be no starting torque. As a result, the synchronous motor is not a self-starting motor.

Principles of operation

This motor has two electrical inputs. One is the stator winding which is supplied by a 3-phase 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-phase finding produces a magnetic field which rotates at a speed called synchronous speed.

When rotor and stator begin rotating, at some time the rotor and stator have the same polarity leading to a repulsive force on the rotor and for the next second, they cause an attractive push. But rotor remains in standstill condition due to its high inertial instant. Therefore, the synchronous engine is not self-starting.

Advantages

The motor speed is constant irrespective of the load.
Electromagnetic power of the synchronous motor varies linearly with the voltage.
In comparison to an induction motor, it operates in higher efficiencies at decrease speeds
Disadvantages

It is not self-starting. It requires some arrangement for starting and synchronizing.
Since its beginning torque is zero, it cannot be started whilst having a load
It cannot 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 less than the synchronous speed. The induction motor could be classified into primarily two sub-classes. 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 definitely produced in the atmosphere gap whenever the stator winding is supplied to the Air Gap. This flux will rotate at a set speed. Therefore, it'll induce a voltage in the stator and the rotor winding.
The current 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 electric motor, an alternating flux will be produced. This flux rotates at an asynchronous quickness and this flux is called the rotating magnetic field. Due to the relative speed between your stator RMF and rotor conductor, an hzpt motor induced EMF is definitely created in the rotor conductor. A rotor current can be then produced due to this induced EMF.

This induced current lags behind the stator flux.

The direction of the induced current is in such a way 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 path 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 motor which utilizes single phase power supply is named single phase induction engine.it is commonly used in the household and industrial application.it includes stator and Rotor component. A single-phase power is given to the stator winding. A squirrel cage rotor laminated with the iron primary is connected to a mechanical load with the help 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 electric motor 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 definitely induced in the rotor. But this alternating flux did not provide needed rotation to the rotor. This is why the solitary phase motors aren't self-starting.

In order to achieve self-beginning convert this solitary phase motor right into a two-phase engine 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
Whenever a three-phase supply is connected to the stator winding, this type of motor is named three-phase induction motor. As being a single phase electric motor, it has also 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 acceleration.
Working principle

When AC supply is directed at the 3-phase winding of the stator, it produces an alternating flux which revolves with synchronous velocity. This rotating magnetic field induced an EMF in the rotor which in turn created an induced current which flows in a path which reverse that of the rotating magnetic field, create a torque in the rotor. The swiftness of the rotor will not be identical to that of the stator. If acceleration fits 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