The three-phase motor is made of a stator with grooves inside it, where several coils are housed perfectly isolated from the stator mass and each other, properly distributed and connected forming three distinct and symmetrical circuits called phases. These phases must be connected in triangle (Δ) or star (Υ) to a three-phase network so that their coils cause a resulting rotating 8078-j alemite field of invariable value. The most common three-phase motor of application has the squirrel cage type rotor, and can also be winding type with rings to control starting by means of rheostat.
We can express the following principle of operation: three identical windings A, B and C symmetrically placed with their respective axes at 120 ° to each other, traversed by three alternating currents of equal frequency and effective value, but out of phase with each other of 120 ° electrical or 1 / 3, produce a rotating magnetic field φ R with constant amplitude, equal to 1.5 times the maximum value of each of the three component fields φA, φB and φC. The rotating field when crossing the bars or conductors produces in these currents induced, causing the rotor to create a magnetic field that accompanies its direction of rotation.