AC ELECTRIC MOTORS
AC motor is a device which converts alternating current right 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 make a rotating magnetic field and an internal rotor attached to the output shaft creating another rotating magnetic field.
The rotor is an electric conductor which is suspended in the magnetic field. Since the rotor is constantly rotating there is a modify in magnetic field. According to the Faraday’s law, this change in magnetic field induces an electric current in the rotor.
Types of AC Electric Motor
The AC motors can be basically categorized into two categories, synchronous, and asynchronous motors
These motors operate at a synchronous rate and convert AC electrical power into the mechanical power.
When the energy supply is applied to the synchronous electric motor, a revolving field is established. This field tries to drag the rotor towards it but due to 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 may be the stator winding which is supplied by a 3-phase supply and the other one is the rotor winding which comes by a DC supply. Thus, two magnetic areas are produced in a synchronous motor.
The 3-phase winding produces 3-phase magnetic flux and rotor winding produce continuous flux. The 3-phase finding generates a magnetic field which rotates at a speed called synchronous speed.
When rotor and stator start rotating, at some time the rotor and stator have the same polarity causing a repulsive force on the rotor and for the next second, they trigger an attractive push. But rotor remains in standstill condition because of its high inertial minute. Therefore, the synchronous motor is not self-starting.
The motor speed is continuous irrespective of the load.
Electromagnetic power of the synchronous engine varies linearly with the voltage.
In comparison to an induction motor, this operates in higher efficiencies at lower speeds
It isn’t self-starting. It needs some arrangement for beginning 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 starting and when self-starting is required.
The induction motor can be named as Asynchronous not since it always runs at a speed less than the synchronous speed. The induction electric motor could be classified into primarily two sub-groups. The single-phase induction engine and the 3-phase induction motor.
In an induction engine, the single armature winding acts both as an armature winding as well as a field winding. The flux can be produced in the atmosphere gap whenever the stator winding comes to the Atmosphere Gap. This flux will rotate at a fixed 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 acceleration and this flux is called the rotating magnetic field. Because of the relative speed between your stator RMF and rotor conductor, an induced EMF is certainly developed in the rotor conductor. A rotor current can be 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 foundation of its production. The source of the production is the relative velocity between rotor stator flux and rotor. The rotor will attempt to rotate in the same direction as a stator to be able to reduce the relative velocity.
The speed of rotating magnetic field is distributed by
Single phase induction Motor
AC electric electric motor which utilizes one phase power supply is named single phase induction engine.it is commonly found in the household and industrial 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 core is linked to a mechanical load by making use 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 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 induced in the rotor. But this alternating flux did not provide necessary rotation to the rotor. That is why the solitary phase motors are not self-starting.
In order to achieve self-beginning convert this single phase motor into a two-phase electric motor for temporarily. This can 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 electric motor, it has additionally 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 given to the 3-phase winding of the stator, it creates an alternating flux which revolves with synchronous quickness. This rotating magnetic field induced an EMF in the rotor which in turn created an induced current which flows in a path which opposite that of the rotating magnetic field, produce a torque in the rotor. The swiftness of the rotor will not be identical to that of the stator. If acceleration matches no torque will produce
Simple and rugged construction
High efficiency and great power factor
hzpt motor Minimum maintenance
Speed decreases with increase in load
Speed control is difficult
Having poor starting torque and high hurry current.
Large capacity exhaust fans
Driving lathe machines