The synchronous motor needs to have its speed of rotation constant and identical to the speed of the rotating field, which is known as synchronous speed. The only way to make this happen is to ensure that the rotor is a fixed polarity electromagnet with constant field so that it does not follow the variations of the stator field and for that we will use a rotor similar to the motor rotor of direct current. The rotor is winded, rather than caged, and this format prevents induced currents from occurring.
The rotor is made in this way, 3 horsepower 182T frame so that we can inject into it direct current, and magnetize it to create an electromagnet of fixed poles. The next step is to make it spin, which by itself does not occur due to the fast spinning rotating field speed. Therefore, it is necessary to accelerate the rotor up to about 95% of the synchronous speed and, in this way to apply the direct current that will cause it to rotate the synchronous speed, only with a small constant angle of difference, the so-called torque angle. If a greater load is taken than the synchronous motor is able to drive and the torque angle grows too much, the motor will be turned off.