The rotor of the electric motor so that it can work, needs a torque so that it can begin its turning. This torque is normally developed by magnetic forces generated between the rotor and stator magnetic poles. An engine can never operate if it is designed solely with permanent magnets and this factor is easy to verify, since not only will it not have the initial torque to start the movement, if they are already in their equilibrium positions, as they will only hesitate, around this position if they have an initial impulse.
The attraction or repulsion forces generated between stator and rotor can pull or push the movable poles of the rotor, thereby producing torques, which will cause the rotor to rotate faster, until the frictions or charges attached to the rotor. shaft can reduce the resulting torque to zero. motor brakes
Both the rotor and the stator of the electric motor need to be magnetic, since these forces are between the poles that cause the necessary torque to make the rotor rotate. However, even if permanent magnets are often used, especially small motors, at least some of the magnets on an engine will need to be electromagnets.
The year 1886 is considered the year of birth of the electric machine, as it was on this date that the German scientist Werner Von Siemens, idealized the first self induced inductive current generator. This electric machine in a few years, revolutionized the world, was invented in the last period of studies, inventions and research of many other scientists in a great period, of approximately three centuries.
In 1600, the English scientist William Gilbert published in London a work called Magnete, which described the force of magnetic attraction. The great landmark of static electricity had previously been verified by the Greek Tales in 641 BC Tales proved that by rubbing a piece of amber with a piece of cloth, the piece obtained the property of being able to attract light bodies such as leaves, dust , hair and feathers.
The first electrostatic machine was designed in 1663, by the German Otto Von Guericke, being perfected some time later, in the middle of 1775, by the Swiss Martin Plant. When the Danish physicist Hans Christian Oersted experimented with electric currents, it was possible to ascertain in 1820 that the magnetic compass needle was diverted from its original north-south position as it passed near a conductor in the which circulated an electric current.