The synchronous motor is the motor with the same speed as the synchronous speed (the speed of the asynchronous motor has a certain difference between the speed and the synchronous speed of the asynchronous motor). It is mainly used as a generator, and it is also used for driving motor of large machinery, such as rolling mill, compressor, blower, ball mill and so on. In addition, it is also used as the regulator of the power grid to adjust the reactive power of the power grid.
All the rotor of the synchronous motor is a wire winding type, with a brush and a collector ring. The structure is complex and the cost is high. The magnetic field of the rotor is built on the external power supply. Rotor asynchronous motor can be wound, but the vast majority of squirrel cage rotor magnetic field, simple structure, stator magnetic induction, magnetic synchronous speed ratio of low speed, only the relative movement between the only way of the rotor and the stator synchronous magnetic field, can induce an electric current, and a magnetic field in the interaction the rotor magnetic field, rotation.