INDUCTION OF MOVEMENT

The above information tells us that two magnets experience a force of attraction or repulsion when they are, each, falling within the scope of the other.

We also learned how to implement electro-magnets by a magnetic core, copper wire winding and a source of DC or AC power.

It is therefore concluded that, if we place an electro-magnet in the magnetic field of another, as shown in Figure 8, and fed with current copper wire (a coil), it will experience a force in the sense indicated by the thumb of his right hand. Such is the working principle underlying the DC electric motors.

Figure 8 - Motion Induction Principles

In the case of motion induction AC motor, the operating principle is based on the production of a rotating magnetic field. Considering that the magnet of Figure 9 with its NS poles can rotate on the axis XY, and a disc of copper or aluminum is subjected to the magnetic field of the magnet, you can also turn on the same axis, then we must, if you turn the magnet, its magnetic field also rotates, sweeping the drive next to it, which the field is now variable, is the cause that under the principles of magnetic induction, appear on the disc induced currents. These currents react producing a magnetomotive force motor with enough torque to overcome the resistant torque of the shaft and cause the rotation of the disc.

Figure 9 - magnet with its poles NS spinning on the axis XY

A practical way to generate a rotating magnetic field is achieved by feeding, three-phase alternating voltage of a winding phase also installed on a core of magnetic material called "stator", as shown in Figure 10.

Figure 10 - Food with a three-phase alternating voltage three-phase winding (stator)

At the speed of rotation of the magnetic field is called "synchronous speed". This rotating magnetic field cuts the aluminum rods "rotor" which is installed inside the stator, see Figure 11 on which the rotor induces a current that in turn cause a rotor magnetic field, producing an interaction of fields and causing the rotor to rotate in the same direction as the stator's magnetic field, but at a rate slightly less than synchronous. We shall see that the difference of these speeds is called "slip".

Figure 11