What's the difference between asynchronous and synchronous AC motors?
Asynchronous motors and synchronous machines actually have a big difference in principle:The synchronous motor works by "the magnetic field always goes along the shortest direction of the magnetic circuit", taking the transition motor as an example. When there is excitation on the rotor, the N and S poles appear; then the stator magnetic field rotates, and its N and S poles change with each other, and always correspond to the magnetic poles of the rotor. So synchronization is formed. What's more, the number of poles of the stator and rotor must be the same, otherwise the motor will not work.
The two main difference in the reactive power, synchronous motor, and reactive power can be issued, you can also absorb the collection; asynchronous motor can only absorb reactive power. The synchronous motor turns to synchronize with the power grid. The speed of the asynchronous motor is generally slightly lower than the speed of the grid. Synchronous motor speed and AC power 50Hz synchronous power, that is, 2 pole motor 3000 turn, 4 pole 1500, 6 pole 1000, etc., asynchronous motor speed is slightly behind, that is, 2 poles, 2880, 4 poles, 1440, 6, pole 960, etc..
The induction motor is realized by induction. The principle is that in the stator winding with three-phase voltage, will form a rotating magnetic field, the rotor on the lead because of cutting lines of force, so the potential, and because the guide bar is connected, so produce the current. At this point, we think of what we learned in junior high school -- "electrified conductors produce motion in a magnetic field."". So this kind of motor is called induction motor". For asynchronous or induction machines, the number of poles of the rotor is automatically induced by the number of poles of the stator. It can also be said that the rotor is not polar. (above is an example of armature winding on the stator). There is no pivot / transition for asynchronous motors.
The so-called synchronous motor, that is, the armature winding magnetic field, rotating speed and rotor rotation in the same direction, the same speed. Such a motor is generally as follows: there is a winding on the rotor, a centralized excitation winding; no winding on the rotor; and the use of permanent magnet structure; rotor without winding; no permanent magnet; with teeth and slots. A distributed winding is arranged on the stator. With this structure, the number of slip rings and brushes can be reduced to a minimum. Such motors are also called transition motors. There is also a special requirement, and the excitation windings placed on the stator structure, such a structure is generally referred to as pivot type (such as home ceiling fan).
