Maybe you never thought about the multitude of applications that electric motors have, there are many pieces of equipment, devices, toys and machines that the motors are present in, for example in drills, hair clippers, microwaves, watches, refrigerators, computers , printers, vacuum cleaners, remote control carts, elevators, lathes, escalators, among others.
Such is the importance of electric motors, that we decided to show in this article especially what the three-phase electric motor is, how an electric motor works, the main characteristics of a three-phase motor and its applications, come on a person!
What are electric motors:
Electric motors are machines that have the ability to convert electrical energy into mechanical energy. The motors combine the advantages of electric power with low cost, ease of transport, cleanliness and simplicity of control. Induction motors have an apparently simple construction and their costs are reduced, such as maintenance, manufacture and assembly, as well as easy adaptation to loads of different types.
We can separate the motors by a multitude of characteristics, but the determining factor, which differentiates the motor classes is their energy source, as there are motors that operate with direct current and others with alternating current, and some can use both currents in certain situations, in addition, there are single-phase motors and finally three-phase motors.
Before understanding what a three-phase electric motor is and how it works, it is good to highlight what exactly a three-phase distribution system.
A three-phase system is the most common way to obtain the generation, transmission, and distribution of electrical energy in alternating current. This system incorporates the use of three balanced sine waves, which have a 120-degree difference between them so that the system is balanced.
It is important to highlight that the supply of a three-phase system is made by 4 cables, one neutral and the other three-phase cables (R, T, and S). This type of system is used for installations or loads that demand more power.
Alternating current (AC) motors, which are also known as three-phase asynchronous motors or induction motors, are the most used motors, due to a series of advantages, such as the low cost of maintenance, assembly, manufacture and simplicity in relation to direct current motors, and due to the distribution of electrical energy in the installations being made in alternating current.
Three-phase motors are easily found within industries, such as inside a lathe, milling machine, conveyor belt and various other machines, but outside of industries, we can find a three-phase motor in an elevator or on the escalator for example.
In order to clarify the understanding of how three-phase induction motors work, it is important to know a little about some parts of the motor, which in this case are the rotor and the stator.
- The rotor is everything that rotates around its own axis, in order to produce rotational movements. Rotors are present in any rotating machine, such as turbines and compressors.
- On the other hand, the stator is the part of an electric motor or generator that remains attached to the motor frame and has the function of conducting the magnetic flux. As in the coils, a magnetic field is formed in the rotor capable of inducing an electric current.
Operation and characteristics of three-phase motors.
The working principle for the induction motor is based on the creation of a rotating magnetic field, or rotating field. This rotating field arises from the application of alternating voltage to the stator, which from then on
he can produce a rotating magnetic field that runs through the rotor conductors.
This variable magnetic field induces an electromotive force (emf) in the rotor that, in turn, creates its own rotating magnetic field. The rotating magnetic field created by the rotor, when “trying” to align with the rotating field of the stator, produces a rotational movement in the rotor, that is, the rotor starts to rotate continuously, and the motor speed is inversely proportional to the number of poles it has, that is, the greater the number of poles of the motor, the lower its speed will be.
In the video below we show better how this motor speed is related to the number of poles it has.
It is important to note that the rotor speed of rotation is slightly lower than the rotational speed of the rotating field of the stator, so the rotor is not synchronized with this rotating field, hence the name asynchronous motor.