AC gearmotors
Introduction
The asynchronous motor or induction motor is an alternating current electric motor, in which its rotor rotates at a speed different from that of the stator's magnetic field.
The three-phase asynchronous motor is made up of a rotor, which can be of two types: a) squirrel cage; b) winding, and a stator, in which the inductor coils are located. These coils are three-phase and are out of phase with each other by 120° in space. According to the Ferraris theorem, when a system of balanced three-phase currents circulates through these coils, whose phase difference in time is also 120°, a rotating magnetic field is induced that surrounds the rotor. This variable magnetic field will induce an electrical voltage in the rotor according to Faraday's law of induction:
The difference between the induction motor and the universal motor is that in the induction motor the rotor winding is not connected to the motor's excitation circuit but is electrically isolated. It has driving bars along its entire length, embedded in slots at uniform distances around the periphery. The bars are connected with rings (shorted) to each end of the rotor. They are welded to the ends of the bars. This assembly resembles small rotating cages for exercising pets such as hamsters and is therefore sometimes called a "squirrel cage", and induction motors are called squirrel cage motors.
Then the Laplace effect (or motor effect) occurs: every conductor through which an electric current circulates, immersed in a magnetic field, experiences a force that tends to set it in motion. Simultaneously, the Faraday effect (or generating effect) occurs: a voltage is induced in any conductor that moves within a magnetic field.
The rotating magnetic field, at synchronous speed, created by the stator winding, cuts the rotor conductors, generating an induction magnetomotive force.
The mutual action of the rotating field and the currents existing in the rotor conductors create an electrodynamic force on said rotor conductors, which make the motor rotor rotate.
The difference between the speeds of the rotor and the magnetic field is called slip or slip.
History
In 1824, the French physicist François Arago formulated the existence of rotating magnetic fields, called Arago rotations. In 1879, Walter Baily) demonstrated that, by manually turning switches on and off, this was the first primitive induction motor.[1][2][3][4][5][6][7][8].