Three phase ac synchronous motor is different from three-phase ac asynchronous motor
use Synchronous motors are used mostly in large generators, while asynchronous motors are used almost exclusively in motor situations. The synchronous motor can adjust the power factor by the excitation. The power factor of asynchronous motor is adjustable, so in some large factories, application of asynchronous motor is large, can be added a synchronous motor for condenser, used to adjust the plant and the power factor of power network interface. However, due to the synchronous motor of high cost, maintenance workload is big, now commonly used capacitance compensation power factor. Synchronous machine with exciting winding and the slip ring, need the operator had a higher level to control excitation, in addition, compared with those of asynchronous machine maintenance free maintenance workload is bigger; So, as an electric motor, most current asynchronous motors are chosen.
Structure and principle of The stator winding of synchronous motor and asynchronous motor is the same, the main difference is the structure of the rotor. The rotor of synchronous motor has dc excitation winding, so it needs to be coupled with excitation power supply to introduce current through the slide ring. The rotor of the asynchronous motor is a short-circuit winding, which generates an electric current through the electromagnetic induction. Asynchronous motor is simple, low cost, easy to install, use and maintenance. It has been widely used. Disadvantages low efficiency, low power factor of power grids. And synchronous motor with high efficiency is the capacitive load, can improve the power factor of power grid. Multi-purpose mining large not ready.
Asynchronous motor stator into alternating current (ac), is to produce a rotating magnetic field, and the rotor magnetic fields generated by induction, so that the two magnetic field effect, make the rotor turns with the stator's rotating magnetic field. The rotor is slower than the stator rotating magnetic field, a slip, sync so called asynchronous machine. The rotor of synchronous motor is made by adding direct current to the same magnetic field, so that the rotor will follow the stator rotating field to synchronize with the other.
