Electric motors are electric machines that somehow are part of our daily lives, as there are infinite applications for electric motors. They can be used in drills, lathes, conveyors, hair clippers, microwaves, refrigerators, computers, printers, drones, robots, vacuum cleaners, elevators and etc.
Due to the importance and huge variety of electric motors available, the World of Electrical created this article to talk about the main types of electric motors. We approach what are direct current (DC) and alternating current (AC) motors, their main characteristics and mainly we present the main types of motors such as dahlander motor, stepper motor, servo motor, brushless motor, among others. Come on, guys!
Electric motors are electrical machines that have the characteristic of transforming electrical energy into mechanical energy. There are many types of electric motors, and we can basically separate them into three major groups, which are direct current motors, alternating current motors and universal motors. For each of these types of motors mentioned, there are other motor separations such as alternating current motors, which can be synchronous motors or asynchronous motors. In the image below we can better observe which are the engine ratings.
Main types of electric motors, what are they?
Classifications for electric motors.
Alternating current (AC) motors
When we talk about alternating current motors we imagine various types of motors such as lathes, cutters, moving walkways, escalators, elevators, electric gates, fans, vacuum cleaners, etc. There are many types of motors (AC), whether single-phase or three-phase, each with their own characteristics and different applications, as we will see below.
AC motors: Single-phase
Single-phase motors are motors powered by only one phase conductor and are generally used when there is no three-phase network available at the installation. For this reason, they are widely used for domestic and commercial purposes and in a few situations, they are used in the industry. Typically single-phase electric motors are used in applications that require less power, generally less than 3KW.
The construction of single-phase motors is relatively simple, as they have a lower cost and are easy to repair compared to three-phase motors. Because of this and other advantages, the single-phase motor has many applications, being used in vacuum cleaners, fans, washing machines, refrigerators, some centrifugal pumps, etc.
It is important to note that single-phase motors are unable to start on their own as with three-phase motors, so an auxiliary component is required to allow the motor to start. its operation. This component that helps the single-phase motor to start is the capacitor, with some motors having a permanent capacitor and others using an exclusive capacitor when starting. We can mention as an example the motors that have a centrifugal switch, which removes the capacitor after the motor reaches a certain speed.
AC motors: Three-phase
The alternating current (AC) motor, which is also known as the induction motor, is the most widely used due to its several advantages, such as the low cost of maintenance, assembly, manufacture and simplicity in relation to direct current motors.
The operation of the induction motor is based on the creation of a rotating magnetic field, or rotating field. An alternating voltage applied to the motor stator creates a rotating field, which from then on produces a rotating magnetic field that passes through the rotor conductors. This rotating magnetic field created by the rotor tries to align itself with the rotating field of the stator, which produces a rotational movement in the rotor.
Three-phase electric motors can be easily found in industries for the most varied applications such as lathe, milling machine, conveyor belts, in addition to other applications outside industries, such as elevators and escalators.
AC motors: Synchronous
Alternating current motors can also be classified into synchronous motors and asynchronous motors, in addition, to single-phase or three-phase motors. The main difference between them is that asynchronous motor spins at a constant speed, regardless of the variation in loads. This speed is known as synchronous speed, and this is because the speed of the rotating magnetic field depends on the frequency of the alternating network (AC).
Because the network frequency is constant, synchronous motors are in practice single speed motors and if we observe asynchronous motor, there is no electromotive force (fem) induced in the motor rotor, because there is no relative movement between the rotating field and the rotor.
It is important to point out that one of the disadvantages of the pure synchronous motor is that it cannot start from a rest position just by applying a three-phase AC voltage to the stator. Because the synchronous motor does not have its own start, it needs a device that makes the rotor rotate until it reaches synchronous speed.
The simplest way to start a synchronous motor is to use another motor, which can be alternating current (AC) or direct current (DC). This other auxiliary motor is coupled to the asynchronous motor axis so that it drags it until it reaches synchronous speed.
Main types of electric motors, what are they?
Several types of electric motors.
Alternating current motors: Asynchronous
Unlike the synchronous motor, the asynchronous motor rotates at a speed slightly less than the rotation speed of the rotating field of the stator. Therefore, the rotor is not synchronized with this rotating field, so it is called an asynchronous motor. This difference between the speed of the rotor and the speed of the magnetic field is called the slip of the motor. To better understand the operation and applications of asynchronous motors, here on the Mundo da Elétrica website we have a complete article on the three-phase induction motor . Below is an example of an AC motor.
The Dahlander Motor is a type of three-phase asynchronous electric motor. It has two distinct speeds and can be used in various situations within the industry, such as cranes, winches, conveyors, machines and equipment that require an asynchronous motor. In this type of engine, the greater the number of poles, the lower the speed,