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Electric motor

Electric Motor, Types and Operation

Electric motor, types and operation

The electric motor is an electrotechnical machine that converts electrical energy into mechanical energy. That is, when the electric motor is connected to the appropriate power source, it begins to rotate, which also begins to rotate the machine or the machine associated with it. That is, it works in reverse to the electric generator, which produces electrical energy with mechanical energy.

The electric motor was made possible by the discoveries of Franz Ernst Neumann and James Clerk Maxwell. His discoveries were published in the years 1841 and 1873.

What Are the Types of Electric Motors?

Electric motors can be distinguished between them according to the type of supply current:

  • DC electric motors.
  • Alternating current electric motors.

The direct current electric motor can be, in turn, a permanent induction motor or a continuous induction motor. On the other hand, the alternating current motor can be classified into universal motor, synchronous motor or asynchronous motor. In addition to these more general classifications, there are also other more modern types of motor such as stepper motors and linear motors.

How Does an Electric Engine Work?

How does an electric engine work? The operation of an electric motor varies according to the type of motor of which they are part.

Operation of a Direct Current Motor with Permanent Induction

The DC motor is the simplest motor. Going from the outside of the engine to the inside we find:

  • The casing or crankcase, which has a fixing system to the bench or chassis. In the crankcase there is a set called a stator or inductor that is made up of a plate support and some magnets or electromagnets.
  • The rotor, which is made up of a core of sheets on a shaft that supports everything. The shaft is surrounded by a series of windings that are connected to the manifold strips. The electric current is received through the collector slits. All of this is supported by the bearings at the ends of the crankcase.
  • On one side of the shaft is the pulley. The pulley is a toothed ring or coupling that transmits mechanical energy to be used.

When the current is passed through the brushes to the collector, an electric current is passed through the conductors of the coils, which by the rule of the left hand (remember that they are submerged in the stator field), creates a force lateral, and the sum of all of them gives us the torque that makes the rotor or motor assembly rotate. Through the collector, current is given to the appropriate coils so that this pair is as strong as possible. They are the motors that are in devices that are moved by cells or batteries.

DC Motor with Variable Induction and Universal Alternating Current

It is the same as the motor with permanent induction, but in this case what produces the field are coils that work like an electromagnet, and are connected to the rotor in series or parallel. This motor also works with single-phase alternating current. The most common example is the motors of household appliances in normal use.

Asynchronous AC Electric Motor

In an asynchronous motor, there are three groups of windings in the stator. These windings correspond to the three phases of commercial alternating current, and the rotor instead of the collector, carries three rings, which are connected to the rotor windings. This type of electric motor works by the same principle, although due to the displacement between phases, a rotating field is produced, which in a way drives the rotor.

A very widely used particular case is the squirrel cage motor, since it is a very simple motor. In which the thin and windings of the rotor are replaced by rods with rings at the ends joining the rods, hence its name.

In asynchronous alternating current motors, the windings can be connected in two ways: In star, when one end of the coils is common and the other connected to each of the phases. The other is in triangle, when the ends of the coils are connected to each other and in one phase. The exchange of two phases causes a reversal of the direction of rotation.

It is the most commonly used engine in the industry, with the star delta starting system.

Synchronous Alternating Current Electric Motor

The synchronous motor is so named because the speed of rotation is related to the frequency of the supply current. This characteristic is due to the fact that the rotor is supplied with direct current, and is driven by the rotating field produced by the stator coils.

Normally this alternating current motor has a dynamo coupled on the same motor shaft to power the rotor. As the speed varies with the frequency and that allows to fix the motor torque with a minimum consumption, by being coupled to an oscillator its speed can be varied very easily, and therefore it is used in traction systems (AVE-TGV).

Stepper Motor

The stepper motor is powered by direct current, and the rotor contains a series of permanent magnets, which are driven by the stator coils, which are governed by power electronics, determining the angle of rotation, which have proportional control. , are extremely precise in the angle of rotation, or position. These motors are widely used in the motion servos of numerical control machines, or in the read / write motors of computer hard drives.

Linear Motor

In a basic way, a linear motor is an asynchronous motor that has been developed, so instead of creating a rotating torque, it creates a linear displacement, due to the displacement of the phases. These engines are divided into two large groups:

  • Those of slow acceleration that are used in transport Sky Train, Maglev, etc.
  • Rapid acceleration DE used in weapons such as the magnetic cannon and space artifacts.

Within the same category and are the electromagnetic induction pumps that allow conductive fluids to circulate. The first tests were made with mercury, then with a mixture of sodium and potassium, in view of the circulation of sodium for cooling in some nuclear power plants.

History of Electric Motors

In 1821, following the discovery of the phenomenon of electromagnetism by the Danish chemist Hans Christian Ørsted, the English physicist Michael Faraday built two devices to produce what he called an electromagnetic rotation. These devices consist of the continuous circular movement of a magnetic field around a wire. When making the demonstration, the first description was that of the current electric motor, alternating current, patented in 1887 by the Serbian physicist Nikola Tesla.

In 1822, Peter Barlow created the Barlow wheel. Barlow's wheel is a widget that consists of a metal disk cut into a star, the extremities of the star are submerged in an air gap containing mercury. The function of mercury is to ensure the passage of current.

The first usable switch was invented in 1832 by William Sturgeon. Later, in 1834, Mr. Thomas Davenport made a direct current motor with this invention. The direct current motor was patented in 1837. The high cost of the batteries did not allow these electric motors to have a significant initial success.

It is not very clear who is the father of asynchronous machines. This title is disputed by three inventors: Nikola Tesla, Galileo Ferraris and Michail Ossipowitsch.

In 1887 the physicist Nikola Tesla filed a patent on the asynchronous machine. The following year he filed 5 more patents for an asynchronous electrical machine. Meanwhile, Galileo Ferraris published treatises on rotating machines.

In 1885 Ferraris published an experiment and subsequently published a theory about the asynchronous motor in April 1888. Finally, in 1889 a German electrician of Russian origin named Michail Ossipowitsch Doliwo-Dobrowolski invented the first asynchronous three-phase current squirrel cage motor. . This last electric motor was industrially built starting in 1891.

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Published: November 10, 2016
Last review: November 23, 2018