Ac electric motor

AC ELECTRIC MOTORS

Working principle
AC motor can be a device which converts alternating electric current into a mechanical device by using an electromagnetic induction phenomenon. The AC motor contains two basic parts another stationary stator having coils supplied with an alternating current to make a rotating magnetic field and an internal rotor attached to the output shaft making a second rotating magnetic field.

The rotor can be an electric conductor which is suspended in the magnetic field. hzpt motor Because the rotor is continually rotating there is a change in magnetic field. According to the Faraday’s regulation, this change in magnetic field induces an electric current in the rotor.

Types of AC Electrical Motor
The AC motors could be basically classified into two categories, synchronous, and asynchronous motors
Synchronous Motor
These motors operate at a synchronous quickness and convert AC electrical power into the mechanical power.
When the energy supply is applied to 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. Consequently, 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 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 creates a magnetic field which rotates at a rate 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 upon the rotor and for another second, they trigger an attractive drive. But rotor continues to be in standstill condition because of its high inertial moment. Therefore, the synchronous engine 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.
Compared to an induction motor, this operates at higher efficiencies at lower speeds
Disadvantages

It is not self-starting. It requires some arrangement for beginning and synchronizing.
Since its starting torque is zero, it cannot be started while having a load
It can’t 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 since it always runs at a speed lower 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 engine, the single armature winding acts both as an armature winding in addition to a field winding. The flux is definitely produced in the air gap whenever the stator winding comes to the Air Gap. This flux will rotate at a fixed speed. Therefore, it’ll 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 electric motor, an alternating flux will be produced. This flux rotates at an asynchronous acceleration 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 developed in the rotor conductor. A rotor current is definitely 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 may be 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 decrease the relative velocity.

The speed of rotating magnetic field is distributed by

DC motor

Single phase induction Motor
AC electric engine which utilizes one phase power supply is named single phase induction motor.it is commonly found in the domestic and industrial application.it consists of stator and Rotor part. A single-phase power is directed at the stator winding. A squirrel cage rotor laminated with the iron core 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 engine is attached to the mechanical load by using the shaft. Due to the rotating flux in the stator, an alternating electromagnetic field is induced in the rotor. But this alternating flux didn’t provide needed rotation to the rotor. That is why the single phase motors aren’t self-starting.

To be able to achieve self-beginning convert this single phase motor right into a two-phase engine 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 kind of motor is named three-phase induction motor. Just like 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-phase 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 quickness. This rotating magnetic field induced an EMF in the rotor which in turn produced an induced current which flows in a direction 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 fits no torque will produce

Advantages

Simple and rugged construction
High efficiency and great power factor
Minimum maintenance
Self-starting motor.
Disadvantages

Speed decreases with upsurge in load
Speed control is difficult
Having poor beginning torque and high hurry current.
Application

Large capacity exhaust fans
Driving lathe machines
Crushers