AC ELECTRIC MOTORS
AC motor is certainly a device which converts alternating electric current into a mechanical device through the use of an hzpt motor electromagnetic induction phenomenon. The AC motor includes two basic parts another stationary stator having coils supplied with an alternating current to produce a rotating magnetic field and an inside rotor mounted on the output shaft creating another rotating magnetic field.
The rotor is an electric conductor which is suspended inside a magnetic field. Because the rotor is continually rotating there exists a change in magnetic field. Based on the Faraday’s regulation, this change in magnetic field induces a power current in the rotor.
Types of AC Electric Motor
The AC motors could be basically classified into two categories, synchronous, and asynchronous motors
These motors operate at a synchronous speed and convert AC electrical power into the mechanical power.
When the energy 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 isn’t 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 may be the rotor winding which is supplied 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 start rotating, at some time the rotor and stator have the same polarity leading to a repulsive force on the rotor and for another second, they trigger an attractive force. But rotor continues to be in standstill condition due to its high inertial minute. Therefore, the synchronous electric motor is not self-starting.
The motor speed is constant irrespective of the strain.
Electromagnetic power of the synchronous motor varies linearly with the voltage.
Compared to an induction motor, it operates at higher efficiencies at decrease speeds
It is not self-starting. It requires some arrangement for starting and synchronizing.
Since its starting torque is zero, it can’t be started whilst having a load
It cannot be used for applications which require frequent beginning and when self-starting is required.
The induction motor can be 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 electric motor and the 3-stage induction motor.
In an induction engine, the single armature winding acts both as an armature winding as well as a field winding. The flux is definitely produced in the air flow gap whenever the stator winding is supplied to the Air flow Gap. This flux will rotate at a set speed. Therefore, it will 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 motor, an alternating flux will be produced. This flux rotates at an asynchronous speed and this flux is known as the rotating magnetic field. Due to the relative speed between the stator RMF and rotor conductor, an induced EMF is usually created in the rotor conductor. A rotor current is then produced for this reason 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 foundation 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
Single phase induction Motor
AC electric electric motor which utilizes one phase power supply is called single phase induction engine.it is commonly found in the domestic and commercial application.it includes stator and Rotor component. 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 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 mounted on the mechanical load by using the shaft. Because of the rotating flux in the stator, an alternating electromagnetic field is certainly induced in the rotor. But this alternating flux didn’t provide necessary rotation to the rotor. That is why the solitary phase motors aren’t self-starting.
To be able to achieve self-beginning convert this solitary phase motor into a two-phase electric motor for temporarily. This could be attained by introducing a starting winding
Fewer substations required
Cannot handle the overload
No uniform Torque
High insulation cost
Three Phase Induction Motor
Whenever a three-phase supply is linked to the stator winding, this type of motor is named three-phase induction motor. As being a single phase engine, it has also both stator and rotor winding. The stator wounded by a 3-phase winding given by a 3-phase supply generates an alternating flux which rotates at a synchronous acceleration.
When AC supply is directed at the 3-phase winding of the stator, it generates 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 reverse that of the rotating magnetic field, create a torque in the rotor. The rate of the rotor will never be identical to that of the stator. If acceleration matches no torque will produce
Simple and rugged construction
High efficiency and great power factor
Speed decreases with upsurge in load
Speed control is difficult
Having poor starting torque and high hurry current.
Large capacity exhaust fans
Driving lathe machines